Setup swipe for all directions

1 files changed, 1515 insertions, 0 deletions

diff --git a/core/src/main/kotlin/ca/allanwang/kau/swipe/ViewDragHelper.java b/core/src/main/kotlin/ca/allanwang/kau/swipe/ViewDragHelper.java
new file mode 100644
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--- /dev/null
+++ b/core/src/main/kotlin/ca/allanwang/kau/swipe/ViewDragHelper.java
@@ -0,0 +1,1515 @@
+package ca.allanwang.kau.swipe;
+
+/**
+ * Created by Allan Wang on 2017-07-05.
+ */
+
+import android.content.Context;
+import android.support.v4.view.ViewCompat;
+import android.util.Log;
+import android.view.MotionEvent;
+import android.view.VelocityTracker;
+import android.view.View;
+import android.view.ViewConfiguration;
+import android.view.ViewGroup;
+import android.view.animation.Interpolator;
+import android.widget.OverScroller;
+
+import java.util.Arrays;
+
+/**
+ * ViewDragHelper is a utility class for writing custom ViewGroups. It offers a number
+ * of useful operations and state tracking for allowing a user to drag and reposition
+ * views within their parent ViewGroup.
+ * <p>
+ * This is an extension of {@link android.support.v4.widget.ViewDragHelper}
+ * Along with additional methods defined in
+ */
+public class ViewDragHelper implements ViewDragHelperExtras {
+    private static final String TAG = "ViewDragHelper";
+
+    /**
+     * A null/invalid pointer ID.
+     */
+    public static final int INVALID_POINTER = -1;
+
+    /**
+     * A view is not currently being dragged or animating as a result of a fling/snap.
+     */
+    public static final int STATE_IDLE = 0;
+
+    /**
+     * A view is currently being dragged. The position is currently changing as a result
+     * of user input or simulated user input.
+     */
+    public static final int STATE_DRAGGING = 1;
+
+    /**
+     * A view is currently settling into place as a result of a fling or
+     * predefined non-interactive motion.
+     */
+    public static final int STATE_SETTLING = 2;
+
+    /**
+     * Edge flag indicating that the left edge should be affected.
+     */
+    public static final int EDGE_LEFT = 1 << 0;
+
+    /**
+     * Edge flag indicating that the right edge should be affected.
+     */
+    public static final int EDGE_RIGHT = 1 << 1;
+
+    /**
+     * Edge flag indicating that the top edge should be affected.
+     */
+    public static final int EDGE_TOP = 1 << 2;
+
+    /**
+     * Edge flag indicating that the bottom edge should be affected.
+     */
+    public static final int EDGE_BOTTOM = 1 << 3;
+
+    /**
+     * Edge flag set indicating all edges should be affected.
+     */
+    public static final int EDGE_ALL = EDGE_LEFT | EDGE_TOP | EDGE_RIGHT | EDGE_BOTTOM;
+
+    /**
+     * Indicates that a check should occur along the horizontal axis
+     */
+    public static final int DIRECTION_HORIZONTAL = 1 << 0;
+
+    /**
+     * Indicates that a check should occur along the vertical axis
+     */
+    public static final int DIRECTION_VERTICAL = 1 << 1;
+
+    /**
+     * Indicates that a check should occur along all axes
+     */
+    public static final int DIRECTION_ALL = DIRECTION_HORIZONTAL | DIRECTION_VERTICAL;
+
+    private static final int EDGE_SIZE = 20; // dp
+
+    private static final int BASE_SETTLE_DURATION = 256; // ms
+    private static final int MAX_SETTLE_DURATION = 600; // ms
+
+    // Current drag state; idle, dragging or settling
+    private int mDragState;
+
+    // Distance to travel before a drag may begin
+    private int mTouchSlop;
+
+    // Last known position/pointer tracking
+    private int mActivePointerId = INVALID_POINTER;
+    private float[] mInitialMotionX;
+    private float[] mInitialMotionY;
+    private float[] mLastMotionX;
+    private float[] mLastMotionY;
+    private int[] mInitialEdgesTouched;
+    private int[] mEdgeDragsInProgress;
+    private int[] mEdgeDragsLocked;
+    private int mPointersDown;
+
+    private VelocityTracker mVelocityTracker;
+    private float mMaxVelocity;
+    private float mMinVelocity;
+
+    private int mEdgeSize;
+    private int mTrackingEdges;
+
+    private OverScroller mScroller;
+
+    private final ViewDragHelper.Callback mCallback;
+
+    private View mCapturedView;
+    private boolean mReleaseInProgress;
+
+    private final ViewGroup mParentView;
+
+    /**
+     * A Callback is used as a communication channel with the ViewDragHelper back to the
+     * parent view using it. <code>on*</code>methods are invoked on siginficant events and several
+     * accessor methods are expected to provide the ViewDragHelper with more information
+     * about the state of the parent view upon request. The callback also makes decisions
+     * governing the range and draggability of child views.
+     */
+    public abstract static class Callback {
+        /**
+         * Called when the drag state changes. See the <code>STATE_*</code> constants
+         * for more information.
+         *
+         * @param state The new drag state
+         * @see #STATE_IDLE
+         * @see #STATE_DRAGGING
+         * @see #STATE_SETTLING
+         */
+        public void onViewDragStateChanged(int state) {
+        }
+
+        /**
+         * Called when the captured view's position changes as the result of a drag or settle.
+         *
+         * @param changedView View whose position changed
+         * @param left        New X coordinate of the left edge of the view
+         * @param top         New Y coordinate of the top edge of the view
+         * @param dx          Change in X position from the last call
+         * @param dy          Change in Y position from the last call
+         */
+        public void onViewPositionChanged(View changedView, int left, int top, int dx, int dy) {
+        }
+
+        /**
+         * Called when a child view is captured for dragging or settling. The ID of the pointer
+         * currently dragging the captured view is supplied. If activePointerId is
+         * identified as {@link #INVALID_POINTER} the capture is programmatic instead of
+         * pointer-initiated.
+         *
+         * @param capturedChild   Child view that was captured
+         * @param activePointerId Pointer id tracking the child capture
+         */
+        public void onViewCaptured(View capturedChild, int activePointerId) {
+        }
+
+        /**
+         * Called when the child view is no longer being actively dragged.
+         * The fling velocity is also supplied, if relevant. The velocity values may
+         * be clamped to system minimums or maximums.
+         * <p>
+         * <p>Calling code may decide to fling or otherwise release the view to let it
+         * settle into place. It should do so using {@link #settleCapturedViewAt(int, int)}
+         * or {@link #flingCapturedView(int, int, int, int)}. If the Callback invokes
+         * one of these methods, the ViewDragHelper will enter {@link #STATE_SETTLING}
+         * and the view capture will not fully end until it comes to a complete stop.
+         * If neither of these methods is invoked before <code>onViewReleased</code> returns,
+         * the view will stop in place and the ViewDragHelper will return to
+         * {@link #STATE_IDLE}.</p>
+         *
+         * @param releasedChild The captured child view now being released
+         * @param xvel          X velocity of the pointer as it left the screen in pixels per second.
+         * @param yvel          Y velocity of the pointer as it left the screen in pixels per second.
+         */
+        public void onViewReleased(View releasedChild, float xvel, float yvel) {
+        }
+
+        /**
+         * Called when one of the subscribed edges in the parent view has been touched
+         * by the user while no child view is currently captured.
