Restore to previous layout anchor if user scrolls via touch

docs/changelog.md

@@ -2,6 +2,15 @@
 
 ## Version 1.2.0
 
+### 1.2.0-alpha02
+
+2023-12-27
+
+#### Bug fixes
+
+- Fixed layout jumping to the top when the user scrolls with touch events ([#171](https://github.com/rubensousa/DpadRecyclerView/issues/171))
+- Fixed alignment configuration not being respected for small lists ([#172](https://github.com/rubensousa/DpadRecyclerView/issues/172))
+
 ### 1.2.0-alpha01
 
 2023-11-25

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

@@ -376,7 +376,7 @@ open class DpadRecyclerView @JvmOverloads constructor(
 
     final override fun onRtlPropertiesChanged(layoutDirection: Int) {
         super.onRtlPropertiesChanged(layoutDirection)
-        pivotLayoutManager?.onRtlPropertiesChanged()
+        pivotLayoutManager?.onRtlPropertiesChanged(layoutDirection)
     }
 
     final override fun smoothScrollBy(dx: Int, dy: Int) {

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/layoutmanager/LayoutConfiguration.kt

@@ -132,6 +132,9 @@ internal class LayoutConfiguration(properties: Properties) {
     var recycleChildrenOnDetach: Boolean = false
         private set
 
+    var keepLayoutAnchor: Boolean = false
+        private set
+
     init {
         setSpanCount(properties.spanCount)
         setOrientation(properties.orientation)
@@ -250,4 +253,10 @@ internal class LayoutConfiguration(properties: Properties) {
         }
     }
 
+    // This flag will be used to try to keep layout consistency
+    // whenever the user scrolls the layout using touch events
+    fun setKeepLayoutAnchor(keep: Boolean) {
+        keepLayoutAnchor = keep
+    }
+
 }

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/layoutmanager/PivotLayoutManager.kt

@@ -50,6 +50,7 @@ import com.rubensousa.dpadrecyclerview.layoutmanager.scroll.LayoutScroller
  */
 class PivotLayoutManager(properties: Properties) : RecyclerView.LayoutManager() {
 
+    private var layoutDirection: Int = View.LAYOUT_DIRECTION_LTR
     private val configuration = LayoutConfiguration(properties)
     private val layoutInfo = LayoutInfo(this, configuration)
     private val pivotSelector = PivotSelector(this, layoutInfo)
@@ -389,7 +390,11 @@ class PivotLayoutManager(properties: Properties) : RecyclerView.LayoutManager()
         pivotLayout.onRestoreInstanceState(state)
     }
 
-    internal fun onRtlPropertiesChanged() {
+    internal fun onRtlPropertiesChanged(layoutDirection: Int) {
+        if (this.layoutDirection == layoutDirection) {
+            return
+        }
+        this.layoutDirection = layoutDirection
         requestLayout()
     }
 
@@ -406,6 +411,7 @@ class PivotLayoutManager(properties: Properties) : RecyclerView.LayoutManager()
     internal fun getConfig() = configuration
 
     internal fun setScrollingFromTouchEvent(isTouching: Boolean) {
+        configuration.setKeepLayoutAnchor(isTouching)
         isScrollingFromTouchEvent = isTouching
     }
 

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/layoutmanager/focus/FocusDispatcher.kt

@@ -266,6 +266,7 @@ internal class FocusDispatcher(
      * Request focus to the current pivot if it exists
      */
     fun onRequestFocusInDescendants(direction: Int, previouslyFocusedRect: Rect?): Boolean {
+        if (configuration.isFocusSearchDisabled) return false
         val view = layout.findViewByPosition(pivotSelector.position) ?: return false
         return view.requestFocus(direction, previouslyFocusedRect)
     }

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/layoutmanager/layout/PivotLayout.kt

@@ -38,7 +38,7 @@ internal class PivotLayout(
     private val configuration: LayoutConfiguration,
     private val pivotSelector: PivotSelector,
     private val scroller: LayoutScroller,
-    private val layoutInfo: LayoutInfo
+    private val layoutInfo: LayoutInfo,
 ) {
 
     companion object {
@@ -50,6 +50,7 @@ internal class PivotLayout(
     private var structureEngineer = createStructureEngineer()
     private val layoutCompleteListeners = ArrayList<DpadRecyclerView.OnLayoutCompletedListener>()
     private val itemChanges = ItemChanges()
+    private var anchor: Int? = null
 
     fun updateStructure() {
         structureEngineer = createStructureEngineer()
@@ -91,7 +92,7 @@ internal class PivotLayout(
     private fun preLayoutChildren(
         pivotPosition: Int,
         recycler: RecyclerView.Recycler,
-        state: RecyclerView.State
+        state: RecyclerView.State,
     ) {
         val childCount = layoutManager.childCount
         if (childCount == 0) {
@@ -116,8 +117,16 @@ internal class PivotLayout(
             structureEngineer.logChildren()
         }
 
