PendingIntent的flag和原理解析
| flag | 含义 |
| PendingIntent.FLAG_CANCEL_CURRENT | 如果PendingIntent已经存在，则取消当前的PendingIntent，重新创建一个新的PendingIntent。 |
| PendingIntent.FLAG_NO_CREATE | 如果PendingIntent已经存在，则返回null，而不是重新创建一个新的PendingIntent。 |
| PendingIntent.FLAG_ONE_SHOT | 只能使用一次，使用后会自动取消。 |
| PendingIntent.FLAG_UPDATE_CURRENT | 如果PendingIntent已经存在，则更新当前的PendingIntent。 |
| PendingIntent.FLAG_IMMUTABLE | 表示创建的PendingIntent应该是不可变的？？？ |
| PendingIntent.FLAG_MUTABLE | 表示创建的PendingIntent应该是可变的？？？ |
PendingIntentController的getIntentSender方法中
final boolean noCreate = (flags & PendingIntent.FLAG_NO_CREATE) != 0;
final boolean cancelCurrent = (flags & PendingIntent.FLAG_CANCEL_CURRENT) != 0;
final boolean updateCurrent = (flags & PendingIntent.FLAG_UPDATE_CURRENT) != 0;
flags &= ~(PendingIntent.FLAG_NO_CREATE | PendingIntent.FLAG_CANCEL_CURRENT| PendingIntent.FLAG_UPDATE_CURRENT);PendingIntentRecord.Key key = new PendingIntentRecord.Key(type, packageName, featureId,token, resultWho, requestCode, intents, resolvedTypes, flags,new SafeActivityOptions(opts), userId);
WeakReference<PendingIntentRecord> ref;
ref = mIntentSenderRecords.get(key);
PendingIntentRecord rec = ref != null ? ref.get() : null;
if (rec != null) {if (!cancelCurrent) {if (updateCurrent) {// FLAG_UPDATE_CURRENT标签，则更新当前的pendingIntentif (rec.key.requestIntent != null) {rec.key.requestIntent.replaceExtras(intents != null ?intents[intents.length - 1] : null);}if (intents != null) {intents[intents.length - 1] = rec.key.requestIntent;rec.key.allIntents = intents;rec.key.allResolvedTypes = resolvedTypes;} else {rec.key.allIntents = null;rec.key.allResolvedTypes = null;}}return rec;}// FLAG_CANCEL_CURRENT则先把当前的cancel掉，再重新创建一个pendingIntentmakeIntentSenderCanceled(rec, CANCEL_REASON_SUPERSEDED);mIntentSenderRecords.remove(key);decrementUidStatLocked(rec);
}
if (noCreate) {// FLAG_NO_CREATE 则直接返回当前的pendingIntentreturn rec;
}
// 重新创建一个新的
rec = new PendingIntentRecord(this, key, callingUid);在PendingIntentRecord的sendInner中
if ((key.flags & PendingIntent.FLAG_ONE_SHOT) != 0) {// 如果是PendingIntent.FLAG_ONE_SHOT，则发送完就立刻cancel掉controller.cancelIntentSender(this, true, CANCEL_REASON_ONE_SHOT_SENT);
}