+         *
+         * @param edgeFlags A combination of edge flags describing the edge(s) currently touched
+         * @param pointerId ID of the pointer touching the described edge(s)
+         * @see #EDGE_LEFT
+         * @see #EDGE_TOP
+         * @see #EDGE_RIGHT
+         * @see #EDGE_BOTTOM
+         */
+        public void onEdgeTouched(int edgeFlags, int pointerId) {
+        }
+
+        /**
+         * Called when the given edge may become locked. This can happen if an edge drag
+         * was preliminarily rejected before beginning, but after {@link #onEdgeTouched(int, int)}
+         * was called. This method should return true to lock this edge or false to leave it
+         * unlocked. The default behavior is to leave edges unlocked.
+         *
+         * @param edgeFlags A combination of edge flags describing the edge(s) locked
+         * @return true to lock the edge, false to leave it unlocked
+         */
+        public boolean onEdgeLock(int edgeFlags) {
+            return false;
+        }
+
+        /**
+         * Called when the user has started a deliberate drag away from one
+         * of the subscribed edges in the parent view while no child view is currently captured.
+         *
+         * @param edgeFlags A combination of edge flags describing the edge(s) dragged
+         * @param pointerId ID of the pointer touching the described edge(s)
+         * @see #EDGE_LEFT
+         * @see #EDGE_TOP
+         * @see #EDGE_RIGHT
+         * @see #EDGE_BOTTOM
+         */
+        public void onEdgeDragStarted(int edgeFlags, int pointerId) {
+        }
+
+        /**
+         * Called to determine the Z-order of child views.
+         *
+         * @param index the ordered position to query for
+         * @return index of the view that should be ordered at position <code>index</code>
+         */
+        public int getOrderedChildIndex(int index) {
+            return index;
+        }
+
+        /**
+         * Return the magnitude of a draggable child view's horizontal range of motion in pixels.
+         * This method should return 0 for views that cannot move horizontally.
+         *
+         * @param child Child view to check
+         * @return range of horizontal motion in pixels
+         */
+        public int getViewHorizontalDragRange(View child) {
+            return 0;
+        }
+
+        /**
+         * Return the magnitude of a draggable child view's vertical range of motion in pixels.
+         * This method should return 0 for views that cannot move vertically.
+         *
+         * @param child Child view to check
+         * @return range of vertical motion in pixels
+         */
+        public int getViewVerticalDragRange(View child) {
+            return 0;
+        }
+
+        /**
+         * Called when the user's input indicates that they want to capture the given child view
+         * with the pointer indicated by pointerId. The callback should return true if the user
+         * is permitted to drag the given view with the indicated pointer.
+         * <p>
+         * <p>ViewDragHelper may call this method multiple times for the same view even if
+         * the view is already captured; this indicates that a new pointer is trying to take
+         * control of the view.</p>
+         * <p>
+         * <p>If this method returns true, a call to {@link #onViewCaptured(android.view.View, int)}
+         * will follow if the capture is successful.</p>
+         *
+         * @param child     Child the user is attempting to capture
+         * @param pointerId ID of the pointer attempting the capture
+         * @return true if capture should be allowed, false otherwise
+         */
+        public abstract boolean tryCaptureView(View child, int pointerId);
+
+        /**
+         * Restrict the motion of the dragged child view along the horizontal axis.
+         * The default implementation does not allow horizontal motion; the extending
+         * class must override this method and provide the desired clamping.
+         *
+         * @param child Child view being dragged
+         * @param left  Attempted motion along the X axis
+         * @param dx    Proposed change in position for left
+         * @return The new clamped position for left
+         */
+        public int clampViewPositionHorizontal(View child, int left, int dx) {
+            return 0;
+        }
+
+        /**
+         * Restrict the motion of the dragged child view along the vertical axis.
+         * The default implementation does not allow vertical motion; the extending
+         * class must override this method and provide the desired clamping.
+         *
+         * @param child Child view being dragged
+         * @param top   Attempted motion along the Y axis
+         * @param dy    Proposed change in position for top
+         * @return The new clamped position for top
+         */
+        public int clampViewPositionVertical(View child, int top, int dy) {
+            return 0;
+        }
+    }
+
+    /**
+     * Interpolator defining the animation curve for mScroller
+     */
+    private static final Interpolator sInterpolator = new Interpolator() {
+        @Override
+        public float getInterpolation(float t) {
+            t -= 1.0f;
+            return t * t * t * t * t + 1.0f;
+        }
+    };
+
+    private final Runnable mSetIdleRunnable = new Runnable() {
+        @Override
+        public void run() {
+            setDragState(STATE_IDLE);
+        }
+    };
+
+    /**
+     * Factory method to create a new ViewDragHelper.
+     *
+     * @param forParent Parent view to monitor
+     * @param cb        Callback to provide information and receive events
+     * @return a new ViewDragHelper instance
+     */
+    public static ViewDragHelper create(ViewGroup forParent, ViewDragHelper.Callback cb) {
+        return new ViewDragHelper(forParent.getContext(), forParent, cb);
+    }
+
+    /**
+     * Factory method to create a new ViewDragHelper.
+     *
+     * @param forParent   Parent view to monitor
+     * @param sensitivity Multiplier for how sensitive the helper should be about detecting
+     *                    the start of a drag. Larger values are more sensitive. 1.0f is normal.
+     * @param cb          Callback to provide information and receive events
+     * @return a new ViewDragHelper instance
+     */
+    public static ViewDragHelper create(ViewGroup forParent, float sensitivity, ViewDragHelper.Callback cb) {
+        final ViewDragHelper helper = create(forParent, cb);
+        helper.mTouchSlop = (int) (helper.mTouchSlop * (1 / sensitivity));
+        return helper;
+    }
+
+    /**
+     * Apps should use ViewDragHelper.create() to get a new instance.
+     * This will allow VDH to use internal compatibility implementations for different
+     * platform versions.
+     *
+     * @param context   Context to initialize config-dependent params from
+     * @param forParent Parent view to monitor
+     */
+    private ViewDragHelper(Context context, ViewGroup forParent, ViewDragHelper.Callback cb) {
+        if (forParent == null) {
+            throw new IllegalArgumentException("Parent view may not be null");
+        }
+        if (cb == null) {
+            throw new IllegalArgumentException("Callback may not be null");
+        }
+
+        mParentView = forParent;
+        mCallback = cb;
+
+        final ViewConfiguration vc = ViewConfiguration.get(context);
+        final float density = context.getResources().getDisplayMetrics().density;
+        mEdgeSize = (int) (EDGE_SIZE * density + 0.5f);
+
+        mTouchSlop = vc.getScaledTouchSlop();
+        mMaxVelocity = vc.getScaledMaximumFlingVelocity();
+        mMinVelocity = vc.getScaledMinimumFlingVelocity();
+        mScroller = new OverScroller(context, sInterpolator);
+    }
+
+    /**
+     * Set the minimum velocity that will be detected as having a magnitude greater than zero
+     * in pixels per second. Callback methods accepting a velocity will be clamped appropriately.
+     *
+     * @param minVel Minimum velocity to detect
+     */
+    public void setMinVelocity(float minVel) {
+        mMinVelocity = minVel;
+    }
+
+    /**
+     * Return the currently configured minimum velocity. Any flings with a magnitude less
+     * than this value in pixels per second. Callback methods accepting a velocity will receive
+     * zero as a velocity value if the real detected velocity was below this threshold.
