android:duplicateParentState="true"

android:duplicateParentState

When this attribute is set to true, the view gets its drawable state (focused, pressed, etc.) from its direct parent rather than from itself.

Must be a boolean value, either "true" or "false".

This may also be a reference to a resource (in the form "@[package:]type:name") or theme attribute (in the form "?[package:][type:]name") containing a value of this type.

This corresponds to the global attribute resource symbol duplicateParentState.

View的一个比较实用的属性

如果设置此属性，将直接从父容器中获取绘图状态（光标，按下等）。 注意仅仅是获取绘图状态，而没有获取事件，也就是你点一下LinearLayout时Button有被点击的效果，但是不执行点击事件“