java - 应用程序未运行时的移动后端启动器通知

Question

在我的 Android 应用程序中，我使用了 Google 的 Mobile Backend Starter。我想在服务器上的 CloudEntities 更新时收到通知，并且此通知应包含来自更新后的实体的一些数据。当应用程序在后台运行时它可以工作，但是当我关闭应用程序时(通过在多任务 View 中滑动它)，我无法发出这样的通知，因为我无法访问 CloudBackendAsync 在 GCMIntentService 中。

我已经看到这个问题了: Mobile Backend handle continuous queries in background

但是对于在GCMIntentService中访问云端数据的问题没有解决方案。

编辑:我当前在 GCMIntentService.java 中的代码

protected void onHandleIntent(Intent intent) {

    //... (Check if the GCM Message is about an update of the Mobile Backend)

            // dispatch message
            if (GCM_TYPEID_QUERY.equals(typeId)) {
                // Here, a broadcast is sent to the Main Activity of the app, which then downloads
                // the new content and shows a notification in the CloudCallbackHandler. That 
                // only works when the Activity is running.
                // So I would like to get access to the CloudBackendAsync instance from
                // the app here to download data in the background and show a notification.

                Intent messageIntent = new Intent(BROADCAST_ON_MESSAGE);
                messageIntent.putExtras(intent);
                messageIntent.putExtra("token", tokens[2]);
                LocalBroadcastManager.getInstance(this).sendBroadcast(messageIntent);
            }
    //...
}

Answer 1

Android 客户端不会通过后端的推送通知事件接收消息内容(只有 subId token 从演示后端发送，这足以通知客户端已收到给定主题的一些新消息，并且刷新它)。

据我了解，除非我们更改后端代码，否则无法在客户端 GCMIntentService.onHandleIntent() 方法中直接获取实体数据。我在后端类 ProspectiveSearchServlet 中进行了以下更改，以便它在推送通知中也包含消息内容:

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws IOException {
    // Return if push notification is not enabled
    if (!backendConfigManager.isPushEnabled()) {
      log.info("ProspectiveSearchServlet: couldn't send push notification because it is disabled.");
      return;
    }

    // dispatch GCM messages to each subscribers
    String[] subIds = req.getParameterValues("id");
    // Each subId has this format "<regId>:query:<clientSubId>"
    for (String subId : subIds) {
      String regId = SubscriptionUtility.extractRegId(subId);
      if (isSubscriptionActive(regId)) {
        Entity matchedEntity = ProspectiveSearchServiceFactory.getProspectiveSearchService().getDocument(req);
        if(matchedEntity != null) {
            log.info(String.format("ProspectiveSearchServlet: matchedEntity.toString: " + matchedEntity.toString())); 
        } else {
            log.info(String.format("ProspectiveSearchServlet: matchedEntity is null.")); 
        }
        //Add the matchedEntity object.
        sendPushNotification(regId, subId, matchedEntity);
      } else {
        SubscriptionUtility.clearSubscriptionAndDeviceEntity(Arrays.asList(regId));
      }
    }

  }

  private void sendPushNotification(String regId, String subId, Entity matchedEntity) throws IOException {
    SubscriptionUtility.MobileType type = SubscriptionUtility.getMobileType(subId);

    if (SubscriptionUtility.MobileType.ANDROID == type) {
      sendGcmAlert(subId, regId, matchedEntity);
    } else if (SubscriptionUtility.MobileType.IOS == type) {
      sendIosAlert(subId, new String[] {regId}, matchedEntity);
    }
  }


  private void sendGcmAlert(String subId, String regId, Entity matchedEntity)
      throws IOException {
    String gcmKey = backendConfigManager.getGcmKey();
    boolean isGcmKeySet = !(gcmKey == null || gcmKey.trim().length() == 0);

    // Only attempt to send GCM if GcmKey is available
    if (isGcmKeySet) {
      Sender sender = new Sender(gcmKey);

      if(matchedEntity != null) {
          Message message = new Message.Builder().addData(SubscriptionUtility.GCM_KEY_SUBID, subId)
                    //extra data.<key> elements can be added here
                    .addData("data.message", (String) matchedEntity.getProperty("message"))
                    .addData("data.updatedBy", (String) matchedEntity.getProperty("_updatedBy"))
                    .addData("data.owner", (String) matchedEntity.getProperty("_owner"))
                    .addData("data.kindName", (String) matchedEntity.getProperty("_kindName"))
                    .build();

          Result r = sender.send(message, regId, GCM_SEND_RETRIES);
          if (r.getMessageId() != null) {
            log.info("ProspectiveSearchServlet: GCM sent: subId: " + subId);
          } else {
            log.warning("ProspectiveSearchServlet: GCM error for subId: " + subId +
                ", senderId: " + gcmKey + ", error: " + r.getErrorCodeName());
            ArrayList<String> deviceIds = new ArrayList<String>();
            deviceIds.add(regId);
            SubscriptionUtility.clearSubscriptionAndDeviceEntity(deviceIds);
          }
      }  
    } else {
      // Otherwise, just write a log entry
      log.info(String.format("ProspectiveSearchServlet: GCM is not sent: GcmKey: %s ", 
          isGcmKeySet));
    }
  }

