How to change the notification settings in android apps?

How can I switch all these settings on programmatically?

I noticed when you install WhatsApp they are all switched on in the beginning(look at the image below).

But I can not find a way to turn them on programmatically.

Here is how I send notifications:

 private void sendNotification(Intent intent){

    Context context = NotificationService.this;

    //open the activity after the notification is clicked
    Intent intent1 = new Intent(getApplicationContext(),MainActivity.class);

    PendingIntent pIntent = PendingIntent.getActivity(context, 0, intent1, 0);


    Notification.Builder builder = new Notification.Builder(context)
            .setTicker("Notification")
            .setContentTitle("Important Message")
            .setContentText("This is an example of a push notification using a Navigation Manager")
            .setSmallIcon(R.drawable.ic_add)
            .setContentIntent(pIntent);



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

    Uri alarmSound = RingtoneManager.getDefaultUri(RingtoneManager.TYPE_NOTIFICATION);

    //These are necessary for the notification to pop up
    if(Build.VERSION.SDK_INT < Build.VERSION_CODES.O){

        builder.setPriority(Notification.PRIORITY_MAX);
        builder.setSound(alarmSound);
        builder.setLights(Color.BLUE, 500, 500);
    }

    //after android O we must use notification channels
    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O)
    {
        String channelId = "Your_channel_id";
        NotificationChannel channel = new NotificationChannel(
                channelId,
                "Reminder to remind to review your notes",
                NotificationManager.IMPORTANCE_HIGH);

        if(alarmSound != null){
            AudioAttributes att = new AudioAttributes.Builder()
                    .setUsage(AudioAttributes.USAGE_NOTIFICATION)
                    .setContentType(AudioAttributes.CONTENT_TYPE_SONIFICATION)
                    .build();

            channel.setSound(alarmSound,att);
        }


        channel.setLightColor(Color.BLUE);
        channel.enableVibration(true);
        channel.setDescription("Hello Dear friends"); //this is to test what this is

        channel.setLockscreenVisibility(Notification.VISIBILITY_PUBLIC);

        channel.setVibrationPattern(new long[]{300, 300, 300});
        notificationManager.createNotificationChannel(channel);
        builder.setChannelId(channelId);
    }


    Notification notification = builder.build();
    notificationManager.notify(0, notification);


}

I also added this permission to manifest:

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

Update:
Using this code on the emulator, I get the heads-up notification. But on my Xiaomi device, there is no heads-up notification. It just appears on the status bar. If I manually turn on the floating notification (which you can see in the photo) then I will get heads-up notification. But they are switched off by default. When you install Whatsapp they are all switched on.
Is that a kind of privilege for Whatsapp as it is famout? or is there a way to do it?

By default, when you install a app, the system register's default notification channel (on low priority) that doesn't support head up notification by default, it's turned off. You can't control that.

But what you can do it create your own notification channel with highest priority and then register it on app run once.

After that just pass the channel Id with your notification builder so that system shows the head's up notification which you want.

More information can be found here https://developer.android.com/training/notify-user/channels

I have tried for this but unable to set these settings programmatically. Instead of this I have used following method to open notification settings screen to enable notification sounds/vibration.

 private void openNotificationSettingsForApp(String channelId) {
        // Links to this app's notification settings.
        Intent intent = new Intent();
        intent.setAction("android.settings.APP_NOTIFICATION_SETTINGS");
        if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.O && channelId!=null){
            intent.setAction(Settings.ACTION_CHANNEL_NOTIFICATION_SETTINGS);
            intent.putExtra(Settings.EXTRA_CHANNEL_ID,channelId);
            intent.putExtra("android.provider.extra.APP_PACKAGE", getPackageName());
        }
        intent.putExtra("app_package", getPackageName());
        intent.putExtra("app_uid", getApplicationInfo().uid);
        startActivity(intent);
    }

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