两个图片背景不断旋转

indeterminate
adj.  不确的, 含混的, 不确定的

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<ProgressBar
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"
        android:indeterminateBehavior="repeat"
        android:indeterminateDrawable="@drawable/progress_big" />
		
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<?xml version="1.0" encoding="utf-8"?>
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">

    <item>
        <rotate
            android:drawable="@drawable/spinner_big_inner"
            android:fromDegrees="0"
            android:toDegrees="-1080"/>
    </item>

    <item>
        <rotate
            android:drawable="@drawable/spinner_big_outer"
            android:fromDegrees="0"
            android:toDegrees="720"/>
    </item>

</layer-list>

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