Android中的Notification机制深入理解

NotificationCompat.Builder mBuilder =
  new NotificationCompat.Builder(this)
  .setSmallIcon(R.drawable.notification_icon)
  .setWhen(System.currentTimeMillis())
  .setContentTitle("Test Notification Title")
  .setContentText("Test Notification Content!");
Intent resultIntent = new Intent(this, ResultActivity.class);

PendingIntent contentIntent =
  PendingIntent.getActivity(
   this, 
   0, 
   resultIntent, 
   PendingIntent.FLAG_UPDATE_CURRENT
  );
mBuilder.setContentIntent(resultPendingIntent);
NotificationManager mNotificationManager =
 (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);
// mId allows you to update the notification later on.
mNotificationManager.notify(mId, mBuilder.build());

public void notify(int id, Notification notification)
{
 notify(null, id, notification);
}

// 省略部分注释
public void notify(String tag, int id, Notification notification)
{
 notifyAsUser(tag, id, notification, new UserHandle(UserHandle.myUserId()));
}

/**
 * @hide
 */
public void notifyAsUser(String tag, int id, Notification notification, UserHandle user)
{
 int[] idOut = new int[1];
 INotificationManager service = getService();
 String pkg = mContext.getPackageName();
 // Fix the notification as best we can.
 Notification.addFieldsFromContext(mContext, notification);
 if (notification.sound != null) {
  notification.sound = notification.sound.getCanonicalUri();
  if (StrictMode.vmFileUriExposureEnabled()) {
   notification.sound.checkFileUriExposed("Notification.sound");
  }
 }
 fixLegacySmallIcon(notification, pkg);
 if (mContext.getApplicationInfo().targetSdkVersion > Build.VERSION_CODES.LOLLIPOP_MR1) {
  if (notification.getSmallIcon() == null) {
   throw new IllegalArgumentException("Invalid notification (no valid small icon): "
     + notification);
  }
 }
 if (localLOGV) Log.v(TAG, pkg + ": notify(" + id + ", " + notification + ")");
 final Notification copy = Builder.maybeCloneStrippedForDelivery(notification);
 try {
  // !!!
  service.enqueueNotificationWithTag(pkg, mContext.getOpPackageName(), tag, id,
    copy, idOut, user.getIdentifier());
  if (localLOGV && id != idOut[0]) {
   Log.v(TAG, "notify: id corrupted: sent " + id + ", got back " + idOut[0]);
  }
 } catch (RemoteException e) {
  throw e.rethrowFromSystemServer();
 }
}

@Override
public void enqueueNotificationWithTag(String pkg, String opPkg, String tag, int id,
   Notification notification, int[] idOut, int userId) throws RemoteException {
 enqueueNotificationInternal(pkg, opPkg, Binder.getCallingUid(),
   Binder.getCallingPid(), tag, id, notification, idOut, userId);
}

void enqueueNotificationInternal(final String pkg, final String opPkg, final int callingUid,
  final int callingPid, final String tag, final int id, final Notification notification,
  int[] idOut, int incomingUserId) {
 if (DBG) {
  Slog.v(TAG, "enqueueNotificationInternal: pkg=" + pkg + " id=" + id
    + " notification=" + notification);
 }
 checkCallerIsSystemOrSameApp(pkg);
 final boolean isSystemNotification = isUidSystem(callingUid) || ("android".equals(pkg));
 final boolean isNotificationFromListener = mListeners.isListenerPackage(pkg);

 final int userId = ActivityManager.handleIncomingUser(callingPid,
   callingUid, incomingUserId, true, false, "enqueueNotification", pkg);
 final UserHandle user = new UserHandle(userId);

 // Fix the notification as best we can.
 try {
  final ApplicationInfo ai = getContext().getPackageManager().getApplicationInfoAsUser(
    pkg, PackageManager.MATCH_DEBUG_TRIAGED_MISSING,
    (userId == UserHandle.USER_ALL) ? UserHandle.USER_SYSTEM : userId);
  Notification.addFieldsFromContext(ai, userId, notification);
 } catch (NameNotFoundException e) {
  Slog.e(TAG, "Cannot create a context for sending app", e);
  return;
 }

 mUsageStats.registerEnqueuedByApp(pkg);

 if (pkg == null || notification == null) {
  throw new IllegalArgumentException("null not allowed: pkg=" + pkg
    + " id=" + id + " notification=" + notification);
 }
 final StatusBarNotification n = new StatusBarNotification(
   pkg, opPkg, id, tag, callingUid, callingPid, 0, notification,
   user);

