Drawable 下定义一个会旋转的ui

<rotate
    xmlns:android="http:///apk/res/android"
    android:fromDegrees="0"
    android:toDegrees="360"
    android:pivotX="50%"
    android:pivotY="50%"
    android:drawable="@drawable/default_ptr_rotate"
    <shape
        android:innerRadius="12dp"
        android:shape="ring"
        android:thickness="3dp"
        android:useLevel="false"
        <gradient
            android:endColor="@color/cn_write"
            android:centerColor="@color/cn_write"
            android:startColor="@color/cn_blue"
    </shape>
</rotate>