Invalidate item decorations automatically when adapter contents change

dpadrecyclerview/api/dpadrecyclerview.api

@@ -138,6 +138,7 @@ public class com/rubensousa/dpadrecyclerview/DpadRecyclerView : androidx/recycle
 	public final fun removeView (Landroid/view/View;)V
 	public final fun removeViewAt (I)V
 	public final fun requestLayout ()V
+	public fun setAdapter (Landroidx/recyclerview/widget/RecyclerView$Adapter;)V
 	public final fun setAlignmentLookup (Lcom/rubensousa/dpadrecyclerview/AlignmentLookup;Z)V
 	public static synthetic fun setAlignmentLookup$default (Lcom/rubensousa/dpadrecyclerview/DpadRecyclerView;Lcom/rubensousa/dpadrecyclerview/AlignmentLookup;ZILjava/lang/Object;)V
 	public final fun setAlignments (Lcom/rubensousa/dpadrecyclerview/ParentAlignment;Lcom/rubensousa/dpadrecyclerview/ChildAlignment;Z)V

dpadrecyclerview/src/androidTest/kotlin/com/rubensousa/dpadrecyclerview/test/tests/AbstractTestAdapter.kt

@@ -27,7 +27,7 @@ import java.util.Collections
 import java.util.concurrent.Executors
 
 abstract class AbstractTestAdapter<VH : RecyclerView.ViewHolder>(
-    adapterConfiguration: TestAdapterConfiguration
+    adapterConfiguration: TestAdapterConfiguration,
 ) : RecyclerView.Adapter<VH>(), DpadDragHelper.DragAdapter<Int> {
 
     companion object {
@@ -84,7 +84,7 @@ abstract class AbstractTestAdapter<VH : RecyclerView.ViewHolder>(
 
     private fun calculateDiff(
         oldList: List<Int>,
-        newList: List<Int>
+        newList: List<Int>,
     ): DiffResult {
         return DiffUtil.calculateDiff(object : DiffUtil.Callback() {
             override fun getOldListSize(): Int = oldList.size
@@ -98,7 +98,7 @@ abstract class AbstractTestAdapter<VH : RecyclerView.ViewHolder>(
 
             override fun areContentsTheSame(
                 oldItemPosition: Int,
-                newItemPosition: Int
+                newItemPosition: Int,
             ): Boolean {
                 val oldItem = oldList[oldItemPosition]
                 val newItem = newList[newItemPosition]
@@ -110,7 +110,7 @@ abstract class AbstractTestAdapter<VH : RecyclerView.ViewHolder>(
     private fun latchList(
         newList: MutableList<Int>,
         result: DiffResult,
-        commitCallback: Runnable?
+        commitCallback: Runnable?,
     ) {
         items = newList
         result.dispatchUpdatesTo(this)
@@ -123,13 +123,22 @@ abstract class AbstractTestAdapter<VH : RecyclerView.ViewHolder>(
         notifyItemRemoved(index)
     }
 
+    fun removeFrom(index: Int, count: Int) {
+        currentVersion++
+        repeat(count) {
+            items.removeAt(index)
+        }
+        notifyItemRangeRemoved(index, count)
+    }
+
+
     fun move(from: Int, to: Int) {
         currentVersion++
         Collections.swap(items, from, to)
         notifyItemMoved(from, to)
     }
 
-    fun addAt(item: Int, index: Int) {
+    fun addAt(index: Int, item: Int) {
         currentVersion++
         items.add(index, item)
         notifyItemInserted(index)

dpadrecyclerview/src/androidTest/kotlin/com/rubensousa/dpadrecyclerview/test/tests/focus/VerticalFocusTest.kt

@@ -169,7 +169,7 @@ class VerticalFocusTest : DpadRecyclerViewTest() {
             recyclerView.itemAnimator?.moveDuration = 2500L
         }
         mutateAdapter { adapter ->
-            adapter.addAt(1000, index = 3)
+            adapter.addAt(item = 1000, index = 3)
         }
         waitForCondition("Waiting for animation start") { recyclerView ->
             recyclerView.isAnimating

dpadrecyclerview/src/androidTest/kotlin/com/rubensousa/dpadrecyclerview/test/tests/mutation/AdapterMutationTest.kt

