Android双击返回按钮退出程序

    //双击退出事件
    @Override
    public boolean onKeyDown(int keyCode, KeyEvent event) {
        if(keyCode == KeyEvent.KEYCODE_BACK)
             {
                 ExitApp();      //调用双击退出函数
            }
        return false;
    }
    private long exitTime = 0;
    public void ExitApp() {
        if ((System.currentTimeMillis() - exitTime) > 2000)
        {
            Snackbar.make(lstData, "再按一次退出程序", Snackbar.LENGTH_LONG).setAction("Action", null).show();
            exitTime = System.currentTimeMillis();
        } else
        {
            finish();
            System.exit(0);
        }

    }