SystemUI 的通知背景颜色更改

本文基于 android_13.0.0_r1 讲解

类 ActivatableNotificationView 的方法 initBackground , 用R.drawable.notification_material_bg定义背景, 源码如下：

/**
 * Sets the custom background on {@link #mBackgroundNormal}
 * This method can also be used to reload the backgrounds on both of those views, which can
 * be useful in a configuration change.
 */
protected void initBackground() {
    mBackgroundNormal.setCustomBackground(R.drawable.notification_material_bg);
}

R.drawable.notification_material_bg定义了背景颜色，但没有明确指定形状

<?xml version="1.0" encoding="utf-8"?>
<!--
  ~ Copyright (C) 2014 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
  -->

<ripple xmlns:android="http://schemas.android.com/apk/res/android"
        xmlns:androidprv="http://schemas.android.com/apk/prv/res/android"
        android:color="?android:attr/colorControlHighlight">
    <item>
        <shape>
            <solid android:color="@color/colorSurface" />
        </shape>
    </item>
</ripple>

而继承类 ActivatableNotificationView 的类有 NotificationShelf、ExpandableNotificationRow。