+     *
+     * @return the minimum velocity that will be detected
+     */
+    public float getMinVelocity() {
+        return mMinVelocity;
+    }
+
+    @Override
+    public void setMaxVelocity(float maxVel) {
+        mMaxVelocity = maxVel;
+    }
+
+    @Override
+    public float getMaxVelocity() {
+        return mMaxVelocity;
+    }
+
+    /**
+     * Retrieve the current drag state of this helper. This will return one of
+     * {@link #STATE_IDLE}, {@link #STATE_DRAGGING} or {@link #STATE_SETTLING}.
+     *
+     * @return The current drag state
+     */
+    public int getViewDragState() {
+        return mDragState;
+    }
+
+    /**
+     * Enable edge tracking for the selected edges of the parent view.
+     * The callback's {@link ViewDragHelper.Callback#onEdgeTouched(int, int)} and
+     * {@link ViewDragHelper.Callback#onEdgeDragStarted(int, int)} methods will only be invoked
+     * for edges for which edge tracking has been enabled.
+     *
+     * @param edgeFlags Combination of edge flags describing the edges to watch
+     * @see #EDGE_LEFT
+     * @see #EDGE_TOP
+     * @see #EDGE_RIGHT
+     * @see #EDGE_BOTTOM
+     */
+    public void setEdgeTrackingEnabled(int edgeFlags) {
+        mTrackingEdges = edgeFlags;
+    }
+
+    /**
+     * Return the size of an edge. This is the range in pixels along the edges of this view
+     * that will actively detect edge touches or drags if edge tracking is enabled.
+     *
+     * @return The size of an edge in pixels
+     * @see #setEdgeTrackingEnabled(int)
+     */
+    public int getEdgeSize() {
+        return mEdgeSize;
+    }
+
+    @Override
+    public void setEdgeSize(int size) {
+        mEdgeSize = size;
+    }
+
+    /**
+     * Capture a specific child view for dragging within the parent. The callback will be notified
+     * but {@link ViewDragHelper.Callback#tryCaptureView(android.view.View, int)} will not be asked permission to
+     * capture this view.
+     *
+     * @param childView       Child view to capture
+     * @param activePointerId ID of the pointer that is dragging the captured child view
+     */
+    public void captureChildView(View childView, int activePointerId) {
+        if (childView.getParent() != mParentView) {
+            throw new IllegalArgumentException("captureChildView: parameter must be a descendant "
+                    + "of the ViewDragHelper's tracked parent view (" + mParentView + ")");
+        }
+
+        mCapturedView = childView;
+        mActivePointerId = activePointerId;
+        mCallback.onViewCaptured(childView, activePointerId);
+        setDragState(STATE_DRAGGING);
+    }
+
+    /**
+     * @return The currently captured view, or null if no view has been captured.
+     */
+    public View getCapturedView() {
+        return mCapturedView;
+    }
+
+    /**
+     * @return The ID of the pointer currently dragging the captured view,
+     * or {@link #INVALID_POINTER}.
+     */
+    public int getActivePointerId() {
+        return mActivePointerId;
+    }
+
+    /**
+     * @return The minimum distance in pixels that the user must travel to initiate a drag
+     */
+    public int getTouchSlop() {
+        return mTouchSlop;
+    }
+
+    /**
+     * The result of a call to this method is equivalent to
+     * {@link #processTouchEvent(android.view.MotionEvent)} receiving an ACTION_CANCEL event.
+     */
+    public void cancel() {
+        mActivePointerId = INVALID_POINTER;
+        clearMotionHistory();
+
+        if (mVelocityTracker != null) {
+            mVelocityTracker.recycle();
+            mVelocityTracker = null;
+        }
+    }
+
+    /**
+     * {@link #cancel()}, but also abort all motion in progress and snap to the end of any
+     * animation.
+     */
+    public void abort() {
+        cancel();
+        if (mDragState == STATE_SETTLING) {
+            final int oldX = mScroller.getCurrX();
+            final int oldY = mScroller.getCurrY();
+            mScroller.abortAnimation();
+            final int newX = mScroller.getCurrX();
+            final int newY = mScroller.getCurrY();
+            mCallback.onViewPositionChanged(mCapturedView, newX, newY, newX - oldX, newY - oldY);
+        }
+        setDragState(STATE_IDLE);
+    }
+
+    /**
+     * Animate the view <code>child</code> to the given (left, top) position.
+     * If this method returns true, the caller should invoke {@link #continueSettling(boolean)}
+     * on each subsequent frame to continue the motion until it returns false. If this method
+     * returns false there is no further work to do to complete the movement.
+     * <p>
+     * <p>This operation does not count as a capture event, though {@link #getCapturedView()}
+     * will still report the sliding view while the slide is in progress.</p>
+     *
+     * @param child     Child view to capture and animate
+     * @param finalLeft Final left position of child
+     * @param finalTop  Final top position of child
+     * @return true if animation should continue through {@link #continueSettling(boolean)} calls
+     */
+    public boolean smoothSlideViewTo(View child, int finalLeft, int finalTop) {
+        mCapturedView = child;
+        mActivePointerId = INVALID_POINTER;
+
+        boolean continueSliding = forceSettleCapturedViewAt(finalLeft, finalTop, 0, 0);
+        if (!continueSliding && mDragState == STATE_IDLE && mCapturedView != null) {
+            // If we're in an IDLE state to begin with and aren't moving anywhere, we
+            // end up having a non-null capturedView with an IDLE dragState
+            mCapturedView = null;
+        }
+
+        return continueSliding;
+    }
+
+    /**
+     * Settle the captured view at the given (left, top) position.
+     * The appropriate velocity from prior motion will be taken into account.
+     * If this method returns true, the caller should invoke {@link #continueSettling(boolean)}
+     * on each subsequent frame to continue the motion until it returns false. If this method
+     * returns false there is no further work to do to complete the movement.
+     *
+     * @param finalLeft Settled left edge position for the captured view
+     * @param finalTop  Settled top edge position for the captured view
+     * @return true if animation should continue through {@link #continueSettling(boolean)} calls
+     */
+    public boolean settleCapturedViewAt(int finalLeft, int finalTop) {
+        if (!mReleaseInProgress) {
+            throw new IllegalStateException("Cannot settleCapturedViewAt outside of a call to "
+                    + "Callback#onViewReleased");
+        }
+
+        return forceSettleCapturedViewAt(finalLeft, finalTop,
+                (int) mVelocityTracker.getXVelocity(mActivePointerId),
+                (int) mVelocityTracker.getYVelocity(mActivePointerId));
+    }
+
+    /**
+     * Settle the captured view at the given (left, top) position.
+     *
+     * @param finalLeft Target left position for the captured view
+     * @param finalTop  Target top position for the captured view
+     * @param xvel      Horizontal velocity
+     * @param yvel      Vertical velocity
+     * @return true if animation should continue through {@link #continueSettling(boolean)} calls
+     */
+    private boolean forceSettleCapturedViewAt(int finalLeft, int finalTop, int xvel, int yvel) {
+        final int startLeft = mCapturedView.getLeft();
+        final int startTop = mCapturedView.getTop();
+        final int dx = finalLeft - startLeft;
+        final int dy = finalTop - startTop;
+
+        if (dx == 0 && dy == 0) {
+            // Nothing to do. Send callbacks, be done.
