如何设置自定义声音，每次出现通知时都会播放？

Question

我有一个下拉列表（spinner），其中显示了我外部存储中所有的MP3音乐文件。我希望每次弹出通知时都能播放MP3音乐，这将由用户选择。

用于读取外部存储中所有MP3文件的代码：

String selection = MediaStore.Audio.Media.IS_MUSIC + " != 0";
String[] projection = {
        MediaStore.Audio.Media.TITLE,
};
EnableRuntimePermission();
Cursor cursor = this.managedQuery(
        MediaStore.Audio.Media.EXTERNAL_CONTENT_URI,
        projection,
        selection,
        null,
        null);

spin.setOnItemSelectedListener(this);
List<String> songs = new ArrayList<String>();
while (cursor.moveToNext()) {
    songs.add(cursor.getString(0));
}

public void EnableRuntimePermission() {

    if (ActivityCompat.shouldShowRequestPermissionRationale(
            Pop_up_2.this,
            Manifest.permission.READ_EXTERNAL_STORAGE)) {

       // Toast.makeText(Pop_up_2.this, "Now you can read music files", Toast.LENGTH_LONG).show();

    } else {

        ActivityCompat.requestPermissions(Pop_up_2.this, new String[]{
                Manifest.permission.READ_EXTERNAL_STORAGE}, RequestPermissionCode);

    }
}

用于创建通知的代码：

NotificationCompat.Builder builder = new NotificationCompat.Builder(context, CHANNEL_ID)
            .setSmallIcon(R.drawable.ic_today_black_24dp)
            .setContentTitle(s3)
            .setContentText(message)
            .setPriority(NotificationCompat.PRIORITY_DEFAULT);

NotificationManagerCompat notification=NotificationManagerCompat.from(context);
notification.notify(NOTIFICATION_ID,builder.build());

编辑：我想知道是否有任何方法可以将String item1 = parent.getItemAtPosition(position).toString();解析为Uri，然后将该Uri参数设置为RingtoneManager

   Uri par=Uri.parse(item1);
    Uri alarmSound = RingtoneManager.setActualDefaultRingtoneUri(context,RingtoneManager.TYPE_NOTIFICATION,par);
                        .
                        .
                        .
                        .
                        .
builder.setSound(alarmSound);

但由于类型不兼容，我会收到错误消息。