我如何获取具有相同String key android firebase的所有项目

Question

I want to get all the items which have same league id

I want to get all the items which have same league id within the teams node and in that node I have push key and then an object, with Firebase query , If any one knows about it please help. Link to Image -> https://i.stack.imgur.com/XzJo2.jpg
and result is > System.out: LOG DataSnapshot { key = teams, value = null }

val query = databaseRef.child("teams").orderByChild("leagueId").equalTo("LS9t7MgdIuHrDP0vEME")
            query.addListenerForSingleValueEvent(object : ValueEventListener {
                override fun onDataChange(dataSnapshot: DataSnapshot) {
                    println("LOG $dataSnapshot")

                }

                override fun onCancelled(databaseError: DatabaseError) {

                }
            })

Answer 1

To get all the items within the teams node that correspond to a specific id, please use the following lines of code:

DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
Query query = rootRef.child("teams").orderByChild("leagueId").equalsTo(desiredId);
ValueEventListener valueEventListener = new ValueEventListener() {
    @Override
    public void onDataChange(DataSnapshot dataSnapshot) {
        for(DataSnapshot ds : dataSnapshot.getChildren()) {
            String team = ds.child("team").getValue(String.class);
            Log.d(TAG, team);
        }
    }

    @Override
    public void onCancelled(@NonNull DatabaseError databaseError) {
        Log.d(TAG, databaseError.getMessage()); //Don't ignore errors!
    }
};
query.addListenerForSingleValueEvent(valueEventListener);

In which the desiredId should hold a value as -LS9t ... vEME . The output in your logcat will be, the name of all teams that have the id equal to -LS9t ... vEME .