具有状态的Drawable: StateListDrawable -> DrawableContainer
Drawable.onStateChange()
View.setPressed()对Background drawable状态的操作;
View.setPressed
View.refreshDrawableStateView.drawableStateChanged
View.mBackgroundDrawable.setState(state);
View中释放PressedState的逻辑:
View.onTouchEvent()
case ACTION_UP:
setPressed(true); //设置按下状态
post(mPerformClick); //performClick();回调点击事件
post(mUnsetPressedState); //释放按下状态