现在在客户端，您可以在 GCMIntentService 中进行以下更改以显示正确的推送通知(带有消息正文和用户名):

@Override
    protected void onHandleIntent(Intent intent) {
        Bundle extras = intent.getExtras();
        GoogleCloudMessaging gcm = GoogleCloudMessaging.getInstance(this);
        // The getMessageType() intent parameter must be the intent you received
        // in your BroadcastReceiver.
        String messageType = gcm.getMessageType(intent);

        if (!extras.isEmpty()) {  // has effect of unparcelling Bundle
            /*
             * Filter messages based on message type. Since it is likely that GCM will be
             * extended in the future with new message types, just ignore any message types you're
             * not interested in, or that you don't recognize.
             */
            if (GoogleCloudMessaging.MESSAGE_TYPE_SEND_ERROR.equals(messageType)) {
                Log.i(Consts.TAG, "onHandleIntent: message error");
            } else if (GoogleCloudMessaging.MESSAGE_TYPE_DELETED.equals(messageType)) {              
              Log.i(Consts.TAG, "onHandleIntent: message deleted");
        // If it's a regular GCM message, do some work.
        } else if (GoogleCloudMessaging.MESSAGE_TYPE_MESSAGE.equals(messageType)) {
            String subId = intent.getStringExtra(GCM_KEY_SUBID);
            Log.i(Consts.TAG, "onHandleIntent: subId: " + subId);
            String[] tokens = subId.split(":");
            String typeId = tokens[1];

            // dispatch message
            if (GCM_TYPEID_QUERY.equals(typeId)) {
                Intent messageIntent = new Intent(BROADCAST_ON_MESSAGE);
                messageIntent.putExtras(intent);
                messageIntent.putExtra("token", tokens[2]);
                boolean isReceived = LocalBroadcastManager.getInstance(this).sendBroadcast(messageIntent);
                //Check if the broadcast has been handled, if not show the notification.
                if (!isReceived) {
                    Log.i(Consts.TAG, "A message has been recieved but no broadcast was handled.");
                    generateNotification(this, intent, tokens[2]);
                } else {
                    Log.i(Consts.TAG, "A message has been recieved, broadcasted and handled.");
                }
            }
        }
    }
    // Release the wake lock provided by the WakefulBroadcastReceiver.
    GCMBroadcastReceiver.completeWakefulIntent(intent);
}

public static void generateNotification(Context context, Intent intent, String message) {
    //Event keys
    HashMap data = new HashMap();
    for (String key : intent.getExtras().keySet()) {
        Log.d(Consts.TAG, "Message key: " + key + " value: " + intent.getExtras().getString(key));
        String eventKey = key.startsWith("data.") ? key.substring(5) : key;
        data.put(eventKey, intent.getExtras().getString(key));
    }

    CharSequence contentTitle = (CharSequence) data.get("updatedBy");
    if (contentTitle == null) contentTitle = "New Message";

    CharSequence contentText = (CharSequence) data.get("message");
    if (contentText == null) contentText = "";

    CharSequence userId = (CharSequence) data.get("updatedBy");
    Bitmap iconBitmap = getUserIcon(context, userId.toString());
    if (iconBitmap == null) iconBitmap = BitmapFactory.decodeResource(context.getResources(), R.drawable.ic_launcher);

    // Creates an Intent for the Activity
    Intent resultIntent = new Intent(context, GuestbookActivity.class);
    // The stack builder object will contain an artificial back stack for the started Activity.
    // This ensures that navigating backward from the Activity leads out of
    // your application to the Home screen.
    TaskStackBuilder stackBuilder = TaskStackBuilder.create(context);
    // Adds the back stack for the Intent (but not the Intent itself)
    stackBuilder.addParentStack(IntroductionActivity.class);
    // Adds the Intent that starts the Activity to the top of the stack
    stackBuilder.addNextIntent(resultIntent);
    PendingIntent resultPendingIntent = stackBuilder.getPendingIntent(0, PendingIntent.FLAG_UPDATE_CURRENT);


    Notification.Builder mBuilder = new Notification.Builder(context);
    mBuilder.setContentIntent(resultPendingIntent);

    Notification notification = mBuilder
    .setContentTitle(contentTitle)
    .setContentText(contentText)
    .setSmallIcon(R.drawable.notification_icon)
    .setLargeIcon(iconBitmap)
    .setTicker(contentTitle + ": " + contentText)
    .setWhen(System.currentTimeMillis())
    .setAutoCancel(true)
    .build();

    ///Get the notification ID, /it allows to update the notification later on.
    int notifyID = 1;
    String contentID = (String) data.get("id");
    if(contentID != null) {
        notifyID = Integer.parseInt(contentID);
    }

    NotificationManager mNotificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
    mNotificationManager.notify(notifyID, notification);
}