Added FloatingAppBarScrollingViewBehavior

-Added FloatingAppBarScrollingViewBehavior for search bar. It can be scolling,
 transparent and overlapped the scrolling child view.
-Exchanged the position of NestedScrollView and AppBarLayout in
 settings_homepage_container.xml.
-Set the app bar height.

Change-Id: I6ef4c9001a1f893292fcbc825a0a9f2069b7286b
Fixes: 118886724
Test: robotest

res/layout/settings_homepage_container.xml

@@ -21,24 +21,17 @@
     android:layout_width="match_parent"
     android:layout_height="match_parent">
 
-    <com.google.android.material.appbar.AppBarLayout
-        android:layout_width="match_parent"
-        android:layout_height="wrap_content"
-        android:background="@android:color/transparent"
-        app:elevation="0dp">
-        <include layout="@layout/search_bar"/>
-    </com.google.android.material.appbar.AppBarLayout>
-
     <androidx.core.widget.NestedScrollView
         android:id="@+id/main_content_scrollable_container"
         android:layout_width="match_parent"
         android:layout_height="match_parent"
-        app:layout_behavior="@string/appbar_scrolling_view_behavior">
+        app:layout_behavior="com.android.settings.widget.FloatingAppBarScrollingViewBehavior">
 
         <LinearLayout
             android:layout_width="match_parent"
             android:layout_height="wrap_content"
             android:orientation="vertical"
+            android:paddingTop="@dimen/app_bar_height"
             android:descendantFocusability="blocksDescendants">
 
             <FrameLayout
@@ -55,4 +48,10 @@
 
         </LinearLayout>
     </androidx.core.widget.NestedScrollView>
+
+    <com.google.android.material.appbar.AppBarLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content">
+        <include layout="@layout/search_bar"/>
+    </com.google.android.material.appbar.AppBarLayout>
 </androidx.coordinatorlayout.widget.CoordinatorLayout>

res/values/dimens.xml

@@ -105,6 +105,8 @@
     <dimen name="search_bar_avatar_size">32dp</dimen>
     <dimen name="search_bar_avatar_start_margin">4dp</dimen>
     <dimen name="search_bar_avatar_end_margin">16dp</dimen>
+    <!-- appbar height is equal search bar height (48dp) plus search bar top and bottom margin  -->
+    <dimen name="app_bar_height">80dp</dimen>
 
     <!-- Dimensions for Wifi Assistant Card -->
     <dimen name="wifi_assistant_padding_top_bottom">16dp</dimen>

src/com/android/settings/widget/FloatingAppBarScrollingViewBehavior.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 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.
+ */
+
+package com.android.settings.widget;
+
+import android.content.Context;
+import android.graphics.Color;
+import android.util.AttributeSet;
+import android.view.View;
+
+import androidx.annotation.VisibleForTesting;
+import androidx.coordinatorlayout.widget.CoordinatorLayout;
+
+import com.google.android.material.appbar.AppBarLayout;
+
+/**
+ * This scrolling view behavior will set the background of the {@link AppBarLayout} as
+ * transparent and without the elevation. Also make header overlapped the scrolling child view.
+ */
+public class FloatingAppBarScrollingViewBehavior extends AppBarLayout.ScrollingViewBehavior {
+    private boolean initialized;
+
+    public FloatingAppBarScrollingViewBehavior(Context context, AttributeSet attrs) {
+        super(context, attrs);
+    }
+
+    @Override
+    public boolean onDependentViewChanged(CoordinatorLayout parent, View child, View dependency) {
+        boolean changed = super.onDependentViewChanged(parent, child, dependency);
+        if (!initialized && dependency instanceof AppBarLayout) {
+            initialized = true;
+            AppBarLayout appBarLayout = (AppBarLayout) dependency;
+            setAppBarLayoutTransparent(appBarLayout);
+        }
+        return changed;
+    }
+
+    @VisibleForTesting
+    void setAppBarLayoutTransparent(AppBarLayout appBarLayout) {
+        appBarLayout.setBackgroundColor(Color.TRANSPARENT);
+        appBarLayout.setTargetElevation(0);
+    }
+
+    @Override
+    protected boolean shouldHeaderOverlapScrollingChild() {
+        return true;
+    }
+}

tests/robotests/src/com/android/settings/widget/FloatingAppBarScrollingViewBehaviorTest.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright (C) 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.
+ */
+
+package com.android.settings.widget;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import android.content.Context;
+import android.graphics.Color;
+import android.graphics.drawable.ColorDrawable;
+
+import com.android.settings.R;
+import com.android.settings.testutils.SettingsRobolectricTestRunner;
+
+import com.google.android.material.appbar.AppBarLayout;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.robolectric.Robolectric;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(SettingsRobolectricTestRunner.class)
+public class FloatingAppBarScrollingViewBehaviorTest {
+
+    private FloatingAppBarScrollingViewBehavior mScrollingViewBehavior;
+    private Context mContext;
+
+    @Before
+    public void setUp() {
+        mContext = RuntimeEnvironment.application;
+        mScrollingViewBehavior = new FloatingAppBarScrollingViewBehavior(mContext,
+                Robolectric.buildAttributeSet().build());
+    }
+
+    @Test
+    public void shouldHeaderOverlapScrollingChild_returnTrue() {
+        assertThat(mScrollingViewBehavior.shouldHeaderOverlapScrollingChild()).isTrue();
+    }
+
+    @Test
+    public void setAppBarLayoutTransparent_backgroundDefaultAsWhite_shouldBeTransparent() {
+        mContext.setTheme(R.style.Theme_Settings_Home);
+        final AppBarLayout appBarLayout = new AppBarLayout(mContext);
+        appBarLayout.setBackgroundColor(Color.WHITE);
+        mScrollingViewBehavior.setAppBarLayoutTransparent(appBarLayout);
+        assertThat(((ColorDrawable) appBarLayout.getBackground()).getColor()).isEqualTo(
+                Color.TRANSPARENT);
+    }
+}