通知不起作用- Android Studio

<uses-permission android:name="android.permission.POST_NOTIFICATIONS"/>

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O) {
    NotificationChannel channel = new NotificationChannel("channel_id", "Channel Name", NotificationManager.IMPORTANCE_DEFAULT);
    NotificationManager manager = getSystemService(NotificationManager.class);
    manager.createNotificationChannel(channel);
}

NotificationCompat.Builder builder = new NotificationCompat.Builder(this, "channel_id")
        .setSmallIcon(R.drawable.ic_notification)
        .setContentTitle("Notification Title")
        .setContentText("Notification Content")
        .setPriority(NotificationCompat.PRIORITY_DEFAULT);

NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
notificationManager.notify(1, builder.build());