为了避免Android MediaStyle通知图片出现马赛克，建议使用高清晰度的图片作为largeIcon，并调整其尺寸以适应通知尺寸。以下是示例代码：

Kotlin：

val bitmap = BitmapFactory.decodeResource(resources, R.drawable.notification_icon)
val size = resources.getDimensionPixelSize(android.R.dimen.notification_large_icon_height)
val resizedBitmap = Bitmap.createScaledBitmap(bitmap, size, size, false)

val builder = NotificationCompat.Builder(this, CHANNEL_ID)
        .setContentTitle("Title")
        .setContentText("Content text")
        .setSmallIcon(R.drawable.notification_icon)
        .setLargeIcon(resizedBitmap)
        .setStyle(NotificationCompat.MediaStyle())
        .setPriority(NotificationCompat.PRIORITY_DEFAULT)

Java：

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.notification_icon);
int size = getResources().getDimensionPixelSize(android.R.dimen.notification_large_icon_height);
Bitmap resizedBitmap = Bitmap.createScaledBitmap(bitmap, size, size, false);

NotificationCompat.Builder builder = new NotificationCompat.Builder(this, CHANNEL_ID)
        .setContentTitle("Title")
        .setContentText("Content text")
        .setSmallIcon(R.drawable.notification_icon)
        .setLargeIcon(resizedBitmap)
        .setStyle(new NotificationCompat.MediaStyle())
        .setPriority(NotificationCompat.PRIORITY_DEFAULT);

其中，上述代码中的"notification_icon"为要显示的图片资源文件名。通过调整resizedBitmap的大小，从而解决Android MediaStyle 通知图片出现马赛克的问题。