<animation-list xmlns:android="http://schemas.android.com/apk/res/android"
    android:oneshot="false">
    <item
        android:drawable="@drawable/loading1"   动画图片
        android:duration="50" />                间隔时间
    <item
        android:drawable="@drawable/loading2"
        android:duration="50" />
    <item
        android:drawable="@drawable/loading3"
        android:duration="50" />
    <item
        android:drawable="@drawable/loading4"
        android:duration="50" />
    <item
        android:drawable="@drawable/loading5"
        android:duration="50" />
</animation-list>