我这就一个APP尝试Notification设置，具体就不说了，也忘了从哪儿参考的了。直接把代码贴出来，按需修改。

    //    创建渠道
    private String createNotificationChannel(String channelID, String channelNAME, int level) {
        if (android.os.Build.VERSION.SDK_INT >= android.os.Build.VERSION_CODES.O) {
            NotificationManager manager = (NotificationManager) getSystemService(NOTIFICATION_SERVICE);
            NotificationChannel channel = new NotificationChannel(channelID, channelNAME, level);
            manager.createNotificationChannel(channel);
            return channelID;
        } else {
            return null;
        }
    }

    private void showNotification(String Information){
        Intent intent = new Intent(this,  MainActivity.class);
        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);

        PendingIntent pendingIntent = PendingIntent.getActivity(this, 0, intent, 0);
        String channelId = createNotificationChannel("my_channel_ID", "my_channel_NAME", NotificationManager.IMPORTANCE_HIGH);
        NotificationCompat.Builder notification = new NotificationCompat.Builder(this, channelId)
                .setContentTitle("History")
                .setContentText(Information)
                .setContentIntent(pendingIntent)
                .setSmallIcon(R.drawable.logo_small)
                .setPriority(NotificationCompat.PRIORITY_HIGH)
                .setAutoCancel(true)
                .addAction(R.drawable.round_bt, getString(R.string.notifytext),
                        pendingIntent);
        NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
        notificationManager.notify(100, notification.build());
    }

参考

• 通知概览 | Android开发者