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();
        }
    }