How to retreive all data from firebase

Question

I am new to Android Studio and Firebase.

I am trying to retrive data from Firebase. I have node Orders and that node has unique id , choices and price .

This is how my Firebase looks like:

my-application0-8b65a
    Orders
        - Lw4hgcNwuCitXUKHdNh
          choices:"Pasta\n"
          price:19
        - Lw7zID257gZsJN9s0J3
          choices:"Shawarma\nPasta\n"
          price: 27

I have tried to use addValueEventListener to retrieve all orders from University, but when I run the app and go to the retreiving page, it goes back to main activity page. I am using listview(id:list_view) to display the data.

public class DataRetrived extends AppCompatActivity {    

    private DatabaseReference mDatabase;
    private ListView mUserList;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.dataactivity);
        mDatabase = FirebaseDatabase.getInstance().getReference();
        mUserList = findViewById(R.id.list_view);

        final List<Orders> ordersList = new ArrayList<>();
        mDatabase.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(DataSnapshot snapshot) {
                ordersList.clear();

                for (DataSnapshot postSnapshot : snapshot.getChildren()) {
                    Orders orders = postSnapshot.getValue(Orders.class);
                    ordersList.add(orders);
                }
            }

            @Override
            public void onCancelled(DatabaseError databaseError) {
                System.out.println("The read failed: ");
            }
        });
    }
}

Answer 1

Firebase ref = new Firebase(FIREBASE_URL);

ref.addValueEventListener(new ValueEventListener() {

@Override

public void onDataChange(DataSnapshot snapshot) {

Log.e("Count " ,""+snapshot.getChildrenCount());

for (DataSnapshot postSnapshot: snapshot.getChildren()) {

<YourClass> post = postSnapshot.getValue(<YourClass>.class);

Log.e("Get Data", post.<YourMethod>());

}

}

@Override

public void onCancelled(FirebaseError firebaseError) {

Log.e("The read failed: " ,firebaseError.getMessage());

}

});

Answer 2

First add a reference to node Orders and then inside onDataChange remove the for loop to be able to retrieve the object Orders .

Change this:

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

into this:

mDatabase = FirebaseDatabase.getInstance().getReference("Orders");

Then change the onDataChange() to the following:

  public void onDataChange(DataSnapshot snapshot) {
          ordersList.clear();
                Orders orders = snapshot.getValue(Orders.class);
                ordersList.add(orders);
        }