Add support for scrollbars

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

@@ -1,3 +1,18 @@
+/*
+ * Copyright 2023 Rúben Sousa
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
 package com.rubensousa.dpadrecyclerview
 
 import android.view.KeyEvent

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

@@ -23,7 +23,6 @@ import android.os.Parcelable
 import android.util.AttributeSet
 import android.view.View
 import android.view.ViewGroup
-import androidx.annotation.VisibleForTesting
 import androidx.core.view.accessibility.AccessibilityNodeInfoCompat
 import androidx.recyclerview.widget.RecyclerView
 import com.rubensousa.dpadrecyclerview.ChildAlignment
@@ -41,6 +40,7 @@ import com.rubensousa.dpadrecyclerview.layoutmanager.focus.SpanFocusFinder
 import com.rubensousa.dpadrecyclerview.layoutmanager.layout.LayoutInfo
 import com.rubensousa.dpadrecyclerview.layoutmanager.layout.LayoutPrefetchCollector
 import com.rubensousa.dpadrecyclerview.layoutmanager.layout.PivotLayout
+import com.rubensousa.dpadrecyclerview.layoutmanager.scroll.DpadScrollbarHelper
 import com.rubensousa.dpadrecyclerview.layoutmanager.scroll.LayoutScroller
 
 /**
@@ -169,6 +169,73 @@ class PivotLayoutManager(properties: Properties) : RecyclerView.LayoutManager()
         state: RecyclerView.State
     ): Int = pivotLayout.scrollVerticallyBy(dy, recycler, state)
 
+    override fun computeHorizontalScrollOffset(state: RecyclerView.State): Int {
+        return computeScrollOffset(state)
+    }
+
+    override fun computeVerticalScrollOffset(state: RecyclerView.State): Int {
+        return computeScrollOffset(state)
+    }
+
+    override fun computeHorizontalScrollExtent(state: RecyclerView.State): Int {
+        return computeScrollExtent(state)
+    }
+
+    override fun computeVerticalScrollExtent(state: RecyclerView.State): Int {
+        return computeScrollExtent(state)
+    }
+
+    override fun computeHorizontalScrollRange(state: RecyclerView.State): Int {
+        return computeScrollRange(state)
+    }
+
+    override fun computeVerticalScrollRange(state: RecyclerView.State): Int {
+        return computeScrollRange(state)
+    }
+
+    private fun computeScrollOffset(state: RecyclerView.State): Int {
+        if (childCount == 0) {
+            return 0
+        }
+        return DpadScrollbarHelper.computeScrollOffset(
+            state = state,
+            orientationHelper = layoutInfo.orientationHelper,
+            startChild = layoutInfo.findFirstVisibleChild(),
+            endChild = layoutInfo.findLastVisibleChild(),
+            lm = this,
+            smoothScrollbarEnabled = true,
+            reverseLayout = configuration.reverseLayout
+        )
+    }
+
+    private fun computeScrollExtent(state: RecyclerView.State): Int {
+        if (childCount == 0) {
+            return 0
+        }
+        return DpadScrollbarHelper.computeScrollExtent(
+            state = state,
+            orientationHelper = layoutInfo.orientationHelper,
+            startChild = layoutInfo.findFirstVisibleChild(),
+            endChild = layoutInfo.findLastVisibleChild(),
+            lm = this,
+            smoothScrollbarEnabled = true,
+        )
+    }
+
+    private fun computeScrollRange(state: RecyclerView.State): Int {
+        if (childCount == 0) {
+            return 0
+        }
+        return  DpadScrollbarHelper.computeScrollRange(
+            state = state,
+            orientationHelper = layoutInfo.orientationHelper,
+            startChild = layoutInfo.findFirstVisibleChild(),
+            endChild = layoutInfo.findLastVisibleChild(),
+            lm = this,
+            smoothScrollbarEnabled = true,
+        )
+    }
+
     override fun scrollToPosition(position: Int) {
         scroller.scrollToPosition(position)
     }
@@ -571,9 +638,4 @@ class PivotLayoutManager(properties: Properties) : RecyclerView.LayoutManager()
         }
     }
 
-    @VisibleForTesting
-    internal fun getFocusFinderSpanCount(): Int {
-        return spanFocusFinder.spanCount
-    }
-
 }

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

@@ -281,6 +281,22 @@ internal class LayoutInfo(
         )
     }
 
+    fun findFirstVisibleChild(): View? {
+        val childPosition = findFirstVisiblePosition()
+        if (childPosition == RecyclerView.NO_POSITION) {
+            return null
+        }
+        return layout.findViewByPosition(childPosition)
+    }
+
+    fun findLastVisibleChild(): View? {
+        val childPosition = findLastVisiblePosition()
+        if (childPosition == RecyclerView.NO_POSITION) {
+            return null
+        }
+        return layout.findViewByPosition(childPosition)
+    }
+
     /**
      * @param startIndex index at which the search should start
      * @param endIndex index at which the search should stop (not inclusive)

dpadrecyclerview/src/main/java/com/rubensousa/dpadrecyclerview/layoutmanager/scroll/DpadScrollbarHelper.kt