 // Limit the number of notifications that any given package except the android
 // package or a registered listener can enqueue. Prevents DOS attacks and deals with leaks.
 if (!isSystemNotification && !isNotificationFromListener) {
  synchronized (mNotificationList) {
   if(mNotificationsByKey.get(n.getKey()) != null) {
    // this is an update, rate limit updates only
    final float appEnqueueRate = mUsageStats.getAppEnqueueRate(pkg);
    if (appEnqueueRate > mMaxPackageEnqueueRate) {
     mUsageStats.registerOverRateQuota(pkg);
     final long now = SystemClock.elapsedRealtime();
     if ((now - mLastOverRateLogTime) > MIN_PACKAGE_OVERRATE_LOG_INTERVAL) {
      Slog.e(TAG, "Package enqueue rate is " + appEnqueueRate
        + ". Shedding events. package=" + pkg);
       mLastOverRateLogTime = now;
     }
     return;
    }
   }

   int count = 0;
   final int N = mNotificationList.size();
   for (int i=0; i<N; i++) {
    final NotificationRecord r = mNotificationList.get(i);
    if (r.sbn.getPackageName().equals(pkg) && r.sbn.getUserId() == userId) {
     if (r.sbn.getId() == id && TextUtils.equals(r.sbn.getTag(), tag)) {
      break; // Allow updating existing notification
     }
     count++;
     if (count >= MAX_PACKAGE_NOTIFICATIONS) {
      mUsageStats.registerOverCountQuota(pkg);
      Slog.e(TAG, "Package has already posted " + count
        + " notifications. Not showing more. package=" + pkg);
      return;
     }
    }
   }
  }
 }

 // Whitelist pending intents.
 if (notification.allPendingIntents != null) {
  final int intentCount = notification.allPendingIntents.size();
  if (intentCount > 0) {
   final ActivityManagerInternal am = LocalServices
     .getService(ActivityManagerInternal.class);
   final long duration = LocalServices.getService(
     DeviceIdleController.LocalService.class).getNotificationWhitelistDuration();
   for (int i = 0; i < intentCount; i++) {
    PendingIntent pendingIntent = notification.allPendingIntents.valueAt(i);
    if (pendingIntent != null) {
     am.setPendingIntentWhitelistDuration(pendingIntent.getTarget(), duration);
    }
   }
  }
 }

 // Sanitize inputs
 notification.priority = clamp(notification.priority, Notification.PRIORITY_MIN,
   Notification.PRIORITY_MAX);

 // setup local book-keeping
 final NotificationRecord r = new NotificationRecord(getContext(), n);
 mHandler.post(new EnqueueNotificationRunnable(userId, r));

 idOut[0] = id;
}

@Override
public void run() {
 synchronized(mNotificationList) {
  // 省略代码
  if (notification.getSmallIcon() != null) {
   StatusBarNotification oldSbn = (old != null) ? old.sbn : null;
   mListeners.notifyPostedLocked(n, oldSbn);
  } else {
   Slog.e(TAG, "Not posting notification without small icon: " + notification);
   if (old != null && !old.isCanceled) {
    mListeners.notifyRemovedLocked(n);
   }
   // ATTENTION: in a future release we will bail out here
   // so that we do not play sounds, show lights, etc. for invalid
   // notifications
   Slog.e(TAG, "WARNING: In a future release this will crash the app: " + n.getPackageName());
  }
  buzzBeepBlinkLocked(r);
 }
}

public void notifyPostedLocked(StatusBarNotification sbn, StatusBarNotification oldSbn) {
 // Lazily initialized snapshots of the notification.
 TrimCache trimCache = new TrimCache(sbn);
 for (final ManagedServiceInfo info: mServices) {
  boolean sbnVisible = isVisibleToListener(sbn, info);
  boolean oldSbnVisible = oldSbn != null ? isVisibleToListener(oldSbn, info) : false;
  // This notification hasn't been and still isn't visible -> ignore.
  if (!oldSbnVisible && !sbnVisible) {
   continue;
  }
  final NotificationRankingUpdate update = makeRankingUpdateLocked(info);
  // This notification became invisible -> remove the old one.
  if (oldSbnVisible && !sbnVisible) {
   final StatusBarNotification oldSbnLightClone = oldSbn.cloneLight();
   mHandler.post(new Runnable() {
    @Override
    public void run() {
     notifyRemoved(info, oldSbnLightClone, update);
    }
   });
   continue;
  }
  final StatusBarNotification sbnToPost = trimCache.ForListener(info);
  mHandler.post(new Runnable() {
   @Override
   public void run() {
    notifyPosted(info, sbnToPost, update);
   }
  });
 }
}

private void notifyPosted(final ManagedServiceInfo info, final StatusBarNotification sbn, NotificationRankingUpdate rankingUpdate) {
 final INotificationListener listener = (INotificationListener) info.service;
 StatusBarNotificationHolder sbnHolder = new StatusBarNotificationHolder(sbn);
 try {
  listener.onNotificationPosted(sbnHolder, rankingUpdate);
 } catch (RemoteException ex) {
  Log.e(TAG, "unable to notify listener (posted): " + listener, ex);
 }
}