+            mScroller.abortAnimation();
+            setDragState(STATE_IDLE);
+            return false;
+        }
+
+        final int duration = computeSettleDuration(mCapturedView, dx, dy, xvel, yvel);
+        mScroller.startScroll(startLeft, startTop, dx, dy, duration);
+
+        setDragState(STATE_SETTLING);
+        return true;
+    }
+
+    private int computeSettleDuration(View child, int dx, int dy, int xvel, int yvel) {
+        xvel = clampMag(xvel, (int) mMinVelocity, (int) mMaxVelocity);
+        yvel = clampMag(yvel, (int) mMinVelocity, (int) mMaxVelocity);
+        final int absDx = Math.abs(dx);
+        final int absDy = Math.abs(dy);
+        final int absXVel = Math.abs(xvel);
+        final int absYVel = Math.abs(yvel);
+        final int addedVel = absXVel + absYVel;
+        final int addedDistance = absDx + absDy;
+
+        final float xweight = xvel != 0 ? (float) absXVel / addedVel :
+                (float) absDx / addedDistance;
+        final float yweight = yvel != 0 ? (float) absYVel / addedVel :
+                (float) absDy / addedDistance;
+
+        int xduration = computeAxisDuration(dx, xvel, mCallback.getViewHorizontalDragRange(child));
+        int yduration = computeAxisDuration(dy, yvel, mCallback.getViewVerticalDragRange(child));
+
+        return (int) (xduration * xweight + yduration * yweight);
+    }
+
+    private int computeAxisDuration(int delta, int velocity, int motionRange) {
+        if (delta == 0) {
+            return 0;
+        }
+
+        final int width = mParentView.getWidth();
+        final int halfWidth = width / 2;
+        final float distanceRatio = Math.min(1f, (float) Math.abs(delta) / width);
+        final float distance = halfWidth + halfWidth
+                * distanceInfluenceForSnapDuration(distanceRatio);
+
+        int duration;
+        velocity = Math.abs(velocity);
+        if (velocity > 0) {
+            duration = 4 * Math.round(1000 * Math.abs(distance / velocity));
+        } else {
+            final float range = (float) Math.abs(delta) / motionRange;
+            duration = (int) ((range + 1) * BASE_SETTLE_DURATION);
+        }
+        return Math.min(duration, MAX_SETTLE_DURATION);
+    }
+
+    /**
+     * Clamp the magnitude of value for absMin and absMax.
+     * If the value is below the minimum, it will be clamped to zero.
+     * If the value is above the maximum, it will be clamped to the maximum.
+     *
+     * @param value  Value to clamp
+     * @param absMin Absolute value of the minimum significant value to return
+     * @param absMax Absolute value of the maximum value to return
+     * @return The clamped value with the same sign as <code>value</code>
+     */
+    private int clampMag(int value, int absMin, int absMax) {
+        final int absValue = Math.abs(value);
+        if (absValue < absMin) return 0;
+        if (absValue > absMax) return value > 0 ? absMax : -absMax;
+        return value;
+    }
+
+    /**
+     * Clamp the magnitude of value for absMin and absMax.
+     * If the value is below the minimum, it will be clamped to zero.
+     * If the value is above the maximum, it will be clamped to the maximum.
+     *
+     * @param value  Value to clamp
+     * @param absMin Absolute value of the minimum significant value to return
+     * @param absMax Absolute value of the maximum value to return
+     * @return The clamped value with the same sign as <code>value</code>
+     */
+    private float clampMag(float value, float absMin, float absMax) {
+        final float absValue = Math.abs(value);
+        if (absValue < absMin) return 0;
+        if (absValue > absMax) return value > 0 ? absMax : -absMax;
+        return value;
+    }
+
+    private float distanceInfluenceForSnapDuration(float f) {
+        f -= 0.5f; // center the values about 0.
+        f *= 0.3f * (float) Math.PI / 2.0f;
+        return (float) Math.sin(f);
+    }
+
+    /**
+     * Settle the captured view based on standard free-moving fling behavior.
+     * The caller should invoke {@link #continueSettling(boolean)} on each subsequent frame
+     * to continue the motion until it returns false.
+     *
+     * @param minLeft Minimum X position for the view's left edge
+     * @param minTop  Minimum Y position for the view's top edge
+     * @param maxLeft Maximum X position for the view's left edge
+     * @param maxTop  Maximum Y position for the view's top edge
+     */
+    public void flingCapturedView(int minLeft, int minTop, int maxLeft, int maxTop) {
+        if (!mReleaseInProgress) {
+            throw new IllegalStateException("Cannot flingCapturedView outside of a call to "
+                    + "Callback#onViewReleased");
+        }
+
+        mScroller.fling(mCapturedView.getLeft(), mCapturedView.getTop(),
+                (int) mVelocityTracker.getXVelocity(mActivePointerId),
+                (int) mVelocityTracker.getYVelocity(mActivePointerId),
+                minLeft, maxLeft, minTop, maxTop);
+
+        setDragState(STATE_SETTLING);
+    }
+
+    /**
+     * Move the captured settling view by the appropriate amount for the current time.
+     * If <code>continueSettling</code> returns true, the caller should call it again
+     * on the next frame to continue.
+     *
+     * @param deferCallbacks true if state callbacks should be deferred via posted message.
+     *                       Set this to true if you are calling this method from
+     *                       {@link android.view.View#computeScroll()} or similar methods
+     *                       invoked as part of layout or drawing.
+     * @return true if settle is still in progress
+     */
+    public boolean continueSettling(boolean deferCallbacks) {
+        if (mDragState == STATE_SETTLING) {
+            boolean keepGoing = mScroller.computeScrollOffset();
+            final int x = mScroller.getCurrX();
+            final int y = mScroller.getCurrY();
+            final int dx = x - mCapturedView.getLeft();
+            final int dy = y - mCapturedView.getTop();
+
+            if (dx != 0) {
+                ViewCompat.offsetLeftAndRight(mCapturedView, dx);
+            }
+            if (dy != 0) {
+                ViewCompat.offsetTopAndBottom(mCapturedView, dy);
+            }
+
+            if (dx != 0 || dy != 0) {
+                mCallback.onViewPositionChanged(mCapturedView, x, y, dx, dy);
+            }
+
+            if (keepGoing && x == mScroller.getFinalX() && y == mScroller.getFinalY()) {
+                // Close enough. The interpolator/scroller might think we're still moving
+                // but the user sure doesn't.
+                mScroller.abortAnimation();
+                keepGoing = false;
+            }
+
+            if (!keepGoing) {
+                if (deferCallbacks) {
+                    mParentView.post(mSetIdleRunnable);
+                } else {
+                    setDragState(STATE_IDLE);
+                }
+            }
+        }
+
+        return mDragState == STATE_SETTLING;
+    }
+
+    /**
+     * Like all callback events this must happen on the UI thread, but release
+     * involves some extra semantics. During a release (mReleaseInProgress)
+     * is the only time it is valid to call {@link #settleCapturedViewAt(int, int)}
+     * or {@link #flingCapturedView(int, int, int, int)}.
+     */
+    private void dispatchViewReleased(float xvel, float yvel) {
+        mReleaseInProgress = true;
+        mCallback.onViewReleased(mCapturedView, xvel, yvel);
+        mReleaseInProgress = false;
+
+        if (mDragState == STATE_DRAGGING) {
+            // onViewReleased didn't call a method that would have changed this. Go idle.
