渐变背景

Gradient

1.在drawable文件夹下创建一些渐变颜色文件
color1.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="#614385"
        android:endColor="#516395"
        android:angle="0"/>
</shape>

color2.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="#5f2c82"
        android:endColor="#49a09d"
        android:angle="45"/>
</shape>

color3.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="#4776E6"
        android:endColor="#8E54E9"
        android:angle="90"/>
</shape>

color4.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <gradient
        android:startColor="#7141e2"
        android:endColor="#d46cb3"
        android:angle="135"/>
</shape>

2.使用上面的渐变颜色创建一个动画列表animation_list.xml

<?xml version="1.0" encoding="utf-8"?>
<animation-list xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:drawable="@drawable/color1"
        android:duration="10000" />
    <item
        android:drawable="@drawable/color2"
        android:duration="10000" />
    <item
        android:drawable="@drawable/color3"
        android:duration="10000" />
    <item
        android:drawable="@drawable/color4"
        android:duration="10000" />
</animation-list>

3.将动画列表应用为Activity布局的顶级视图

<android.support.constraint.ConstraintLayout
            android:id="@+id/cl_home"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@drawable/animation_list"
            android:id="@+id/container">

    <!-- Child Views -->

</android.support.constraint.ConstraintLayout>

4.在Activity里使用AnimationDrawable实现过渡切换

ConstraintLayoutcontainer = findViewById(R.id.container);

AnimationDrawable anim = (AnimationDrawable) container.getBackground();
anim.setEnterFadeDuration(6000);
anim.setExitFadeDuration(2000);

// Starting animation:- start the animation on onResume.
@Override
protected void onResume() {
    super.onResume();
    if (anim != null && !anim.isRunning())
        anim.start();
}
      
// Stopping animation:- stop the animation on onPause.
@Override
protected void onPause() {
    super.onPause();
    if (anim != null && anim.isRunning())
        anim.stop();
}