@@ -22,10 +22,13 @@ import androidx.test.platform.app.InstrumentationRegistry
 import com.google.common.truth.Truth.assertThat
 import com.rubensousa.dpadrecyclerview.ChildAlignment
 import com.rubensousa.dpadrecyclerview.ParentAlignment
+import com.rubensousa.dpadrecyclerview.layoutmanager.layout.ViewBounds
+import com.rubensousa.dpadrecyclerview.spacing.DpadLinearSpacingDecoration
 import com.rubensousa.dpadrecyclerview.test.TestLayoutConfiguration
 import com.rubensousa.dpadrecyclerview.test.helpers.assertFocusAndSelection
 import com.rubensousa.dpadrecyclerview.test.helpers.assertItemAtPosition
 import com.rubensousa.dpadrecyclerview.test.helpers.getRelativeItemViewBounds
+import com.rubensousa.dpadrecyclerview.test.helpers.onRecyclerView
 import com.rubensousa.dpadrecyclerview.test.helpers.selectLastPosition
 import com.rubensousa.dpadrecyclerview.test.helpers.selectPosition
 import com.rubensousa.dpadrecyclerview.test.helpers.waitForAdapterUpdate
@@ -286,4 +289,171 @@ class AdapterMutationTest : DpadRecyclerViewTest() {
         // then
         assertFocusAndSelection(0)
     }
+
+    @Test
+    fun testDecorationsAreCorrectAfterRemovingItem() {
+        // given
+        val verticalItemSpacing = 24
+        val verticalEdgeSpacing = 200
+        val perpendicularSpacing = 64
+        val decoration = DpadLinearSpacingDecoration.create(
+            itemSpacing = verticalItemSpacing,
+            edgeSpacing = verticalEdgeSpacing,
+            perpendicularEdgeSpacing = perpendicularSpacing
+        )
+        onRecyclerView("Setting decoration") { recyclerView ->
+            recyclerView.addItemDecoration(decoration)
+        }
+
+        // when
+        mutateAdapter { adapter ->
+            adapter.removeFrom(2, adapter.itemCount - 2)
+        }
+        waitForAdapterUpdate()
+
+        // then
+        assertChildDecorations(
+            childIndex = 1,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = 0,
+                right = perpendicularSpacing,
+                bottom = verticalEdgeSpacing
+            ),
+        )
+    }
+
+    @Test
+    fun testDecorationsAreCorrectAfterAddingItem() {
+        // given
+        val verticalItemSpacing = 24
+        val verticalEdgeSpacing = 200
+        val perpendicularSpacing = 64
+        val decoration = DpadLinearSpacingDecoration.create(
+            itemSpacing = verticalItemSpacing,
+            edgeSpacing = verticalEdgeSpacing,
+            perpendicularEdgeSpacing = perpendicularSpacing
+        )
+        onRecyclerView("Setting decoration") { recyclerView ->
+            recyclerView.addItemDecoration(decoration)
+        }
+        mutateAdapter { adapter ->
+            adapter.setList(mutableListOf(0))
+            adapter.notifyDataSetChanged()
+        }
+        waitForAdapterUpdate()
+
+        // when
+        mutateAdapter { adapter ->
+            adapter.add()
+        }
+        waitForAdapterUpdate()
+
+        // then
+        assertChildDecorations(
+            childIndex = 0,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = verticalEdgeSpacing,
+                right = perpendicularSpacing,
+                bottom = verticalItemSpacing
+            ),
+        )
+    }
+
+    @Test
+    fun testDecorationsAreCorrectAfterMovingItem() {
+        // given
+        val verticalItemSpacing = 24
+        val verticalEdgeSpacing = 200
+        val perpendicularSpacing = 64
+        val decoration = DpadLinearSpacingDecoration.create(
+            itemSpacing = verticalItemSpacing,
+            edgeSpacing = verticalEdgeSpacing,
+            perpendicularEdgeSpacing = perpendicularSpacing
+        )
+        onRecyclerView("Setting decoration") { recyclerView ->
+            recyclerView.addItemDecoration(decoration)
+        }
+        mutateAdapter { adapter ->
+            adapter.setList(mutableListOf(0, 1))
+            adapter.notifyDataSetChanged()
+        }
+        waitForAdapterUpdate()
+
+        // when
+        mutateAdapter { adapter ->
+            adapter.move(0, 1)
+        }
+        waitForAdapterUpdate()
+
+        // then
+        assertChildDecorations(
+            childIndex = 0,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = verticalEdgeSpacing,
+                right = perpendicularSpacing,
+                bottom = verticalItemSpacing
+            ),
+        )
+        assertChildDecorations(
+            childIndex = 1,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = 0,
+                right = perpendicularSpacing,
+                bottom = verticalEdgeSpacing
+            ),
+        )
+    }
+
+    @Test
+    fun testDecorationsAreCorrectAfterUpdatingItems() {
+        // given
+        val verticalItemSpacing = 24
+        val verticalEdgeSpacing = 200
+        val perpendicularSpacing = 64
+        val decoration = DpadLinearSpacingDecoration.create(
+            itemSpacing = verticalItemSpacing,
+            edgeSpacing = verticalEdgeSpacing,
+            perpendicularEdgeSpacing = perpendicularSpacing
+        )
+        onRecyclerView("Setting decoration") { recyclerView ->
+            recyclerView.addItemDecoration(decoration)
+        }
+        mutateAdapter { adapter ->
+            adapter.setList(mutableListOf(0, 1, 2))
+            adapter.notifyDataSetChanged()
+        }
+        waitForAdapterUpdate()
+
+        // when
+        mutateAdapter { adapter ->
+            adapter.setList(mutableListOf(0, 1))
+            adapter.notifyDataSetChanged()
+        }
+        waitForAdapterUpdate()
+
+        // then
+        assertChildDecorations(
+            childIndex = 0,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = verticalEdgeSpacing,
+                right = perpendicularSpacing,
+                bottom = verticalItemSpacing
+            ),
+        )
+        assertChildDecorations(
+            childIndex = 1,
+            insets = ViewBounds(
+                left = perpendicularSpacing,
+                top = 0,
+                right = perpendicularSpacing,
+                bottom = verticalEdgeSpacing
+            ),
+        )
+    }
+
 }