+            setDragState(STATE_IDLE);
+        }
+    }
+
+    private void clearMotionHistory() {
+        if (mInitialMotionX == null) {
+            return;
+        }
+        Arrays.fill(mInitialMotionX, 0);
+        Arrays.fill(mInitialMotionY, 0);
+        Arrays.fill(mLastMotionX, 0);
+        Arrays.fill(mLastMotionY, 0);
+        Arrays.fill(mInitialEdgesTouched, 0);
+        Arrays.fill(mEdgeDragsInProgress, 0);
+        Arrays.fill(mEdgeDragsLocked, 0);
+        mPointersDown = 0;
+    }
+
+    private void clearMotionHistory(int pointerId) {
+        if (mInitialMotionX == null || !isPointerDown(pointerId)) {
+            return;
+        }
+        mInitialMotionX[pointerId] = 0;
+        mInitialMotionY[pointerId] = 0;
+        mLastMotionX[pointerId] = 0;
+        mLastMotionY[pointerId] = 0;
+        mInitialEdgesTouched[pointerId] = 0;
+        mEdgeDragsInProgress[pointerId] = 0;
+        mEdgeDragsLocked[pointerId] = 0;
+        mPointersDown &= ~(1 << pointerId);
+    }
+
+    private void ensureMotionHistorySizeForId(int pointerId) {
+        if (mInitialMotionX == null || mInitialMotionX.length <= pointerId) {
+            float[] imx = new float[pointerId + 1];
+            float[] imy = new float[pointerId + 1];
+            float[] lmx = new float[pointerId + 1];
+            float[] lmy = new float[pointerId + 1];
+            int[] iit = new int[pointerId + 1];
+            int[] edip = new int[pointerId + 1];
+            int[] edl = new int[pointerId + 1];
+
+            if (mInitialMotionX != null) {
+                System.arraycopy(mInitialMotionX, 0, imx, 0, mInitialMotionX.length);
+                System.arraycopy(mInitialMotionY, 0, imy, 0, mInitialMotionY.length);
+                System.arraycopy(mLastMotionX, 0, lmx, 0, mLastMotionX.length);
+                System.arraycopy(mLastMotionY, 0, lmy, 0, mLastMotionY.length);
+                System.arraycopy(mInitialEdgesTouched, 0, iit, 0, mInitialEdgesTouched.length);
+                System.arraycopy(mEdgeDragsInProgress, 0, edip, 0, mEdgeDragsInProgress.length);
+                System.arraycopy(mEdgeDragsLocked, 0, edl, 0, mEdgeDragsLocked.length);
+            }
+
+            mInitialMotionX = imx;
+            mInitialMotionY = imy;
+            mLastMotionX = lmx;
+            mLastMotionY = lmy;
+            mInitialEdgesTouched = iit;
+            mEdgeDragsInProgress = edip;
+            mEdgeDragsLocked = edl;
+        }
+    }
+
+    private void saveInitialMotion(float x, float y, int pointerId) {
+        ensureMotionHistorySizeForId(pointerId);
+        mInitialMotionX[pointerId] = mLastMotionX[pointerId] = x;
+        mInitialMotionY[pointerId] = mLastMotionY[pointerId] = y;
+        mInitialEdgesTouched[pointerId] = getEdgesTouched((int) x, (int) y);
+        mPointersDown |= 1 << pointerId;
+    }
+
+    private void saveLastMotion(MotionEvent ev) {
+        final int pointerCount = ev.getPointerCount();
+        for (int i = 0; i < pointerCount; i++) {
+            final int pointerId = ev.getPointerId(i);
+            // If pointer is invalid then skip saving on ACTION_MOVE.
+            if (!isValidPointerForActionMove(pointerId)) {
+                continue;
+            }
+            final float x = ev.getX(i);
+            final float y = ev.getY(i);
+            mLastMotionX[pointerId] = x;
+            mLastMotionY[pointerId] = y;
+        }
+    }
+
+    /**
+     * Check if the given pointer ID represents a pointer that is currently down (to the best
+     * of the ViewDragHelper's knowledge).
+     * <p>
+     * <p>The state used to report this information is populated by the methods
+     * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or
+     * {@link #processTouchEvent(android.view.MotionEvent)}. If one of these methods has not
+     * been called for all relevant MotionEvents to track, the information reported
+     * by this method may be stale or incorrect.</p>
+     *
+     * @param pointerId pointer ID to check; corresponds to IDs provided by MotionEvent
+     * @return true if the pointer with the given ID is still down
+     */
+    public boolean isPointerDown(int pointerId) {
+        return (mPointersDown & 1 << pointerId) != 0;
+    }
+
+    void setDragState(int state) {
+        mParentView.removeCallbacks(mSetIdleRunnable);
+        if (mDragState != state) {
+            mDragState = state;
+            mCallback.onViewDragStateChanged(state);
+            if (mDragState == STATE_IDLE) {
+                mCapturedView = null;
+            }
+        }
+    }
+
+    /**
+     * Attempt to capture the view with the given pointer ID. The callback will be involved.
+     * This will put us into the "dragging" state. If we've already captured this view with
+     * this pointer this method will immediately return true without consulting the callback.
+     *
+     * @param toCapture View to capture
+     * @param pointerId Pointer to capture with
+     * @return true if capture was successful
+     */
+    boolean tryCaptureViewForDrag(View toCapture, int pointerId) {
+        if (toCapture == mCapturedView && mActivePointerId == pointerId) {
+            // Already done!
+            return true;
+        }
+        if (toCapture != null && mCallback.tryCaptureView(toCapture, pointerId)) {
+            mActivePointerId = pointerId;
+            captureChildView(toCapture, pointerId);
+            return true;
+        }
+        return false;
+    }
+
+    /**
+     * Tests scrollability within child views of v given a delta of dx.
+     *
+     * @param v      View to test for horizontal scrollability
+     * @param checkV Whether the view v passed should itself be checked for scrollability (true),
+     *               or just its children (false).
+     * @param dx     Delta scrolled in pixels along the X axis
+     * @param dy     Delta scrolled in pixels along the Y axis
+     * @param x      X coordinate of the active touch point
+     * @param y      Y coordinate of the active touch point
+     * @return true if child views of v can be scrolled by delta of dx.
+     */
+    protected boolean canScroll(View v, boolean checkV, int dx, int dy, int x, int y) {
+        if (v instanceof ViewGroup) {
+            final ViewGroup group = (ViewGroup) v;
+            final int scrollX = v.getScrollX();
+            final int scrollY = v.getScrollY();
+            final int count = group.getChildCount();
+            // Count backwards - let topmost views consume scroll distance first.
+            for (int i = count - 1; i >= 0; i--) {
+                // TODO: Add versioned support here for transformed views.
+                // This will not work for transformed views in Honeycomb+
+                final View child = group.getChildAt(i);
+                if (x + scrollX >= child.getLeft() && x + scrollX < child.getRight()
+                        && y + scrollY >= child.getTop() && y + scrollY < child.getBottom()
+                        && canScroll(child, true, dx, dy, x + scrollX - child.getLeft(),
+                        y + scrollY - child.getTop())) {
+                    return true;
+                }
+            }
+        }
+
+        return checkV && (v.canScrollHorizontally(-dx) || v.canScrollVertically(-dy));
+    }
+
+    /**
+     * Check if this event as provided to the parent view's onInterceptTouchEvent should
+     * cause the parent to intercept the touch event stream.
