android點擊手機返回鍵觸發事件

點擊返回鍵，觸發onKeyDown事件：

@Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
            checkExit();
            return true;
        }
        return super.onKeyDown(keyCode, event);
    }