Android实现再按一次(返回键)实现退出(应用程序)

1、定义一个继承自Application的ExitApplication类

package com.example.weather;import android.app.Activity;import android.app.Application;import java.util.ArrayList;import java.util.List;public class ExitApplication extends Application {    private List activityList = new ArrayList<>();    private static ExitApplication instance;    public static ExitApplication getInstance(){        if(null == instance){            instance = new ExitApplication();        }        return instance;    }    //添加Activity到容器中    public void addActivity(Activity activity){        //Log.i("activity", "size:" + activityList.size());        //Log.i("activity", "name:" + activity.getIntent());        activityList.add(activity);    }    //遍历所有Activity并finish    public void exit(){        for(Activity activity : activityList){            //依次关闭            activity.finish();            //Log.i("activity", "del_size:" + activityList.size());            //Log.i("activity", "del_name:" + activity.getIntent());        }        //强制退出        System.exit(0);    }}

2、定义一个时间

private long exitTime;

3、在启动Activity中添加初始时间

exitTime=System.currentTimeMillis();

4、在每个Activity的onCreate()中添加这一句

ExitApplication.getInstance().addActivity(MainActivity.this);

5、在需要“再按一次(返回键)实现退出(应用程序)”的Activity中重写onBackPressed()方法

@Override    public void onBackPressed() {        if ((System.currentTimeMillis() - exitTime) > 2000) {            Toast.makeText(getApplicationContext(), "再按一次退出程序", Toast.LENGTH_SHORT).show();            exitTime = System.currentTimeMillis();        }        else{            ExitApplication.getInstance().exit();        }    }

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