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/DpadRecyclerView.kt

@@ -70,6 +70,19 @@ open class DpadRecyclerView @JvmOverloads constructor(
     private val focusableChildDrawingCallback = FocusableChildDrawingCallback()
     private val fadingEdge = FadingEdge()
     private val focusLossListeners = mutableListOf<OnFocusLostListener>()
+    private val adapterObserver = object : AdapterDataObserver() {
+        override fun onItemRangeRemoved(positionStart: Int, itemCount: Int) {
+            invalidateDecorationsSafely()
+        }
+
+        override fun onItemRangeInserted(positionStart: Int, itemCount: Int) {
+            invalidateDecorationsSafely()
+        }
+
+        override fun onItemRangeMoved(fromPosition: Int, toPosition: Int, itemCount: Int) {
+            invalidateDecorationsSafely()
+        }
+    }
     private val globalFocusChangeListener by lazy {
         GlobalFocusChangeListener(this) {
             focusLossListeners.forEach { listener ->
@@ -221,6 +234,22 @@ open class DpadRecyclerView @JvmOverloads constructor(
         return layout
     }
 
+    override fun setAdapter(adapter: Adapter<*>?) {
+        this.adapter?.unregisterAdapterDataObserver(adapterObserver)
+        super.setAdapter(adapter)
+        adapter?.registerAdapterDataObserver(adapterObserver)
+    }
+
+    private fun invalidateDecorationsSafely() {
+        if (isComputingLayout || scrollState != SCROLL_STATE_IDLE) {
+            post {
+                invalidateDecorationsSafely()
+            }
+        } else {
+            invalidateItemDecorations()
+        }
+    }
+
     final override fun setLayoutManager(layout: LayoutManager?) {
         super.setLayoutManager(layout)
         viewHolderTaskExecutor?.let {