From ed3d2f91713af15521fa8db8e30c6c20bff3dd1d Mon Sep 17 00:00:00 2001
From: Chun-Ku Lin <chunkulin@google.com>
Date: Thu, 4 Jan 2024 07:19:51 +0000
Subject: [PATCH] Implemented nested scrolling parent in
 TextReadingPreviewPager

Flag: N/A
Bug: 317947238
Test: manual

Change-Id: I173881b84d5c5ff81c15a80a4de65fda59f5bf65
---
 .../accessibility_text_reading_preview.xml    |  3 +-
 .../TextReadingPreviewPager.java              | 30 +++++++++++++------
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/res/layout/accessibility_text_reading_preview.xml b/res/layout/accessibility_text_reading_preview.xml
index 95ea2e42349..830d9e66778 100644
--- a/res/layout/accessibility_text_reading_preview.xml
+++ b/res/layout/accessibility_text_reading_preview.xml
@@ -42,7 +42,8 @@
             android:id="@+id/preview_pager"
             android:layout_width="match_parent"
             android:layout_height="217dp"
-            android:contentDescription="@string/preview_pager_content_description" />
+            android:contentDescription="@string/preview_pager_content_description"
+            android:nestedScrollingEnabled="true" />
 
         <com.android.settings.widget.DotsPageIndicator
             android:id="@+id/page_indicator"
diff --git a/src/com/android/settings/accessibility/TextReadingPreviewPager.java b/src/com/android/settings/accessibility/TextReadingPreviewPager.java
index 5d431593d06..252d1213465 100644
--- a/src/com/android/settings/accessibility/TextReadingPreviewPager.java
+++ b/src/com/android/settings/accessibility/TextReadingPreviewPager.java
@@ -18,8 +18,7 @@ package com.android.settings.accessibility;
 
 import android.content.Context;
 import android.util.AttributeSet;
-import android.view.MotionEvent;
-import android.view.ViewGroup;
+import android.view.View;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
@@ -29,18 +28,31 @@ import androidx.viewpager.widget.ViewPager;
  * The view pager is used for displaying screen preview with different size configuration changes.
  */
 public class TextReadingPreviewPager extends ViewPager {
+
     public TextReadingPreviewPager(@NonNull Context context, @Nullable AttributeSet attrs) {
         super(context, attrs);
     }
 
     @Override
-    public boolean onInterceptTouchEvent(MotionEvent ev) {
-        final ViewGroup parent = (ViewGroup) getParent();
-        if (parent != null) {
-            // Avoid conflicting with the nested scroll view.
-            parent.requestDisallowInterceptTouchEvent(true);
-        }
+    public boolean onStartNestedScroll(View child, View target, int nestedScrollAxes) {
+        return (nestedScrollAxes & View.SCROLL_AXIS_VERTICAL) != 0;
+    }
 
-        return super.onInterceptTouchEvent(ev);
+    @Override
+    public void onNestedScrollAccepted(View child, View target, int axes) {
+        super.onNestedScrollAccepted(child, target, axes);
+        // Allow the nested scrollview inside of the view pager to be scrollable.
+        getParent().requestDisallowInterceptTouchEvent(true);
+    }
+
+    @Override
+    public void onNestedScroll(
+            View target, int dxConsumed, int dyConsumed, int dxUnconsumed, int dyUnconsumed) {
+        if (dyUnconsumed != 0) {
+            // Assume dyUnconsumed != 0 means the target has been scrolled to the end vertically.
+            // We could let the parent to consume the rest of the dyUnconsumed
+            getParent().requestDisallowInterceptTouchEvent(false);
+        }
+        super.onNestedScroll(target, dxConsumed, dyConsumed, dxUnconsumed, dyUnconsumed);
     }
 }