+     *
+     * @param ev MotionEvent provided to onInterceptTouchEvent
+     * @return true if the parent view should return true from onInterceptTouchEvent
+     */
+    public boolean shouldInterceptTouchEvent(MotionEvent ev) {
+        final int action = ev.getActionMasked();
+        final int actionIndex = ev.getActionIndex();
+
+        if (action == MotionEvent.ACTION_DOWN) {
+            // Reset things for a new event stream, just in case we didn't get
+            // the whole previous stream.
+            cancel();
+        }
+
+        if (mVelocityTracker == null) {
+            mVelocityTracker = VelocityTracker.obtain();
+        }
+        mVelocityTracker.addMovement(ev);
+
+        switch (action) {
+            case MotionEvent.ACTION_DOWN: {
+                final float x = ev.getX();
+                final float y = ev.getY();
+                final int pointerId = ev.getPointerId(0);
+                saveInitialMotion(x, y, pointerId);
+
+                final View toCapture = findTopChildUnder((int) x, (int) y);
+
+                // Catch a settling view if possible.
+                if (toCapture == mCapturedView && mDragState == STATE_SETTLING) {
+                    tryCaptureViewForDrag(toCapture, pointerId);
+                }
+
+                final int edgesTouched = mInitialEdgesTouched[pointerId];
+                if ((edgesTouched & mTrackingEdges) != 0) {
+                    mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);
+                }
+                break;
+            }
+
+            case MotionEvent.ACTION_POINTER_DOWN: {
+                final int pointerId = ev.getPointerId(actionIndex);
+                final float x = ev.getX(actionIndex);
+                final float y = ev.getY(actionIndex);
+
+                saveInitialMotion(x, y, pointerId);
+
+                // A ViewDragHelper can only manipulate one view at a time.
+                if (mDragState == STATE_IDLE) {
+                    final int edgesTouched = mInitialEdgesTouched[pointerId];
+                    if ((edgesTouched & mTrackingEdges) != 0) {
+                        mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);
+                    }
+                } else if (mDragState == STATE_SETTLING) {
+                    // Catch a settling view if possible.
+                    final View toCapture = findTopChildUnder((int) x, (int) y);
+                    if (toCapture == mCapturedView) {
+                        tryCaptureViewForDrag(toCapture, pointerId);
+                    }
+                }
+                break;
+            }
+
+            case MotionEvent.ACTION_MOVE: {
+                if (mInitialMotionX == null || mInitialMotionY == null) break;
+
+                // First to cross a touch slop over a draggable view wins. Also report edge drags.
+                final int pointerCount = ev.getPointerCount();
+                for (int i = 0; i < pointerCount; i++) {
+                    final int pointerId = ev.getPointerId(i);
+
+                    // If pointer is invalid then skip the ACTION_MOVE.
+                    if (!isValidPointerForActionMove(pointerId)) continue;
+
+                    final float x = ev.getX(i);
+                    final float y = ev.getY(i);
+                    final float dx = x - mInitialMotionX[pointerId];
+                    final float dy = y - mInitialMotionY[pointerId];
+
+                    final View toCapture = findTopChildUnder((int) x, (int) y);
+                    final boolean pastSlop = toCapture != null && checkTouchSlop(toCapture, dx, dy);
+                    if (pastSlop) {
+                        // check the callback's
+                        // getView[Horizontal|Vertical]DragRange methods to know
+                        // if you can move at all along an axis, then see if it
+                        // would clamp to the same value. If you can't move at
+                        // all in every dimension with a nonzero range, bail.
+                        final int oldLeft = toCapture.getLeft();
+                        final int targetLeft = oldLeft + (int) dx;
+                        final int newLeft = mCallback.clampViewPositionHorizontal(toCapture,
+                                targetLeft, (int) dx);
+                        final int oldTop = toCapture.getTop();
+                        final int targetTop = oldTop + (int) dy;
+                        final int newTop = mCallback.clampViewPositionVertical(toCapture, targetTop,
+                                (int) dy);
+                        final int hDragRange = mCallback.getViewHorizontalDragRange(toCapture);
+                        final int vDragRange = mCallback.getViewVerticalDragRange(toCapture);
+                        if ((hDragRange == 0 || (hDragRange > 0 && newLeft == oldLeft))
+                                && (vDragRange == 0 || (vDragRange > 0 && newTop == oldTop))) {
+                            break;
+                        }
+                    }
+                    reportNewEdgeDrags(dx, dy, pointerId);
+                    if (mDragState == STATE_DRAGGING) {
+                        // Callback might have started an edge drag
+                        break;
+                    }
+
+                    if (pastSlop && tryCaptureViewForDrag(toCapture, pointerId)) {
+                        break;
+                    }
+                }
+                saveLastMotion(ev);
+                break;
+            }
+
+            case MotionEvent.ACTION_POINTER_UP: {
+                final int pointerId = ev.getPointerId(actionIndex);
+                clearMotionHistory(pointerId);
+                break;
+            }
+
+            case MotionEvent.ACTION_UP:
+            case MotionEvent.ACTION_CANCEL: {
+                cancel();
+                break;
+            }
+        }
+
+        return mDragState == STATE_DRAGGING;
+    }
+
+    /**
+     * Process a touch event received by the parent view. This method will dispatch callback events
+     * as needed before returning. The parent view's onTouchEvent implementation should call this.
+     *
+     * @param ev The touch event received by the parent view
+     */
+    public void processTouchEvent(MotionEvent ev) {
+        final int action = ev.getActionMasked();
+        final int actionIndex = ev.getActionIndex();
+
+        if (action == MotionEvent.ACTION_DOWN) {
+            // Reset things for a new event stream, just in case we didn't get
+            // the whole previous stream.
+            cancel();
+        }
+
+        if (mVelocityTracker == null) {
+            mVelocityTracker = VelocityTracker.obtain();
+        }
+        mVelocityTracker.addMovement(ev);
+
+        switch (action) {
+            case MotionEvent.ACTION_DOWN: {
+                final float x = ev.getX();
+                final float y = ev.getY();
+                final int pointerId = ev.getPointerId(0);
+                final View toCapture = findTopChildUnder((int) x, (int) y);
+
+                saveInitialMotion(x, y, pointerId);
+
+                // Since the parent is already directly processing this touch event,
+                // there is no reason to delay for a slop before dragging.
+                // Start immediately if possible.
+                tryCaptureViewForDrag(toCapture, pointerId);
+
+                final int edgesTouched = mInitialEdgesTouched[pointerId];
+                if ((edgesTouched & mTrackingEdges) != 0) {
+                    mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);
+                }
+                break;
+            }
+
+            case MotionEvent.ACTION_POINTER_DOWN: {
+                final int pointerId = ev.getPointerId(actionIndex);
+                final float x = ev.getX(actionIndex);
+                final float y = ev.getY(actionIndex);
+
+                saveInitialMotion(x, y, pointerId);
+
+                // A ViewDragHelper can only manipulate one view at a time.
+                if (mDragState == STATE_IDLE) {
+                    // If we're idle we can do anything! Treat it like a normal down event.
