android找不到R类

import org.cocos2d.demo.R;

org.cocos2d.demo 包名（creator hello world自带）

    NotificationManagerCompat notificationManager = NotificationManagerCompat.from(this);
    NotificationCompat.Builder builder = new NotificationCompat.Builder(this, CHANNEL_ID);
    builder.setContentTitle("Picture Download")
            .setContentText("Download in progress")
            .setSmallIcon(R.drawable.ic_notification)
            .setPriority(NotificationCompat.PRIORITY_LOW);

R.drawable.ic_notification res文件夹下面drawable文件夹 下面ic_notification.png图片