Correct way to create Notification Channels from Android O Api

问题

The notification channels which introduced from Android O (API 26) version.I read about it from the following links:

• Managing notification channels
• Google Sample for Creating Channel

Questions:

1. If I have multiple numbers of notification then Is it a good idea to create notification channels when the application starts and keep it at ApplicationScope?

   public void addNotificationChannels(Context context) {
   
       List<NotificationChannel> channels = new ArrayList<>();
       channels.add("channel_1");
       channels.add("channel_2");
       .
       .
       channels.add("channel_7");
   
       NotificationManager notificationManager =
           (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
       notificationManager.createNotificationChannels(channels);
   
   }
   

2. What will happen if I try to execute this line new Notification.Builder(getApplicationContext(), PRIMARY_CHANNEL) before adding channels to the notification manager

回答1:

What I do, is extending the application class (don't forget to update the app's manifest with the class name) and create the notifications channels once in the onCreate method. This guarantees the notification channels are always created when building a notification.

IMHO it is a waste of CPU cycles to (try to) create the notification channels for each notification over and over again.

As a side note: I always log the app version this way too, which is quite useful when somebody sends a logcat.

回答2:

1. Ideally, you should create channel while posting notification to it. It is safe to call createNotificationChannel with same id used previously, it will not be recreated.
2. Your application won't post this notification. System might show warning toast that your app is not allowed to post this notification.

回答3:

A) At the same time you create the notification:

As the documentation says:

Creating an existing notification channel with its original values performs no operation, so it's safe to call this code when starting an app.

So you can safety create the notification channel at the same time you create the notification itself, there is no need to check if the channel is already created.

B) Inside Application or any Activity/Fragment.

Note: In case you are using raw FCM, is interesting to create the channel before the SDK publishes the notification for you because according the push payload param android_channel_id, you can associate that push to a specific channel already created in your app.

Fcm payloads: https://firebase.google.com/docs/cloud-messaging/http-server-ref

回答4:

I think there are two sensible ways:
1. Create all channels in Application subclass,
2. Create all channels in your main Activity, which first starts with the app.

来源：https://stackoverflow.com/questions/46294833/correct-way-to-create-notification-channels-from-android-o-api