FCM升级后，通知未显示在Android API级别26+上

Question

The code below doesn't seem to be showing a notification on my emulator. I upgraded from the deprecated Firebase code to the new stuff, with channels. Is there something I should look into?

<application android:icon="@drawable/icon" android:allowBackup="false" android:label="@string/application_label" android:theme="@style/Theme">
        <meta-data android:name="com.google.firebase.messaging.default_notification_icon" android:resource="@drawable/icon" />
        <meta-data android:name="com.google.firebase.messaging.default_notification_color" android:resource="@color/accentColor" />
        <meta-data android:name="com.google.firebase.messaging.default_notification_channel_id" android:value="@string/default_notification_channel_id" />
        ......
        <service
            android:name="com.exposure.services.ExposureFirebaseMessagingService">
            <intent-filter>
                <action android:name="com.google.firebase.MESSAGING_EVENT"/>
            </intent-filter>
        </service>
    </application>

Answer 1

From Android Oreo, you must use channels to create notifications.

Starting in Android 8.0 (API level 26), all notifications must be assigned to a channel. For each channel, you can set the visual and auditory behavior that is applied to all notifications in that channel. Then, users can change these settings and decide which notification channels from your app should be intrusive or visible at all.

---

Caution: If you target Android 8.0 (API level 26) and post a notification without specifying a notification channel, the notification does not appear and the system logs an error.

Read more docs at: https://developer.android.com/training/notify-user/channels

---

Apparently, you have used a notification channel for your notifications, but haven't created a notification channel associated with that id. So you will need to create a notification channel before creating notifications.

Example to create a notification channel (maybe in your FCM Service class) is given below:

@Override
public void onCreate() {
    super.onCreate();
    if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
        // Make sure you use the same channel id ("default" in this case)
        // while creating notifications.
        NotificationChannel channel = new NotificationChannel("default", "Default Channel",
                NotificationManager.IMPORTANCE_HIGH);
        channel.setDescription("Default Notification Channel");
        NotificationManager notificationManager = (NotificationManager)
                getSystemService(NOTIFICATION_SERVICE);
        if (notificationManager != null) {
            notificationManager.createNotificationChannel(channel);
        }
    }
}

Answer 2

在根据Google开发者方https://developer.android.com/training/notify-user/channels创建通知之前，请使用通知频道