@@ -0,0 +1,137 @@
+/*
+ * Copyright 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Copyright 2023 Rúben Sousa
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.rubensousa.dpadrecyclerview.layoutmanager.scroll
+
+import android.view.View
+import androidx.recyclerview.widget.OrientationHelper
+import androidx.recyclerview.widget.RecyclerView
+
+/**
+ * A helper class to do scroll offset calculations.
+ * Adapted from ScrollbarHelper of androidx.recyclerview
+ */
+internal object DpadScrollbarHelper {
+
+    /**
+     * @param startChild View closest to start of the list. (top or left)
+     * @param endChild   View closest to end of the list (bottom or right)
+     */
+    fun computeScrollOffset(
+        state: RecyclerView.State,
+        orientationHelper: OrientationHelper,
+        startChild: View?,
+        endChild: View?,
+        lm: RecyclerView.LayoutManager,
+        smoothScrollbarEnabled: Boolean,
+        reverseLayout: Boolean
+    ): Int {
+        if (lm.childCount == 0 || state.itemCount == 0 || startChild == null || endChild == null) {
+            return 0
+        }
+        val minPosition = Math.min(lm.getPosition(startChild), lm.getPosition(endChild))
+        val maxPosition = Math.max(lm.getPosition(startChild), lm.getPosition(endChild))
+        val itemsBefore = if (reverseLayout) {
+            Math.max(0, state.itemCount - maxPosition - 1)
+        } else {
+            Math.max(0, minPosition)
+        }
+        if (!smoothScrollbarEnabled) {
+            return itemsBefore
+        }
+        val laidOutArea = Math.abs(
+            orientationHelper.getDecoratedEnd(endChild)
+                    - orientationHelper.getDecoratedStart(startChild)
+        )
+        val itemRange = Math.abs((lm.getPosition(startChild) - lm.getPosition(endChild))) + 1
+        val avgSizePerRow = laidOutArea.toFloat() / itemRange
+        return Math.round(
+            itemsBefore * avgSizePerRow + ((orientationHelper.startAfterPadding
+                    - orientationHelper.getDecoratedStart(startChild)))
+        )
+    }
+
+    /**
+     * @param startChild View closest to start of the list. (top or left)
+     * @param endChild   View closest to end of the list (bottom or right)
+     */
+    fun computeScrollExtent(
+        state: RecyclerView.State,
+        orientationHelper: OrientationHelper,
+        startChild: View?,
+        endChild: View?,
+        lm: RecyclerView.LayoutManager,
+        smoothScrollbarEnabled: Boolean
+    ): Int {
+        if ((lm.childCount == 0) || (state.itemCount == 0) || (startChild == null
+                    ) || (endChild == null)
+        ) {
+            return 0
+        }
+        if (!smoothScrollbarEnabled) {
+            return Math.abs(lm.getPosition(startChild) - lm.getPosition(endChild)) + 1
+        }
+        val extend = (orientationHelper.getDecoratedEnd(endChild)
+                - orientationHelper.getDecoratedStart(startChild))
+        return Math.min(orientationHelper.totalSpace, extend)
+    }
+
+    /**
+     * @param startChild View closest to start of the list. (top or left)
+     * @param endChild   View closest to end of the list (bottom or right)
+     */
+    fun computeScrollRange(
+        state: RecyclerView.State,
+        orientationHelper: OrientationHelper,
+        startChild: View?,
+        endChild: View?,
+        lm: RecyclerView.LayoutManager,
+        smoothScrollbarEnabled: Boolean
+    ): Int {
+        if ((lm.childCount == 0)
+            || (state.itemCount == 0)
+            || (startChild == null)
+            || (endChild == null)
+        ) {
+            return 0
+        }
+        if (!smoothScrollbarEnabled) {
+            return state.itemCount
+        }
+        // smooth scrollbar enabled. try to estimate better.
+        val laidOutArea = (orientationHelper.getDecoratedEnd(endChild)
+                - orientationHelper.getDecoratedStart(startChild))
+        val laidOutRange = (Math.abs(lm.getPosition(startChild) - lm.getPosition(endChild)) + 1)
+        // estimate a size for full list.
+        return (laidOutArea.toFloat() / laidOutRange * state.itemCount).toInt()
+    }
+
+}

sample/src/main/java/com/rubensousa/dpadrecyclerview/sample/ui/screen/text/TextScrollingFragment.kt

@@ -29,7 +29,7 @@ class TextScrollingFragment : Fragment(R.layout.screen_text_scrolling) {
         val adapter = TextAdapter()
         val text = view.resources.getString(R.string.placeholder_text)
         val list = mutableListOf<String>()
-        repeat(50) {
+        repeat(20) {
             list.add(text)
         }
         adapter.submitList(list)

sample/src/main/res/drawable/scrollbar_thumb.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+
+    <corners android:radius="4dp" />
+    <solid android:color="@color/white" />
+
+</shape>

sample/src/main/res/drawable/scrollbar_track.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+
+    <solid android:color="@color/black" />
+
+</shape>

sample/src/main/res/layout/screen_text_scrolling.xml

@@ -48,6 +48,12 @@
         android:layout_height="match_parent"
         android:layout_marginStart="24dp"
         android:background="@color/list_text_background"
+        android:fadeScrollbars="false"
+        android:scrollbarAlwaysDrawVerticalTrack="true"
+        android:scrollbarSize="6dp"
+        android:scrollbarThumbVertical="@drawable/scrollbar_thumb"
+        android:scrollbarTrackVertical="@drawable/scrollbar_track"
+        android:scrollbars="vertical"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintEnd_toStartOf="@id/guideline"
         app:layout_constraintStart_toEndOf="@id/backButton"