public void onNotificationPosted(IStatusBarNotificationHolder sbnHolder, NotificationRankingUpdate update) {
 StatusBarNotification sbn;
 try {
  sbn = sbnHolder.get();
 } catch (RemoteException e) {
  Log.w(TAG, "onNotificationPosted: Error receiving StatusBarNotification", e);
  return;
 }
 try {
  // convert icon metadata to legacy format for older clients
  createLegacyIconExtras(sbn.getNotification());
  maybePopulateRemoteViews(sbn.getNotification());
 } catch (IllegalArgumentException e) {
  // warn and drop corrupt notification
  Log.w(TAG, "onNotificationPosted: can't rebuild notification from " + sbn.getPackageName());
  sbn = null;
 }
 // protect subclass from concurrent modifications of (@link mNotificationKeys}.
 synchronized(mLock) {
  applyUpdateLocked(update);
  if (sbn != null) {
   SomeArgs args = SomeArgs.obtain();
   args.arg1 = sbn;
   args.arg2 = mRankingMap;
   mHandler.obtainMessage(MyHandler.MSG_ON_NOTIFICATION_POSTED, args).sendToTarget();
  } else {
   // still pass along the ranking map, it may contain other information
   mHandler.obtainMessage(MyHandler.MSG_ON_NOTIFICATION_RANKING_UPDATE, mRankingMap).sendToTarget();
  }
 }
}

public void start() {
 // 省略代码
 // Set up the initial notification state.
 try {
  mNotificationListener.registerAsSystemService(mContext,
    new ComponentName(mContext.getPackageName(), getClass().getCanonicalName()),
    UserHandle.USER_ALL);
 } catch (RemoteException e) {
  Log.e(TAG, "Unable to register notification listener", e);
 }
 // 省略代码
}

public void registerAsSystemService(Context context, ComponentName componentName,
  int currentUser) throws RemoteException {
 if (mWrapper == null) {
  mWrapper = new NotificationListenerWrapper();
 }
 mSystemContext = context;
 INotificationManager noMan = getNotificationInterface();
 mHandler = new MyHandler(context.getMainLooper());
 mCurrentUser = currentUser;
 noMan.registerListener(mWrapper, componentName, currentUser);
}

private final NotificationListenerService mNotificationListener = new NotificationListenerService() {
 // 省略代码
 
 @Override
 public void onNotificationPosted(final StatusBarNotification sbn, final RankingMap rankingMap) {
  if (DEBUG) Log.d(TAG, "onNotificationPosted: " + sbn);
  if (sbn != null) {
   mHandler.post(new Runnable() {
    @Override
    public void run() {
     processForRemoteInput(sbn.getNotification());
     String key = sbn.getKey();
     mKeysKeptForRemoteInput.remove(key);
     boolean isUpdate = mNotificationData.get(key) != null;
     // In case we don't allow child notifications, we ignore children of
     // notifications that have a summary, since we're not going to show them
     // anyway. This is true also when the summary is canceled,
     // because children are automatically canceled by NoMan in that case.
     if (!ENABLE_CHILD_NOTIFICATIONS && mGroupManager.isChildInGroupWithSummary(sbn)) {
      if (DEBUG) {
       Log.d(TAG, "Ignoring group child due to existing summary: " + sbn);
      }
      // Remove existing notification to avoid stale data.
      if (isUpdate) {
       removeNotification(key, rankingMap);
      } else {
       mNotificationData.updateRanking(rankingMap);
      }
      return;
     }
     if (isUpdate) {
      updateNotification(sbn, rankingMap);
     } else {
      addNotification(sbn, rankingMap, null /* oldEntry */ );
     }
    }
   });
  }
 }
 // 省略代码
}

@Override
public void addNotification(StatusBarNotification notification, RankingMap ranking, Entry oldEntry) {
 if (DEBUG) Log.d(TAG, "addNotification key=" + notification.getKey());
 mNotificationData.updateRanking(ranking);
 Entry shadeEntry = createNotificationViews(notification);
 if (shadeEntry == null) {
  return;
 }
 boolean isHeadsUped = shouldPeek(shadeEntry);
 if (isHeadsUped) {
  mHeadsUpManager.showNotification(shadeEntry);
  // Mark as seen immediately
  setNotificationShown(notification);
 }
 if (!isHeadsUped && notification.getNotification().fullScreenIntent != null) {
  if (shouldSuppressFullScreenIntent(notification.getKey())) {
   if (DEBUG) {
    Log.d(TAG, "No Fullscreen intent: suppressed by DND: " + notification.getKey());
   }
  } else if (mNotificationData.getImportance(notification.getKey()) < NotificationListenerService.Ranking.IMPORTANCE_MAX) {
   if (DEBUG) {
    Log.d(TAG, "No Fullscreen intent: not important enough: " + notification.getKey());
   }
  } else {
   // Stop screensaver if the notification has a full-screen intent.
   // (like an incoming phone call)
   awakenDreams();
   // not immersive & a full-screen alert should be shown
   if (DEBUG) Log.d(TAG, "Notification has fullScreenIntent; sending fullScreenIntent");
   try {
    EventLog.writeEvent(EventLogTags.SYSUI_FULLSCREEN_NOTIFICATION, notification.getKey());
    notification.getNotification().fullScreenIntent.send();
    shadeEntry.notifyFullScreenIntentLaunched();
    MetricsLogger.count(mContext, "note_fullscreen", 1);
   } catch (PendingIntent.CanceledException e) {}
  }
 }
 // !!!
 addNotificationViews(shadeEntry, ranking);
 // Recalculate the position of the sliding windows and the titles.
 setAreThereNotifications();
}