android 在布局中使用自定义属性

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:background="#ffffff"
android:orientation="vertical"
android:layout_height="match_parent">

<!--绘画一个圆形图片-->
<com.zhjy.measureview.CircleView
android:layout_width="wrap_content"
android:background="#000000"
android:layout_margin="20dp"
android:padding="20dp"
app:circle_color="@color/colorAccent"
android:layout_height="100dp" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>
<resources>
<declare-styleable name="CircleView">
<attr name="circle_color" format="color"/>
</declare-styleable>
</resources>