Android PendingIntent中放置Extra值問題

.....(略)
 Intent it=  new Intent(this , MyActivity.class);
 it.putExtra("myFlag", dynamicFlag);

PendingIntent pit= PendingIntent.getActivity(this, 0, it, 0);
 remoteViews.setOnClickPendingIntent(R.id.btnMyButton, pit);
....(略)

上列是我在寫AppWidget時的程式片段，這段程式主要是要在App Widget上的按鈕按下時,開啟某Actitity(並傳遞myFlag extra值給該Activity)以顯示所需資訊，但當我在MyActivity取得myFlag值時卻一直都是0,百思不解，後來修改程式，將PendingIntent.getActitity的最後個參數換成:
PendingIntent pit= PendingIntent.getActivity(this, 0, it, PendingIntent.FLAG_UPDATE_CURRENT);後竟然就正常了～

關於該參數該使用那個FLAG請參考：
http://developer.android.com/reference/android/app/PendingIntent.html#getActivity(android.content.Context, int, android.content.Intent, int)

http://stackoverflow.com/questions/4472447/confusing-behavior-when-starting-new-activity-with-pendingintent/5013713#5013713