如何随时退出程序

背景：如果手机界面停留在ThirdActivity，你会发现当前想退出程序，需要按3次BACK键.按Home键只是暂时将程序挂起。如果我们想只按一下就能退出程序该怎么办？

步骤：

1：写一个类BaseActivity 继承Activity

2:写一个集合类ActivityCollector ，写3个方法，addActivity,removeActivity,finishAll

3:在类MyActivity里面调用该集合里面的方法，需要销毁的Activity调用finishAll

代码如下:

public class BaseActivity extends Activity{
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        Log.d("BaseActivity",getClass().getSimpleName());
        ActivityCollector.addActivity(this);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        ActivityCollector.removeActivity(this);
    }
}

public class ActivityCollector {
    public static List<Activity>activities = new ArrayList<>();
    public static void addActivity(Activity activity){
        activities.add(activity);
    }
    public static void removeActivity(Activity activity){
        activities.remove(activity);
    }
    public static void finnishAll(){//将list中存储的活动全部销毁
        for (Activity activity:activities) {
            if(!activity.isFinishing()){//isFinishing()判断当前activity是否被干掉了   true：被干掉了，false：还没被干掉
                activity.finish();
            }
        }
    }
}