StateListDrawable 按下不能自动变化的问题

StateListDrawable drawable = new StateListDrawable();

drawable.addState(new int[] { android.R.attr.state_pressed,
android.R.attr.state_enabled }, new ColorDrawable(Color.GREEN));
drawable.addState(new int[] {}, new ColorDrawable(Color.BLUE));

1. 系统识别的按下状态为 new int[] { android.R.attr.state_pressed,
android.R.attr.state_enabled }

2. 默认的Drawable应该写在后面