+        if (configuration.keepLayoutAnchor) {
+            saveAnchorState()
+        }
+
         structureEngineer.layoutChildren(pivotSelector.position, itemChanges, recycler, state)
 
+        if (configuration.keepLayoutAnchor) {
+            restoreAnchorState(recycler, state)
+        }
+
         if (DpadRecyclerView.DEBUG) {
             Log.i(TAG, "LayoutFinished")
             structureEngineer.logChildren()
@@ -126,6 +135,41 @@ internal class PivotLayout(
         structureEngineer.onLayoutFinished()
     }
 
+    private fun saveAnchorState() {
+        val currentPivotPosition = if (!layoutInfo.shouldReverseLayout()) {
+            layoutInfo.findFirstVisiblePosition()
+        } else {
+            layoutInfo.findLastVisiblePosition()
+        }
+        if (currentPivotPosition == RecyclerView.NO_POSITION) {
+            return
+        }
+        pivotSelector.update(currentPivotPosition)
+        layoutInfo.findViewByPosition(currentPivotPosition)?.let { view ->
+            anchor = if (!layoutInfo.shouldReverseLayout()) {
+                layoutInfo.getDecoratedStart(view)
+            } else {
+                layoutInfo.getDecoratedEnd(view)
+            }
+        }
+    }
+
+    private fun restoreAnchorState(recycler: RecyclerView.Recycler, state: RecyclerView.State) {
+        anchor?.let { previousAnchor ->
+            if (pivotSelector.position != RecyclerView.NO_POSITION) {
+                layoutInfo.findViewByPosition(pivotSelector.position)?.let { view ->
+                    val currentAnchor = if (!layoutInfo.shouldReverseLayout()) {
+                        layoutInfo.getDecoratedStart(view)
+                    } else {
+                        layoutInfo.getDecoratedEnd(view)
+                    }
+                    scrollBy(currentAnchor - previousAnchor, recycler, state)
+                }
+            }
+            anchor = null
+        }
+    }
+
     fun reset() {
         structureEngineer.clear()
     }
@@ -173,7 +217,7 @@ internal class PivotLayout(
     fun scrollHorizontallyBy(
         dx: Int,
         recycler: RecyclerView.Recycler,
-        state: RecyclerView.State
+        state: RecyclerView.State,
     ): Int {
         if (configuration.isVertical()) {
             return 0
@@ -184,7 +228,7 @@ internal class PivotLayout(
     fun scrollVerticallyBy(
         dy: Int,
         recycler: RecyclerView.Recycler,
-        state: RecyclerView.State
+        state: RecyclerView.State,
     ): Int {
         if (configuration.isHorizontal()) {
             return 0
@@ -216,7 +260,7 @@ internal class PivotLayout(
     private fun scrollBy(
         offset: Int,
         recycler: RecyclerView.Recycler,
-        state: RecyclerView.State
+        state: RecyclerView.State,
     ): Int {
         // Do nothing if we don't have children
         if (state.itemCount == 0 || offset == 0 || !configuration.isLayoutEnabled) {
@@ -242,7 +286,7 @@ internal class PivotLayout(
         val selectedPosition: Int,
         val isLoopingStart: Boolean,
         val isLoopingAllowed: Boolean,
-        val loopDirection: DpadLoopDirection
+        val loopDirection: DpadLoopDirection,
     ) : Parcelable {
 
         companion object CREATOR : Parcelable.Creator<SavedState> {

gradle.properties

@@ -22,4 +22,4 @@ kotlin.code.style=official
 # thereby reducing the size of the R class for that library
 android.nonTransitiveRClass=true
 android.enableR8.fullMode=true
-LIBRARY_VERSION=1.2.0-alpha01
+LIBRARY_VERSION=1.2.0-alpha02

mkdocs.yml

@@ -24,7 +24,7 @@ theme:
 
 extra:
   dpadrecyclerview:
-    version: '1.2.0-alpha01'
+    version: '1.2.0-alpha02'
   social:
     - icon: 'fontawesome/brands/github'
       link: 'https://github.com/rubensousa/DpadRecyclerView'