如何从Firebase数据库检索随机值？

Question

我有一个带有这样的树的firebase数据库

tvthemetunes
airwolf value "url to air wolftheme"
eastenders value "url to eastenders"
knight rider value "url to nightrider"

等等…

在我的应用程序中，用户下载项目，而项目下载时，电视主题将从URL播放。当单个项目发生价值事件时，我可以使其正常运行。我希望它从列表中随机选择一个值。如何做到这一点？

由于我的应用程序不包含任何内容，因此编辑可以使用回收视图方法

这是我的单项代码

protected Dialog onCreateDialog(int id) {

    switch (id) {
        case progress_bar_type:
    //Here is where i play the theme
            getthemetune();
            pDialog = new ProgressDialog(c);
            pDialog.setTitle(MY Title);
            pDialog.setMessage(MY Message);
            pDialog.setIcon(R.mipmap.ic_launcher);
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(false);
            pDialog.show();

            return pDialog;
        default:

            return null;
    }
}
private void getthemetune(){
  mthemetuneref = FirebaseDatabase.getInstance();
    DatabaseReference ref = mthemetuneref.getReference().child(MYREF);
    ref.child("airwolf").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
//Edit to add Alex's answer?
          long childrenCount = datasnapshot.getChildrenCount();
          int count = (int) childrenCount;

//Dont know how to use this
          int randomNumber = new Random().nextInt(count);

            plysound();

        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}
private void plysound(){
    mp = new MediaPlayer();
    String j =
    tvThemeTune.toString();
    Log.i("Url",j);
    try {
        mp.setDataSource(j);
    } catch (IOException e) {
        e.printStackTrace();
    }
    try {
        mp.prepare();
    } catch (IOException e) {
        e.printStackTrace();
    }
    mp.start();
    Log.i("Sound playing", "Ok");
    mp.setLooping(true);
}

Answer 1

要解决此问题，请使用以下代码行：

long childrenCount = snapshot.getChildrenCount();
int count = (int) childrenCount;
int randomNumber = new Random().nextInt(count);

然后使用for循环使用随机数提取该值：

int i=0;
String themeTune; //Your random themeTune will be stored here
for (DataSnapshot snap : snapshot.getChildren()) {
    if(i = randomNumber) {
        themeTune = snap.getValue(String.class);
        break;
    }
    i++;
}
plysound();