Fix the preview couldn't be scrolled up and down when showing the scroll bar.

Actions:
1) Add the specific attribute to disallow parent view intercept the touch event of child view to avoid conflicting with the nested scroll view.
2) Add the scroll view into the page of the mail content preview.

Bug: 220078816
Test: manual test
Change-Id: I7f3b2afdf76e501386d9080e7a0eed8b92e28d3b
diff --git a/res/layout/accessibility_text_reading_preview.xml b/res/layout/accessibility_text_reading_preview.xml
index 91fb0a0..4b70bb4 100644
--- a/res/layout/accessibility_text_reading_preview.xml
+++ b/res/layout/accessibility_text_reading_preview.xml
@@ -37,7 +37,7 @@
             android:text="@string/screen_zoom_preview_title"
             style="@style/AccessibilityTextReadingPreviewTitle" />
 
-        <androidx.viewpager.widget.ViewPager
+        <com.android.settings.accessibility.TextReadingPreviewPager
             android:id="@+id/preview_pager"
             android:layout_width="match_parent"
             android:layout_height="217dp"
diff --git a/res/layout/accessibility_text_reading_preview_mail_content.xml b/res/layout/accessibility_text_reading_preview_mail_content.xml
index 941535f..e55d389 100644
--- a/res/layout/accessibility_text_reading_preview_mail_content.xml
+++ b/res/layout/accessibility_text_reading_preview_mail_content.xml
@@ -15,35 +15,43 @@
     limitations under the License.
 -->
 
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<androidx.core.widget.NestedScrollView
+    xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
-    android:layout_height="wrap_content"
-    android:orientation="vertical">
+    android:layout_height="match_parent"
+    android:fillViewport="true"
+    android:importantForAccessibility="noHideDescendants">
 
-    <TextView
-        android:id="@+id/subject"
+    <LinearLayout
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
-        android:text="@string/accessibility_text_reading_preview_mail_subject"
-        android:textSize="14sp"
-        android:textAppearance="?android:attr/textAppearanceMedium"
-        android:textColor="?android:attr/textColorPrimary"/>
+        android:orientation="vertical">
 
-    <TextView
-        android:id="@+id/from"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:paddingBottom="16dp"
-        android:paddingTop="11dp"
-        android:textSize="12sp"
-        android:text="@string/accessibility_text_reading_preview_mail_from"
-        android:textColor="?android:attr/textColorSecondary" />
+        <TextView
+            android:id="@+id/subject"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:text="@string/accessibility_text_reading_preview_mail_subject"
+            android:textSize="14sp"
+            android:textAppearance="?android:attr/textAppearanceMedium"
+            android:textColor="?android:attr/textColorPrimary"/>
 
-    <TextView
-        android:id="@+id/content"
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:textSize="13sp"
-        android:text="@string/accessibility_text_reading_preview_mail_content"
-        android:textColor="?android:attr/textColorPrimary"/>
-</LinearLayout>
+        <TextView
+            android:id="@+id/from"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:paddingBottom="16dp"
+            android:paddingTop="11dp"
+            android:textSize="12sp"
+            android:text="@string/accessibility_text_reading_preview_mail_from"
+            android:textColor="?android:attr/textColorSecondary"/>
+
+        <TextView
+            android:id="@+id/content"
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:textSize="13sp"
+            android:text="@string/accessibility_text_reading_preview_mail_content"
+            android:textColor="?android:attr/textColorPrimary"/>
+    </LinearLayout>
+</androidx.core.widget.NestedScrollView>
diff --git a/src/com/android/settings/accessibility/TextReadingPreviewPager.java b/src/com/android/settings/accessibility/TextReadingPreviewPager.java
new file mode 100644
index 0000000..5d43159
--- /dev/null
+++ b/src/com/android/settings/accessibility/TextReadingPreviewPager.java
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2022 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.
+ */
+
+package com.android.settings.accessibility;
+
+import android.content.Context;
+import android.util.AttributeSet;
+import android.view.MotionEvent;
+import android.view.ViewGroup;
+
+import androidx.annotation.NonNull;
+import androidx.annotation.Nullable;
+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);
+        }
+
+        return super.onInterceptTouchEvent(ev);
+    }
+}