Notification expanded

I have the following codes (XML and notification respectively) for a notification plus it is small, I would like it to be expanded to suit everything

XML

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/onGoingNotification"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_gravity="center_horizontal"
android:background="@color/white"
android:orientation="horizontal">

<ImageView
    android:id="@+id/imageView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_gravity="left|center_vertical"
    android:src="@mipmap/without_photo"
    android:layout_centerVertical="true"
    android:layout_alignParentLeft="true"
    android:padding="6dp"/>

<TextView
    android:id="@+id/sub_title"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_alignEnd="@+id/next"
    android:layout_alignLeft="@+id/previous"
    android:layout_alignRight="@+id/next"
    android:layout_alignStart="@+id/previous"
    android:layout_centerVertical="true"
    android:text="sub text"
    android:layout_marginLeft="8dp"
    android:textColor="@color/black_transparent" />


<ImageButton
    android:id="@+id/next"
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:background="@color/transparent"
    android:src="@mipmap/ic_next_black"
    android:layout_alignTop="@+id/Play_pause"
    android:layout_alignParentRight="true"
    android:layout_alignParentEnd="true"
    android:layout_marginRight="18dp"/>

<ImageButton
    android:id="@+id/Play_pause"
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:layout_alignParentBottom="true"
    android:layout_gravity="bottom"
    android:layout_marginRight="36dp"
    android:layout_toLeftOf="@+id/next"
    android:background="@color/transparent"
    android:longClickable="true"
    android:src="@mipmap/play"
    android:layout_marginBottom="8dp" />

<ImageButton
    android:id="@+id/previous"
    android:layout_width="48dp"
    android:layout_height="48dp"
    android:layout_alignTop="@+id/Play_pause"
    android:layout_marginRight="36dp"
    android:layout_toLeftOf="@+id/Play_pause"
    android:background="@color/transparent"
    android:src="@mipmap/ic_prev_black" />

<TextView
    android:id="@+id/title_notification"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_above="@+id/sub_title"
    android:layout_alignEnd="@+id/sub_title"
    android:layout_alignLeft="@+id/sub_title"
    android:layout_alignRight="@+id/sub_title"
    android:layout_alignStart="@+id/sub_title"
    android:layout_marginBottom="18dp"
    android:text="Large Text"
    android:textAppearance="?android:attr/textAppearanceLarge"
    android:textColor="@color/black" />
</RelativeLayout>

and Notification:

private Notification ongoingNotification() {
    Intent intent = new Intent(getApplicationContext(),
   PlayerService.class);
    intent.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK);
    int icon = R.mipmap.ic_notification;
    Notification notification = new Notification(icon, "", 0);

    String title = "meuplayer";
    String msg = "Tocando. Clique para abrir.";

    if (currentStreamBeingPlayed != null) {
        msg = currentStreamBeingPlayed.getTitle();
    }

    PendingIntent previousSongPendingIntent = createPendingIntent(PlayerUI.PREVIOUS_SONG);
    PendingIntent pausePendingIntent = createPendingIntent(PlayerService.PAUSE);
    PendingIntent nextSongPendingIntent = createPendingIntent(PlayerUI.NEXT_SONG);
    PendingIntent playPendingIntent = createPendingIntent(PlayerService.PLAY);
    PendingIntent PlayerNotificationPendingIntent = createPendingIntent(PlayerService.PLAYERNOTIFICATION);

    NotificationCompat.Builder mBuilder = new NotificationCompat.Builder(getApplicationContext());
    RemoteViews contentView = new RemoteViews(getPackageName(), R.layout.player_notification);
    mBuilder.setContent(contentView);
    contentView.setOnClickPendingIntent(R.id.onGoingNotification, PlayerNotificationPendingIntent);
    contentView.setTextViewText(R.id.title_notification, title);
    contentView.setTextViewText(R.id.sub_title, msg);
    if (isPlayingNow) {
        contentView.setImageViewResource(R.id.Play_pause, R.mipmap.pause);
        contentView.setOnClickPendingIntent(R.id.Play_pause, pausePendingIntent);
    } else {
        contentView.setImageViewResource(R.id.Play_pause, R.mipmap.play);
        contentView.setOnClickPendingIntent(R.id.Play_pause, playPendingIntent);
    }
    contentView.setOnClickPendingIntent(R.id.next, previousSongPendingIntent);
    contentView.setOnClickPendingIntent(R.id.previous, nextSongPendingIntent);


    if (currentStreamBeingPlayed != null && currentStreamBeingPlayed.getPicture() != null) {
        try {
            URL urlPicture = new URL(currentStreamBeingPlayed.getPicture());
            Bitmap largeIcon = ImageHandler.decodeURLstreamToBitmap(urlPicture, getResources().getDimensionPixelSize(android.R.dimen.notification_large_icon_width), getResources().getDimensionPixelSize(android.R.dimen.notification_large_icon_height));
            contentView.setImageViewBitmap(R.id.imageView, largeIcon);
        } catch (MalformedURLException e) {
        } catch (Resources.NotFoundException e) {
        } catch (IOException e) {
        }
    }
    notification.contentView = contentView;

    Intent notificationIntent = new Intent(this, PlayerUI.class);
    PendingIntent contentIntent = PendingIntent.getActivity(this, 0, notificationIntent, 0);
    notification.contentIntent = contentIntent;
    return notification;
}

private PendingIntent createPendingIntent(String type) {
    //Create an Intent for the BroadcastReceiver
    Intent intent = new Intent(this, PlayerOnGoingNotificationBroadcastReceiver.class);

    intent.setAction(type);

    //Create the PendingIntent
    PendingIntent pendingIntent = PendingIntent.getBroadcast(this, 0, intent, PendingIntent.FLAG_UPDATE_CURRENT);

    return pendingIntent;
}