图形显示不出来咋办

<item>
<shape>
<gradient
android:startColor='#4CB7EF'
android:endColor='#4cb7ef'
android:angle='0' />
<corners
android:topLeftRadius="100dp"
android:topRightRadius="100dp"
android:bottomRightRadius="100dp"
android:bottomLeftRadius="100dp" />
</shape>
</item>

设置控件大小为具体值试看

没定义任何宽高，显示个p啊