How to make a custom notification full-width?

Question

picture of my notification

I'm trying to create a full-width custom notification for my Flutter app on Android.
The problem is that the notification always appears centered with large horizontal margins, even though my layout uses match_parent for the width.

I'm calling native Kotlin through a MethodChannel, and everything displays, but the notification never spans the full width.

Custom Layout (custom_notification.xml)

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
 android:id="@+id/notification_background_layout"
 android:layout_width="match_parent"
 android:layout_height="wrap_content"
 android:orientation="horizontal"
 android:background="@color/notification_color">
 <!-- other views (ImageView, TextViews, etc.) -->
</LinearLayout>

Kotlin Notification Helper (NotificationHelper.kt)

package com.example.pomodo
import android.app.NotificationManager
import android.content.Context
import android.widget.RemoteViews
import androidx.core.app.NotificationCompat
import com.example.pomodo.R
class NotificationHelper(private val context: Context) {
 private val CHANNEL_ID = "custom_notification_channel"
 fun showCustomNotification(title: String, body: String, backgroundColor: Int) {
 val customNotificationLayout = RemoteViews(context.packageName, R.layout.custom_notification).apply {
 setTextViewText(R.id.notification_title, title)
 setTextViewText(R.id.notification_body, body)
 }
 val builder = NotificationCompat.Builder(context, CHANNEL_ID)
 .setSmallIcon(R.mipmap.ic_launcher)
 .setStyle(NotificationCompat.DecoratedCustomViewStyle()) // suspected issue
 .setCustomContentView(customNotificationLayout)
 .setPriority(NotificationCompat.PRIORITY_DEFAULT)
 val notificationManager =
 context.getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
 notificationManager.notify(1001, builder.build())
 }
}

• Mohammad Ali Ghasemian: please add pictures of your ui problem you are refering to.
• Supra Bob: @MohammadAliGhasemian hello thanks for the reply. ithink the picture is at the top of this post as "example"
• NirajDota: I don't think that's controllable. None of the applications have that.