Android -purpose of useLevel in shape tag
It is for ProgressBars. For example this gist uses a ring shape as a progress drawable.
res/drawable/github_232_circular.xml:
<shape xmlns:android="http://schemas.android.com/apk/res/android" android:innerRadiusRatio="2.3" android:shape="ring" android:thickness="3.8sp" android:useLevel="true"> <solid android:color="#ff0000" /></shape>In your layout:
<ProgressBar android:id="@+id/progress" style="?android:attr/progressBarStyleHorizontal" android:layout_width="64dp" android:layout_height="64dp" android:layout_gravity="top|end" android:max="100" android:progress="0" android:progressDrawable="@drawable/github_232_circular"/>Basically, useLevel makes it so the drawable can be drawn partially. For example there is a method ImageView.setImageLevel() that lets you set a "level," e.g. 25% progress, so the ring drawable would be drawn as a quarter-circle. And ProgressBar.setProgress() does the same thing, updating the "level" of the drawable you've set on the ProgressBar.