从特定位置从 firebase 获取数据

Question

Hy, I'm writing an application that has to get specific data from firebase using the position of the item in the listView. My problem is that I have no idea how to take it this item on firebase.

For all child of Torneo I have to control all the nameCreator. I have tried this:

public Boolean RegisterUser(Data data, final int position, final Context c){
        boolean registration;
        final ArrayList<String> Creator = new ArrayList<>();



        databaseReference.orderByChild("Tornei").equalTo(Integer.toString(position)).addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot) {
                for(DataSnapshot datas: dataSnapshot.getChildren()){
                   Creator.add(data.child("nameCreator").getValue().toString());
                }
            }
            @Override
            public void onCancelled(DatabaseError databaseError) {
            }
        });
        if(Creator.equals(data.getNameCreator())){
            registration = false;
        }else{
            registration = true;
        }

        return registration;
    }

Data is a class with some getter and setter that I have created. position is the position of the element on the list view.

Thanks for answers.

Answer 1

Change the following:

databaseReference.orderByChild("Tornei").equalTo(Integer.toString(position)).addListenerForSingleValueEvent(new ValueEventListener() {

into this:

databaseReference.child("Tornei").addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot datas: dataSnapshot.getChildren()){
               Creator.add(datas.child("nameCreator").getValue().toString());
    if(Creator.equals(data.getNameCreator())){
        registration = false;
    }else{
        registration = true;
    }
            }
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
        }
    });

Then you will be able to loop and retrieve the value of nameCreator

Answer 2

It's easy.

【Step 1 | Get Snapshot Data and Save in Global Variable】

DatabaseReference rootReference = FirebaseDatabase.getInstance().getReference();
DatabaseReference fruitsReference = rootReference.child("fruits");

DataSnapshot fruitsData;

@Override
protected void onStart() {
    super.onStart();

    fruitsReference.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshots) {
            fruitsData = dataSnapshots;        
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
        }
    });
}

---

【Step 2 | Find Your Target Position through the Loop】

public void onClick(View view) {
    int index = 0;

    for (DataSnapshot childSnapshot : fruitsData.getChildren()) {
        if (index == 1) {        //your target position
            DatabaseReference currentFruitReference = childSnapshot.getRef();

            currentFruitReference.setValue("peach");        //do whatever you want
        }

        index++;
    }
}