+
+                    final View toCapture = findTopChildUnder((int) x, (int) y);
+                    tryCaptureViewForDrag(toCapture, pointerId);
+
+                    final int edgesTouched = mInitialEdgesTouched[pointerId];
+                    if ((edgesTouched & mTrackingEdges) != 0) {
+                        mCallback.onEdgeTouched(edgesTouched & mTrackingEdges, pointerId);
+                    }
+                } else if (isCapturedViewUnder((int) x, (int) y)) {
+                    // We're still tracking a captured view. If the same view is under this
+                    // point, we'll swap to controlling it with this pointer instead.
+                    // (This will still work if we're "catching" a settling view.)
+
+                    tryCaptureViewForDrag(mCapturedView, pointerId);
+                }
+                break;
+            }
+
+            case MotionEvent.ACTION_MOVE: {
+                if (mDragState == STATE_DRAGGING) {
+                    // If pointer is invalid then skip the ACTION_MOVE.
+                    if (!isValidPointerForActionMove(mActivePointerId)) break;
+
+                    final int index = ev.findPointerIndex(mActivePointerId);
+                    final float x = ev.getX(index);
+                    final float y = ev.getY(index);
+                    final int idx = (int) (x - mLastMotionX[mActivePointerId]);
+                    final int idy = (int) (y - mLastMotionY[mActivePointerId]);
+
+                    dragTo(mCapturedView.getLeft() + idx, mCapturedView.getTop() + idy, idx, idy);
+
+                    saveLastMotion(ev);
+                } else {
+                    // Check to see if any pointer is now over a draggable view.
+                    final int pointerCount = ev.getPointerCount();
+                    for (int i = 0; i < pointerCount; i++) {
+                        final int pointerId = ev.getPointerId(i);
+
+                        // If pointer is invalid then skip the ACTION_MOVE.
+                        if (!isValidPointerForActionMove(pointerId)) continue;
+
+                        final float x = ev.getX(i);
+                        final float y = ev.getY(i);
+                        final float dx = x - mInitialMotionX[pointerId];
+                        final float dy = y - mInitialMotionY[pointerId];
+
+                        reportNewEdgeDrags(dx, dy, pointerId);
+                        if (mDragState == STATE_DRAGGING) {
+                            // Callback might have started an edge drag.
+                            break;
+                        }
+
+                        final View toCapture = findTopChildUnder((int) x, (int) y);
+                        if (checkTouchSlop(toCapture, dx, dy)
+                                && tryCaptureViewForDrag(toCapture, pointerId)) {
+                            break;
+                        }
+                    }
+                    saveLastMotion(ev);
+                }
+                break;
+            }
+
+            case MotionEvent.ACTION_POINTER_UP: {
+                final int pointerId = ev.getPointerId(actionIndex);
+                if (mDragState == STATE_DRAGGING && pointerId == mActivePointerId) {
+                    // Try to find another pointer that's still holding on to the captured view.
+                    int newActivePointer = INVALID_POINTER;
+                    final int pointerCount = ev.getPointerCount();
+                    for (int i = 0; i < pointerCount; i++) {
+                        final int id = ev.getPointerId(i);
+                        if (id == mActivePointerId) {
+                            // This one's going away, skip.
+                            continue;
+                        }
+
+                        final float x = ev.getX(i);
+                        final float y = ev.getY(i);
+                        if (findTopChildUnder((int) x, (int) y) == mCapturedView
+                                && tryCaptureViewForDrag(mCapturedView, id)) {
+                            newActivePointer = mActivePointerId;
+                            break;
+                        }
+                    }
+
+                    if (newActivePointer == INVALID_POINTER) {
+                        // We didn't find another pointer still touching the view, release it.
+                        releaseViewForPointerUp();
+                    }
+                }
+                clearMotionHistory(pointerId);
+                break;
+            }
+
+            case MotionEvent.ACTION_UP: {
+                if (mDragState == STATE_DRAGGING) {
+                    releaseViewForPointerUp();
+                }
+                cancel();
+                break;
+            }
+
+            case MotionEvent.ACTION_CANCEL: {
+                if (mDragState == STATE_DRAGGING) {
+                    dispatchViewReleased(0, 0);
+                }
+                cancel();
+                break;
+            }
+        }
+    }
+
+    private void reportNewEdgeDrags(float dx, float dy, int pointerId) {
+        int dragsStarted = 0;
+        if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_LEFT)) {
+            dragsStarted |= EDGE_LEFT;
+        }
+        if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_TOP)) {
+            dragsStarted |= EDGE_TOP;
+        }
+        if (checkNewEdgeDrag(dx, dy, pointerId, EDGE_RIGHT)) {
+            dragsStarted |= EDGE_RIGHT;
+        }
+        if (checkNewEdgeDrag(dy, dx, pointerId, EDGE_BOTTOM)) {
+            dragsStarted |= EDGE_BOTTOM;
+        }
+
+        if (dragsStarted != 0) {
+            mEdgeDragsInProgress[pointerId] |= dragsStarted;
+            mCallback.onEdgeDragStarted(dragsStarted, pointerId);
+        }
+    }
+
+    private boolean checkNewEdgeDrag(float delta, float odelta, int pointerId, int edge) {
+        final float absDelta = Math.abs(delta);
+        final float absODelta = Math.abs(odelta);
+
+        if ((mInitialEdgesTouched[pointerId] & edge) != edge || (mTrackingEdges & edge) == 0
+                || (mEdgeDragsLocked[pointerId] & edge) == edge
+                || (mEdgeDragsInProgress[pointerId] & edge) == edge
+                || (absDelta <= mTouchSlop && absODelta <= mTouchSlop)) {
+            return false;
+        }
+        if (absDelta < absODelta * 0.5f && mCallback.onEdgeLock(edge)) {
+            mEdgeDragsLocked[pointerId] |= edge;
+            return false;
+        }
+        return (mEdgeDragsInProgress[pointerId] & edge) == 0 && absDelta > mTouchSlop;
+    }
+
+    /**
+     * Check if we've crossed a reasonable touch slop for the given child view.
+     * If the child cannot be dragged along the horizontal or vertical axis, motion
+     * along that axis will not count toward the slop check.
+     *
+     * @param child Child to check
+     * @param dx    Motion since initial position along X axis
+     * @param dy    Motion since initial position along Y axis
+     * @return true if the touch slop has been crossed
+     */
+    private boolean checkTouchSlop(View child, float dx, float dy) {
+        if (child == null) {
+            return false;
+        }
+        final boolean checkHorizontal = mCallback.getViewHorizontalDragRange(child) > 0;
+        final boolean checkVertical = mCallback.getViewVerticalDragRange(child) > 0;
+
+        if (checkHorizontal && checkVertical) {
+            return dx * dx + dy * dy > mTouchSlop * mTouchSlop;
+        } else if (checkHorizontal) {
+            return Math.abs(dx) > mTouchSlop;
+        } else if (checkVertical) {
+            return Math.abs(dy) > mTouchSlop;
+        }
+        return false;
+    }
+
+    /**
+     * Check if any pointer tracked in the current gesture has crossed
+     * the required slop threshold.
+     * <p>
+     * <p>This depends on internal state populated by
+     * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or
+     * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on
+     * the results of this method after all currently available touch data
+     * has been provided to one of these two methods.</p>
+     *
+     * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL},
+     *                   {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL}
+     * @return true if the slop threshold has been crossed, false otherwise
+     */
+    public boolean checkTouchSlop(int directions) {
+        final int count = mInitialMotionX.length;
+        for (int i = 0; i < count; i++) {
+            if (checkTouchSlop(directions, i)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Check if the specified pointer tracked in the current gesture has crossed
+     * the required slop threshold.
