Issue 9656: Library projects don't support custom XML attributes for custom classes
Solution:
http://schemas.android.com/apk/res-auto as custom attributes' namespace URI, see Revisions for ADT 17.0.0:
http://schemas.android.com/apk/res-auto instead of the URI that includes the app package name. This URI is replaced with the app specific one at build time.
res与res-auto的区别
通常我们在布局文件中使用自定义属性的时候
会这样写
xmlns:app="http://schemas.android.com/apk/res/包路径"
但如果你当前工程是做为lib使用，那么你如上所写 ，会出现找不到自定义属性的错误 。
这时候你就必须 写成
xmlns:app="http://schemas.android.com/apk/res-auto/包路径"
