Java单击后退按钮两次以退出活动

在Java活动中：

boolean doubleBackToExitPressedonce = false;@Overridepublic void onBackPressed() {    if (doubleBackToExitPressedOnce) {        super.onBackPressed();        return;    }    this.doubleBackToExitPressedonce = true;    Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show();    new Handler().postDelayed(new Runnable() {        @Override        public void run() { doubleBackToExitPressedonce=false;         }    }, 2000);} 

在Kotlin活动中：

private var doubleBackToExitPressedonce = falseoverride fun onBackPressed() {        if (doubleBackToExitPressedOnce) { super.onBackPressed() return        }        this.doubleBackToExitPressedonce = true        Toast.makeText(this, "Please click BACK again to exit", Toast.LENGTH_SHORT).show()        Handler().postDelayed(Runnable { doubleBackToExitPressedonce = false }, 2000)    }

我认为此处理程序有助于在2秒后重置变量。