学步园

        Drawable normal = null;
        Drawable pressed = null;
        Drawable focus = null;

        StateListDrawable stateListDrawable = new StateListDrawable();
        // 注意该处的顺序，只要有一个状态与之相配，背景就会被换掉
        // 所以不要把大范围放在前面了，如果sd.addState(new[]{},normal)放在第一个的话，就没有什么效果了
        stateListDrawable.addState(new int[] { android.R.attr.state_enabled, android.R.attr.state_focused }, focus);
        stateListDrawable.addState(new int[] { android.R.attr.state_pressed, android.R.attr.state_enabled }, pressed);
        stateListDrawable.addState(new int[] { android.R.attr.state_focused }, focus);
        stateListDrawable.addState(new int[] { android.R.attr.state_pressed }, pressed);
        stateListDrawable.addState(new int[] { android.R.attr.state_enabled }, normal);
        stateListDrawable.addState(new int[] {}, normal);