From 75222c4321d5d2c51b49f82fcc9212994c6ace99 Mon Sep 17 00:00:00 2001
From: Scott Jackson <daneren2005@gmail.com>
Date: Mon, 26 Oct 2015 17:14:23 -0700
Subject: More work on smooth scrolling + getting it to work on grid managers

---
 .../github/daneren2005/dsub/view/FastScroller.java | 75 +++++++++++++++++++++-
 1 file changed, 72 insertions(+), 3 deletions(-)

(limited to 'app/src')

diff --git a/app/src/main/java/github/daneren2005/dsub/view/FastScroller.java b/app/src/main/java/github/daneren2005/dsub/view/FastScroller.java
index bdfde1cf..ba83e46c 100644
--- a/app/src/main/java/github/daneren2005/dsub/view/FastScroller.java
+++ b/app/src/main/java/github/daneren2005/dsub/view/FastScroller.java
@@ -23,6 +23,7 @@ import android.content.Context;
 import android.support.annotation.NonNull;
 import android.support.v7.widget.LinearLayoutManager;
 import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.AdapterDataObserver;
 import android.util.AttributeSet;
 import android.util.Log;
 import android.view.LayoutInflater;
@@ -45,6 +46,9 @@ public class FastScroller extends LinearLayout {
 	private RecyclerView recyclerView;
 	private final ScrollListener scrollListener = new ScrollListener();
 	private int height;
+	private int visibleRange = -1;
+	private RecyclerView.Adapter adapter;
+	private AdapterDataObserver adapterObserver;
 	private boolean visibleBubble = true;
 	private boolean hasScrolled = false;
 
@@ -80,6 +84,7 @@ public class FastScroller extends LinearLayout {
 	protected void onSizeChanged(int w,int h,int oldw,int oldh) {
 		super.onSizeChanged(w,h,oldw,oldh);
 		height = h;
+		visibleRange = -1;
 	}
 
 	@Override
@@ -121,10 +126,13 @@ public class FastScroller extends LinearLayout {
 	public void attachRecyclerView(RecyclerView recyclerView) {
 		this.recyclerView = recyclerView;
 		recyclerView.addOnScrollListener(scrollListener);
+		registerAdapter();
+		visibleRange = -1;
 	}
 	public void detachRecyclerView() {
 		recyclerView.removeOnScrollListener(scrollListener);
 		recyclerView.setVerticalScrollBarEnabled(true);
+		unregisterAdapter();
 		recyclerView = null;
 		setVisibility(View.GONE);
 	}
@@ -147,7 +155,12 @@ public class FastScroller extends LinearLayout {
 			((LinearLayoutManager)recyclerView.getLayoutManager()).scrollToPositionWithOffset(targetPos,0);
 
 			try {
-				String bubbleText = ((BubbleTextGetter) recyclerView.getAdapter()).getTextToShowInBubble(targetPos);
+				String bubbleText = null;
+				RecyclerView.Adapter adapter = recyclerView.getAdapter();
+				if(adapter instanceof BubbleTextGetter) {
+					bubbleText = ((BubbleTextGetter) adapter).getTextToShowInBubble(targetPos);
+				}
+
 				if(bubbleText == null) {
 					visibleBubble = false;
 					bubble.setVisibility(View.INVISIBLE);
@@ -203,16 +216,72 @@ public class FastScroller extends LinearLayout {
 		currentAnimator.start();
 	}
 
+	private void registerAdapter() {
+		RecyclerView.Adapter newAdapter = recyclerView.getAdapter();
+		if(newAdapter != adapter) {
+			unregisterAdapter();
+		}
+
+		if(newAdapter != null) {
+			adapterObserver = new AdapterDataObserver() {
+				@Override
+				public void onChanged() {
+					visibleRange = -1;
+				}
+
+				@Override
+				public void onItemRangeChanged(int positionStart, int itemCount) {
+					visibleRange = -1;
+				}
+
+				@Override
+				public void onItemRangeInserted(int positionStart, int itemCount) {
+					visibleRange = -1;
+				}
+
+				@Override
+				public void onItemRangeMoved(int fromPosition, int toPosition, int itemCount) {
+					visibleRange = -1;
+				}
+
+				@Override
+				public void onItemRangeRemoved(int positionStart, int itemCount) {
+					visibleRange = -1;
+				}
+			};
+			newAdapter.registerAdapterDataObserver(adapterObserver);
+			adapter = newAdapter;
+		}
+	}
+	private void unregisterAdapter() {
+		if(adapter != null) {
+			adapter.unregisterAdapterDataObserver(adapterObserver);
+			adapter = null;
+			adapterObserver = null;
+		}
+	}
+
 	private class ScrollListener extends OnScrollListener {
 		@Override
 		public void onScrolled(RecyclerView rv,int dx,int dy) {
+			registerAdapter();
+
 			View firstVisibleView = recyclerView.getChildAt(0);
 			int firstVisiblePosition = recyclerView.getChildPosition(firstVisibleView);
-			int visibleRange = recyclerView.getChildCount();
+			if(visibleRange == -1) {
+				visibleRange = recyclerView.getChildCount();
+			}
 			int itemCount = recyclerView.getAdapter().getItemCount();
+			int columns = Math.round(recyclerView.getWidth() / firstVisibleView.getWidth());
 
 			// Add the percentage of the item the user has scrolled past already
-			float position = firstVisiblePosition + (-firstVisibleView.getY() / firstVisibleView.getHeight());
+			float pastFirst = -firstVisibleView.getY() / firstVisibleView.getHeight() * columns;
+			float position = firstVisiblePosition + pastFirst;
+
+			// Scale this so as we move down the visible range gets added to position from 0 -> visible range
+			float scaledVisibleRange = position / (float) (itemCount - visibleRange) * visibleRange;
+			position += scaledVisibleRange;
+
 			float proportion = position / itemCount;
 			setBubbleAndHandlePosition(height * proportion);
 
-- 
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