在Oreo SDK之后，你必须创建通知通道才能显示通知，请查看以下方法以供参考：

/**
 *
 * @param context
 * @param title  --> title to show
 * @param message --> details to show
 * @param intent --> What should happen on clicking the notification
 * @param reqCode --> unique code for the notification
 */

public void showNotification(Context context, String title, String message, Intent intent, int reqCode) {
    SharedPreferenceManager sharedPreferenceManager = SharedPreferenceManager.getInstance(context);

    PendingIntent pendingIntent = PendingIntent.getActivity(context, reqCode, intent, PendingIntent.FLAG_ONE_SHOT);
    String CHANNEL_ID = "channel_name";// The id of the channel.
    NotificationCompat.Builder notificationBuilder = new NotificationCompat.Builder(context, CHANNEL_ID)
            .setSmallIcon(R.mipmap.notification_logo)
            .setContentTitle(title)
            .setContentText(message)
            .setAutoCancel(true)
            .setSound(RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION))
            .setContentIntent(pendingIntent);
    NotificationManager notificationManager = (NotificationManager) context.getSystemService(Context.NOTIFICATION_SERVICE);
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
        CharSequence name = "Channel Name";// The user-visible name of the channel.
        int importance = NotificationManager.IMPORTANCE_HIGH;
        NotificationChannel mChannel = new NotificationChannel(CHANNEL_ID, name, importance);
        notificationManager.createNotificationChannel(mChannel);
    }
    notificationManager.notify(reqCode, notificationBuilder.build()); // 0 is the request code, it should be unique id

    Log.d("showNotification", "showNotification: " + reqCode);
}

如何使用此方法：

int reqCode = 1;
    Intent intent = new Intent(getApplicationContext(), MainActivity.class);
    showNotification(this, "Title", "This is the message to display", intent, reqCode);

public void sendNotification (String message, String title ){

        Intent intent = new Intent(getApplicationContext(), CampaignActivity.class);
        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0 , intent,
                PendingIntent.FLAG_IMMUTABLE);

        String channelId = "some_channel_id";
        Uri defaultSoundUri = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);
        NotificationCompat.Builder notificationBuilder =
                new NotificationCompat.Builder(this, channelId)
                        .setSmallIcon(R.mipmap.ic_launcher_round)
//                        .setContentTitle(getString(R.string.app_name)
                        .setContentTitle(title)
                        .setContentText(message)
                        .setAutoCancel(true)
                        .setSound(defaultSoundUri)
                        .setContentIntent(pendingIntent);

        NotificationManager notificationManager =
                (NotificationManager) getSystemService(Context.NOTIFICATION_SERVICE);

        // Since android Oreo notification channel is needed.
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
            NotificationChannel channel = new NotificationChannel(channelId,
                    "Channel human readable title",
                    NotificationManager.IMPORTANCE_DEFAULT);
            assert notificationManager != null;
            notificationManager.createNotificationChannel(channel);
        }

        assert notificationManager != null;
        notificationManager.notify(0 /* ID of notification */, notificationBuilder.build());
    }