安卓：两次单击后退按钮退出活动 [英] Android: clicking TWICE the back button to exit activity

问题描述

我已经注意到这种模式在许多Android应用和游戏的最近：单击后退按钮退出的应用程序，吐司来了一个时类似的消息请单击后退再次退出。

我不知道，因为我看到它越来越多的时候，是一个内置的，你能以某种方式在活动中访问功能？我已经看了很多类的源$ C ​​$ C，但我似乎无法找到任何东西。

当然，我能想到的几种方法可以很容易地实现相同的功能（最简单的可能是保持一个布尔值的活动，指示用户是否已经点击一次...），但我不知道是否有一些已经在这里了。

修改：作为@LAS_VEGAS提到的，我并没有真正指的是在传统意义上的退出。 （即终止）我的意思是要回什么是开放之前，应用程序启动活动发起，如果是有道理的：）

解决方案

 布尔doubleBackToExit pressedOnce = FALSE;

@覆盖
公共无效onBack pressed（）{
    如果（doubleBackToExit pressedOnce）{
        super.onBack pressed（）;
        返回;
    }

    this.doubleBackToExit pressedOnce = TRUE;
    Toast.makeText（这一点，请再次点击返回退出，Toast.LENGTH_SHORT）.show（）;

    新的处理程序（）。postDelayed（新的Runnable（）{

        @覆盖
        公共无效的run（）{
            doubleBackToExit pressedOnce = FALSE;
        }
    }，2000）;
}
 

我觉得这个处理程序有助于经过2秒钟，重设变量。

I've noticed this pattern in a lot of Android apps and games recently: when clicking the back button to "exit" the application, a Toast comes up with a message similar to "Please click BACK again to exit".

I was wondering, as I'm seeing it more and more often, is that a built-in feature that you can somehow access in an activity? I've looked at the source code of many classes but I can't seem to find anything about that.

Of course, I can think about a few ways to achieve the same functionality quite easily (the easiest is probably to keep a boolean in the activity that indicates whether the user already clicked once...) but I was wondering if there's something already here.

EDIT: As @LAS_VEGAS mentioned, I didn't really mean "exit" in the traditional meaning. (i.e. terminated) I meant "going back to whatever was open before the application start activity was launched", if that makes sense :)

解决方案

boolean doubleBackToExitPressedOnce = false;

@Override
public 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);
} 

I Think this handler helps to reset the variable after 2 second.

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