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Diffstat (limited to 'adapter/src/main/kotlin/ca/allanwang/kau/adapters/ChainedAdapters.kt')
| -rw-r--r-- | adapter/src/main/kotlin/ca/allanwang/kau/adapters/ChainedAdapters.kt | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/adapter/src/main/kotlin/ca/allanwang/kau/adapters/ChainedAdapters.kt b/adapter/src/main/kotlin/ca/allanwang/kau/adapters/ChainedAdapters.kt new file mode 100644 index 0000000..e1c5c18 --- /dev/null +++ b/adapter/src/main/kotlin/ca/allanwang/kau/adapters/ChainedAdapters.kt @@ -0,0 +1,85 @@ +package ca.allanwang.kau.adapters + +import android.support.v7.widget.LinearLayoutManager +import android.support.v7.widget.RecyclerView +import com.mikepenz.fastadapter.IItem +import com.mikepenz.fastadapter.adapters.HeaderAdapter +import com.mikepenz.fastadapter.commons.adapters.FastItemAdapter +import org.jetbrains.anko.collections.forEachReversedWithIndex +import java.util.* + +/** + * Created by Allan Wang on 2017-06-27. + * + * Once bounded to a [RecyclerView], this will + * - Chain together a list of [HeaderAdapter]s, backed by a generic [FastItemAdapter] + * - Add a [LinearLayoutManager] to the recycler + * - Add a listener for when a new adapter segment is being used + */ +class ChainedAdapters<T>(vararg items: Pair<T, SectionAdapter<*>>) { + private val chain: MutableList<Pair<T, SectionAdapter<*>>> = mutableListOf(*items) + val baseAdapter: FastItemAdapter<IItem<*, *>> = FastItemAdapter() + private val indexStack = Stack<Int>() + var recycler: RecyclerView? = null + val firstVisibleItemPosition: Int + get() = (recycler?.layoutManager as LinearLayoutManager?)?.findFirstVisibleItemPosition() ?: throw IllegalArgumentException("No recyclerview was bounded to the chain adapters") + + fun add(vararg items: Pair<T, SectionAdapter<*>>) = add(items.toList()) + + fun add(items: Collection<Pair<T, SectionAdapter<*>>>): ChainedAdapters<T> { + if (recycler != null) throw IllegalAccessException("Chain adapter is already bounded to a recycler; cannot add directly.") + items.map { it.second }.forEachIndexed { index, sectionAdapter -> sectionAdapter.sectionOrder = chain.size + 1 + index } + chain.addAll(items) + return this + } + + operator fun get(index: Int) = chain[index] + + /** + * Attaches the chain to a recycler + * After this stage, any modifications to the adapters must be done through external references + * You may still get the generic header adapters through the get operator + * Binding the recycler also involves supplying a callback, which returns + * the item (T) associated with the adapter, + * the index (Int) of the current adapter + * and the dy (Int) as given by the scroll listener + */ + fun bindRecyclerView(recyclerView: RecyclerView, onAdapterSectionChanged: (item: T, index: Int, dy: Int) -> Unit) { + if (recycler != null) throw IllegalStateException("Chain adapter is already bounded") + if (chain.isEmpty()) throw IllegalArgumentException("No adapters have been added to the adapters list") + //wrap adapters + chain.map { it.second }.forEachReversedWithIndex { i, headerAdapter -> + if (i == chain.size - 1) headerAdapter.wrap(baseAdapter) + else headerAdapter.wrap(chain[i + 1].second) + } + recycler = recyclerView + indexStack.push(0) + with(recyclerView) { + layoutManager = LinearLayoutManager(context) + adapter = chain.first().second + addOnScrollListener(object : RecyclerView.OnScrollListener() { + override fun onScrolled(rv: RecyclerView, dx: Int, dy: Int) { + super.onScrolled(rv, dx, dy) + val topPosition = firstVisibleItemPosition + val currentAdapterIndex = indexStack.peek() + if (dy > 0) { + //look ahead from current adapter + val nextAdapterIndex = (currentAdapterIndex until chain.size).asSequence() + .firstOrNull { + val adapter = chain[it].second + adapter.adapterItemCount > 0 && adapter.getGlobalPosition(adapter.adapterItemCount - 1) >= topPosition + } ?: currentAdapterIndex + if (nextAdapterIndex == currentAdapterIndex) return + indexStack.push(nextAdapterIndex) + onAdapterSectionChanged(chain[indexStack.peek()].first, indexStack.peek(), dy) + } else if (currentAdapterIndex == 0) { + return //All adapters may be empty; in this case, if we are already at the beginning, don't bother checking + } else if (chain[currentAdapterIndex].second.getGlobalPosition(0) > topPosition) { + indexStack.pop() + onAdapterSectionChanged(chain[indexStack.peek()].first, indexStack.peek(), dy) + } + } + }) + } + } +}
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