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<Activity> mList = new LinkedList<Activity>();
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);
}
}

@Override
public void onLowMemory() {
super.onLowMemory();
System.gc();
}

}
在每个Activity的onCreate方法中添加类似代码：

[java] public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SysApplication.getInstance().addActivity(this);
}
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
SysApplication.getInstance().addActivity(this);
}

在需要退出程序的时候，调用：

SysApplication.getInstance().exit();
SysApplication.getInstance().exit();

简而言之，通过单例模式把每个Activity 的引用添加到一个全局链表中，每次退出程序调用System.exit(0)时，先调用链表中Activity 的finish方法

附：此方法也可参考链接：http://maosidiaoxian.iteye.com/blog/1404725

Android退出多个Activity的两个经典方法