Android 退出整个程序代码

今天在网上看见个博客关于退出整个程序的，感觉不错，拿来分享学习

SysApplication这个类复制到工程里面，然后在每个Acitivity的oncreate方法里面通过SysApplication.getInstance().addActivity(this); 添加当前Acitivity到ancivitylist里面去，最后在想退出的时候调用SysApplication.getInstance().exit();可直接关闭所有的Acitivity并退出应用程序。

import java.util.LinkedList; 
import java.util.List; 
import android.app.Activity; 
import android.app.AlertDialog; 
import android.app.Application; 
import android.content.DialogInterface; 
import android.content.Intent; 

public class SysApplication extends Application { 
    private List mList = new LinkedList(); 
    private static SysApplication instance; 

    private SysApplication() {   
     } 
    public synchronized static SysApplication getInstance() { 
        if (null == instance) { 
            instance = new SysApplication(); 
        } 
        return instance; 
    } 
    // add Activity  
     public void addActivity(Activity activity) { 
        mList.add(activity); 
    } 

    public void exit() { 
        try { 
            for (Activity activity : mList) { 
                if (activity != null) 
                    activity.finish(); 
            } 
        } catch (Exception e) { 
            e.printStackTrace(); 
        } finally { 
            System.exit(0); 
        } 
    } 
    public void onLowMemory() { 
        super.onLowMemory();     
         System.gc(); 
    }  
 }

public void onCreate(Bundle savedInstanceState)
 {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.main);
 SysApplication.getInstance().addActivity(this); 
}