+     * <p>
+     * <p>This depends on internal state populated by
+     * {@link #shouldInterceptTouchEvent(android.view.MotionEvent)} or
+     * {@link #processTouchEvent(android.view.MotionEvent)}. You should only rely on
+     * the results of this method after all currently available touch data
+     * has been provided to one of these two methods.</p>
+     *
+     * @param directions Combination of direction flags, see {@link #DIRECTION_HORIZONTAL},
+     *                   {@link #DIRECTION_VERTICAL}, {@link #DIRECTION_ALL}
+     * @param pointerId  ID of the pointer to slop check as specified by MotionEvent
+     * @return true if the slop threshold has been crossed, false otherwise
+     */
+    public boolean checkTouchSlop(int directions, int pointerId) {
+        if (!isPointerDown(pointerId)) {
+            return false;
+        }
+
+        final boolean checkHorizontal = (directions & DIRECTION_HORIZONTAL) == DIRECTION_HORIZONTAL;
+        final boolean checkVertical = (directions & DIRECTION_VERTICAL) == DIRECTION_VERTICAL;
+
+        final float dx = mLastMotionX[pointerId] - mInitialMotionX[pointerId];
+        final float dy = mLastMotionY[pointerId] - mInitialMotionY[pointerId];
+
+        if (checkHorizontal && checkVertical) {
+            return dx * dx + dy * dy > mTouchSlop * mTouchSlop;
+        } else if (checkHorizontal) {
+            return Math.abs(dx) > mTouchSlop;
+        } else if (checkVertical) {
+            return Math.abs(dy) > mTouchSlop;
+        }
+        return false;
+    }
+
+    /**
+     * Check if any of the edges specified were initially touched in the currently active gesture.
+     * If there is no currently active gesture this method will return false.
+     *
+     * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT},
+     *              {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and
+     *              {@link #EDGE_ALL}
+     * @return true if any of the edges specified were initially touched in the current gesture
+     */
+    public boolean isEdgeTouched(int edges) {
+        final int count = mInitialEdgesTouched.length;
+        for (int i = 0; i < count; i++) {
+            if (isEdgeTouched(edges, i)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Check if any of the edges specified were initially touched by the pointer with
+     * the specified ID. If there is no currently active gesture or if there is no pointer with
+     * the given ID currently down this method will return false.
+     *
+     * @param edges Edges to check for an initial edge touch. See {@link #EDGE_LEFT},
+     *              {@link #EDGE_TOP}, {@link #EDGE_RIGHT}, {@link #EDGE_BOTTOM} and
+     *              {@link #EDGE_ALL}
+     * @return true if any of the edges specified were initially touched in the current gesture
+     */
+    public boolean isEdgeTouched(int edges, int pointerId) {
+        return isPointerDown(pointerId) && (mInitialEdgesTouched[pointerId] & edges) != 0;
+    }
+
+    private void releaseViewForPointerUp() {
+        mVelocityTracker.computeCurrentVelocity(1000, mMaxVelocity);
+        final float xvel = clampMag(
+                mVelocityTracker.getXVelocity(mActivePointerId),
+                mMinVelocity, mMaxVelocity);
+        final float yvel = clampMag(
+                mVelocityTracker.getYVelocity(mActivePointerId),
+                mMinVelocity, mMaxVelocity);
+        dispatchViewReleased(xvel, yvel);
+    }
+
+    private void dragTo(int left, int top, int dx, int dy) {
+        int clampedX = left;
+        int clampedY = top;
+        final int oldLeft = mCapturedView.getLeft();
+        final int oldTop = mCapturedView.getTop();
+        if (dx != 0) {
+            clampedX = mCallback.clampViewPositionHorizontal(mCapturedView, left, dx);
+            ViewCompat.offsetLeftAndRight(mCapturedView, clampedX - oldLeft);
+        }
+        if (dy != 0) {
+            clampedY = mCallback.clampViewPositionVertical(mCapturedView, top, dy);
+            ViewCompat.offsetTopAndBottom(mCapturedView, clampedY - oldTop);
+        }
+
+        if (dx != 0 || dy != 0) {
+            final int clampedDx = clampedX - oldLeft;
+            final int clampedDy = clampedY - oldTop;
+            mCallback.onViewPositionChanged(mCapturedView, clampedX, clampedY,
+                    clampedDx, clampedDy);
+        }
+    }
+
+    /**
+     * Determine if the currently captured view is under the given point in the
+     * parent view's coordinate system. If there is no captured view this method
+     * will return false.
+     *
+     * @param x X position to test in the parent's coordinate system
+     * @param y Y position to test in the parent's coordinate system
+     * @return true if the captured view is under the given point, false otherwise
+     */
+    public boolean isCapturedViewUnder(int x, int y) {
+        return isViewUnder(mCapturedView, x, y);
+    }
+
+    /**
+     * Determine if the supplied view is under the given point in the
+     * parent view's coordinate system.
+     *
+     * @param view Child view of the parent to hit test
+     * @param x    X position to test in the parent's coordinate system
+     * @param y    Y position to test in the parent's coordinate system
+     * @return true if the supplied view is under the given point, false otherwise
+     */
+    public boolean isViewUnder(View view, int x, int y) {
+        if (view == null) {
+            return false;
+        }
+        return x >= view.getLeft()
+                && x < view.getRight()
+                && y >= view.getTop()
+                && y < view.getBottom();
+    }
+
+    /**
+     * Find the topmost child under the given point within the parent view's coordinate system.
+     * The child order is determined using {@link ViewDragHelper.Callback#getOrderedChildIndex(int)}.
+     *
+     * @param x X position to test in the parent's coordinate system
+     * @param y Y position to test in the parent's coordinate system
+     * @return The topmost child view under (x, y) or null if none found.
+     */
+    public View findTopChildUnder(int x, int y) {
+        final int childCount = mParentView.getChildCount();
+        for (int i = childCount - 1; i >= 0; i--) {
+            final View child = mParentView.getChildAt(mCallback.getOrderedChildIndex(i));
+            if (x >= child.getLeft() && x < child.getRight()
+                    && y >= child.getTop() && y < child.getBottom()) {
+                return child;
+            }
+        }
+        return null;
+    }
+
+    private int getEdgesTouched(int x, int y) {
+        int result = 0;
+
+        if (x < mParentView.getLeft() + mEdgeSize) result |= EDGE_LEFT;
+        if (y < mParentView.getTop() + mEdgeSize) result |= EDGE_TOP;
+        if (x > mParentView.getRight() - mEdgeSize) result |= EDGE_RIGHT;
+        if (y > mParentView.getBottom() - mEdgeSize) result |= EDGE_BOTTOM;
+
+        return result;
+    }
+
+    private boolean isValidPointerForActionMove(int pointerId) {
+        if (!isPointerDown(pointerId)) {
+            Log.e(TAG, "Ignoring pointerId=" + pointerId + " because ACTION_DOWN was not received "
+                    + "for this pointer before ACTION_MOVE. It likely happened because "
+                    + " ViewDragHelper did not receive all the events in the event stream.");
+            return false;
+        }
+        return true;
+    }
+}