Adjust homepage styles and layouts

- Fine tune the header text size and position
- Fix the header overlapping problem on the homepage and collapsing
  toolbar pages when configuration changes by adding android:id.
- New AppBarScrollingViewBehavior for the homepage to avoid manually
  offsetting the IA
- Correct the formula of counting search box height

Test: robotest, manual
Fixes: 177967923
Fixes: 177968564
Change-Id: Id3ed44f4296fa2a19d6890b009d3881a5c140bbd

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

@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2021 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.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.RobolectricTestRunner;
+import org.robolectric.RuntimeEnvironment;
+
+@RunWith(RobolectricTestRunner.class)
+public class HomepageAppBarScrollingViewBehaviorTest {
+
+    private HomepageAppBarScrollingViewBehavior mScrollingViewBehavior;
+    private Context mContext;
+
+    @Before
+    public void setUp() {
+        mContext = RuntimeEnvironment.application;
+        mScrollingViewBehavior = new HomepageAppBarScrollingViewBehavior(mContext,
+                Robolectric.buildAttributeSet().build());
+    }
+
+    @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);
+    }
+}