安卓：退出应用程序时，preSS后退按钮 [英] Android: Quit application when press back button

问题描述

在我的应用程序，我想从应用程序退出时，preSS后退按钮，这是我的code：

  @覆盖
    公共无效onBack pressed（）{
        新AlertDialog.Builder（本）.setIcon（android.R.drawable.ic_dialog_alert）.setTitle（退出）
                .setMessage（你确定要退出吗？）
                .setPositiveButton（是，新DialogInterface.OnClickListener（）{
                    @覆盖
                    公共无效的onClick（DialogInterface对话，诠释它）{
                        完（）;
                    }
                }）setNegativeButton（否，空）.show（）。
    }
 

这是正常工作，但是当我从应用程序退出并不完全退出，并显示空白页面，我的应用程序的标志，当我再次preSS后退按钮退出应用程序，该如何解决呢???

编辑：

我完全使用code，而不是上面的，但我的应用程序退出，但我希望它运行在后台并没有完全退出，我该怎么办呢？

  @覆盖
    公共无效onBack pressed（）{
        新AlertDialog.Builder（本）.setIcon（android.R.drawable.ic_dialog_alert）.setTitle（退出）
                .setMessage（你确定吗？）
                .setPositiveButton（是，新DialogInterface.OnClickListener（）{
                    @覆盖
                    公共无效的onClick（DialogInterface对话，诠释它）{

                        意向意图=新的意图（Intent.ACTION_MAIN）;
                        intent.addCategory（Intent.CATEGORY_HOME）;
                        intent.setFlags（Intent.FLAG_ACTIVITY_NEW_TASK）;
                        startActivity（意向）;
                        完（）;
                    }
                }）setNegativeButton（否，空）.show（）。
    }
 

解决方案

在preSS回来，然后你完成当前的活动（比如A），您将看到您的应用程序的标志空白的活动（比如B）这只是意味着它是一个整理后显示，b活动仍处于backstack，也活性的从b活动开始，所以在活动中，你应该开始用旗活动A作为

 意图launchNextActivity;
launchNextActivity =新的意图（B.class，的A.class）;
launchNextActivity.addFlags（Intent.FLAG_ACTIVITY_NEW_TASK）;
launchNextActivity.addFlags（Intent.FLAG_ACTIVITY_CLEAR_TASK）;
launchNextActivity.addFlags（Intent.FLAG_ACTIVITY_NO_ANIMATION）;
startActivity（launchNextActivity）;
 

现在你的活动，A是最高的堆栈你对backstack应用程序的任何其他活动。

现在在你想实现onBack pressed关闭应用程序的活动时，你可能会做这样的事情，

 私人布尔退出= FALSE;
@覆盖
    公共无效onBack pressed（）{
        如果（出口）{
            完（）; //完成活动
        } 其他 {
            Toast.makeText（这一点，$ P $返回再次PSS退出。
                    Toast.LENGTH_SHORT）.show（）;
            退出= TRUE;
            新的处理程序（）。postDelayed（新的Runnable（）{
                @覆盖
                公共无效的run（）{
                    退出= FALSE;
                }
            }，3 * 1000）;

        }

    }
 

该处理器在这里处理意外回到presses，它只是显示了吐司，如果有3秒钟内又回到preSS，它将关闭应用程序。

In my application i want exit from app when press back button, this my code:

@Override
    public void onBackPressed() {
        new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_alert).setTitle("Exit")
                .setMessage("Are you sure you want to exit?")
                .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {
                        finish();
                    }
                }).setNegativeButton("No", null).show();
    }

it's work correctly but when i exit from app it does not exit completely and show empty page with my app logo and when i again press back button exit from app, How can i fix it???

EDIT :

I use this code instead of above but my app exit completely but i want it running at background and does not exit completely , how can i do it?

@Override
    public void onBackPressed() {
        new AlertDialog.Builder(this).setIcon(android.R.drawable.ic_dialog_alert).setTitle("Exit")
                .setMessage("Are you sure?")
                .setPositiveButton("yes", new DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int which) {

                        Intent intent = new Intent(Intent.ACTION_MAIN);
                        intent.addCategory(Intent.CATEGORY_HOME);
                        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
                        startActivity(intent);
                        finish();
                    }
                }).setNegativeButton("no", null).show();
    } 

解决方案

When you press back and then you finish your current activity(say A), you see a blank activity with your app logo(say B), this simply means that activity B which is shown after finishing A is still in backstack, and also activity A was started from activity B, so in activity, You should start activity A with flags as

Intent launchNextActivity;
launchNextActivity = new Intent(B.class, A.class);
launchNextActivity.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
launchNextActivity.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TASK);                  
launchNextActivity.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
startActivity(launchNextActivity);

Now your activity A is top on stack with no other activities of your application on the backstack.

Now in the activity A where you want to implement onBackPressed to close the app, you may do something like this,

private Boolean exit = false;
@Override
    public void onBackPressed() {
        if (exit) {
            finish(); // finish activity
        } else {
            Toast.makeText(this, "Press Back again to Exit.",
                    Toast.LENGTH_SHORT).show();
            exit = true;
            new Handler().postDelayed(new Runnable() {
                @Override
                public void run() {
                    exit = false;
                }
            }, 3 * 1000);

        }

    }

The Handler here handles accidental back presses, it simply shows a Toast, and if there is another back press within 3 seconds, it closes the application.

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