Why data from firebase database did not show in Spinner?

Question

As refer in this link. I want to try in my coding apps. But it didnt retrieve any data from my firebase database. I just cant figure out how to fix it. Can someone please help me. Is there any idea, where did I miss?

My firebase database as show image below:-

Spinner coding:-

mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.keepSynced(true);

mDatabase.child("Advertisement").child(mAuth.getUid()).addValueEventListener(new ValueEventListener()
        {
            @Override
            public void onDataChange(DataSnapshot dataSnapshot)
            {
                //final List<String> name = new ArrayList<String>();
                ArrayList<String> identity = new ArrayList<>();
                identity.add(0, "Choose Tuition Centre");

                for (DataSnapshot nameSnapshot: dataSnapshot.getChildren())
                {
                    String tuitionName = nameSnapshot.child("adstuitioname").getValue(String.class);
                    identity.add(tuitionName);
                }

                ArrayAdapter<String> nameAdapter = new ArrayAdapter<String>(RatingActivity.this, android.R.layout.simple_spinner_item, identity);
                nameAdapter.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
                mName.setAdapter(nameAdapter);
            }


            @Override
            public void onCancelled(DatabaseError databaseError) {

            }
        });

        mName.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()
        {
            @Override
            public void onItemSelected(AdapterView<?> parent, View view, int position, long id)
            {
                if(position==0)
                {
                    //Toast.makeText(getApplicationContext(),"No Item Selected",Toast.LENGTH_LONG).show();
                }

                else
                {
                    Toast.makeText(getApplicationContext(),parent.getItemAtPosition(position) +" Selected",Toast.LENGTH_SHORT).show();
                }
            }

            @Override
            public void onNothingSelected(AdapterView<?> parent)
            {
                // TODO Auto-generated method stub
            }
        });

Answer 1

Add listener as below :

DatabaseReference mDatabaseRef =  
                            FirebaseDatabase.getInstance().getReference();
ArrayList<String> list=new ArrayList<>();
mDatabaseRef.child("Advertisement")
            .addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(DataSnapshot dataSnapshot) {
                   for (DataSnapshot snapshot :dataSnapshot.getChildren()) 
                     {
                        Advertisementject advertisement= 
                                snapshot.getValue(Advertisement.class);
                        //replace Object.class with your class name
                        //get your key value here from your "Custom class" 
                        // which contains "adstutioname" 
                        // add in list
                        list.add(advertisement.getAdstutuioname());
                    }

                    //set adapter
                }

                @Override
                public void onCancelled(DatabaseError databaseError) {

                }
            });

generate class like this

public class Advertisement{

@SerializedName("adstutuioname")
@Expose
private String adstutuioname;

public String getAdstutuioname() {
  return adstutuioname;
}

public void setAdstutuioname(String adstutuioname) {
  this.adstutuioname = adstutuioname;
}

}

• Your class contains all your params and .
• Replace Object with this class

Answer 2

I hope the problem is with your getValue() method. Firebase getValue method returns an Object, and you are expecting a String. Please modify this line to convert your Object to String -

String tuitionName = nameSnapshot.child("adstuitioname").getValue(String.class).toString();

Answer 3

It's not clear if you're trying to read once, or watch changes Difference between addValueEventListener() and addListenerForSingleValueEvent() of firebase

First things first, look if you are getting a database error

@Override
public void onCancelled(DatabaseError databaseError) {
    // Toast or print the databaseError, don't ignore it
}

Then look where you're adding a listener - mDatabase.child("Advertisement").child(mAuth.getUid())., which from your picture is every element at the level of -LNZ6....

For that level, you have a list of object's, so you can need to use a loop, and as shown from some examples on Firebase site, it's recommended that you make an object, but you still can use child method for a certain field as you're trying to do

But if a field doesn't exist, you get null value, and Adapters cannot hold nulls, so you must ignore or set some default value.

ArrayList<String> identity = new ArrayList<>();
identity.add(0, "Choose Tuition Centre");

for (DataSnapshot nameSnapshot: dataSnapshot.getChildren())  {
    String tuitionName = nameSnapshot.child("adstuitioname").getValue(String.class);
    Log.d("DEBUG TUITION", String.valueOf(tuitionName);  // look for this in your logs 
    identity.add(tuitionName == null ? "none" : tuitionName);
}
ArrayAdapter<String> nameAdapter =...