notification中发起activity问题

String ns = Context.NOTIFICATION_SERVICE; 
    NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns); 
    int icon = R.drawable.icon;      
    long when = System.currentTimeMillis(); 
    Notification notification = new Notification(icon, "Test Notification", when); 
 
 
    Context context = getApplicationContext();       
 
    Bundle bundle = new Bundle(); 
    bundle.putString("action", "view"); 
    Intent notificationIntent = new Intent(this, MainActivity.class); 
    notificationIntent.putExtras(bundle); 
 
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, Intent.FLAG_ACTIVITY_NEW_TASK); 
    notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent);      
    mNotificationManager.notify(1, notification);

下面是要取出"action", 的值

Bundle bundle = this.getIntent().getExtras(); 
 
    if(bundle != null) 
    { String action = bundle.getString("action"); 
            performAction(action) 
    }

程序呢按照预期执行，只是当我返回程序，把状态栏缩小，然后回到屏幕通过程序的图标发起程序竟然从上次notivication点击的时候发起，

可以通过

Intent intent = getIntent(); 
int flags = intent.getFlags(); 
boolean launchedFromHistory = ((flags & Intent.FLAG_ACTIVITY_LAUNCHED_FROM_HISTORY)

来判断一下是不是从历史中发起的