Retrieve Data From Firebase Database On Button Click

I'm writing an app that allows users to collaborate on inventory by uploading data to a database hosted by firebase. I can write data to it no problem, however it only wants to let

Solution 1:

You need to use addListenerForSingleValueEvent() to retrieve data

DatabaseReference mDatabase;
mDatabase = FirebaseDatabase.getInstance().getReference();
mDatabase.child("<childName>").addListenerForSingleValueEvent(newValueEventListener(){
        @OverridepublicvoidonDataChange(DataSnapshot dataSnapshot) {

        }

        @OverridepublicvoidonCancelled(DatabaseError databaseError) {

        }
});

Here in child you need to mention your child node name

If you want to get change of whole database, simply remove child so it look like mDatabase.addListenerForSingleValueEvent()

Solution 2:

You can use addValueEventListener() to retrieve data when an event is triggered.

In your onClick() method you can write :

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

// In the database whenever any data is changed then the below code snipped is going to be executed.
mDatabase.child("<dbLocationTag>").addValueEventListener(newValueEventListener() {
            @OverridepublicvoidonDataChange(DataSnapshot dataSnapshot) {

                // the changed value is going to be stored into the dataSnapshot// to retrieve value from dataSnapshot we writeString value = dataSnapshot.getValue(String.class);
                mValueView.setText(value);

                // NOTE: if you've multiple childs of same node then you can use Map to display all of them : EG: /*Map<String, String> map = dataSnapshot.getValue(Map.class);
                String val1 = map.get("val1");
                String val2 = map.get("val2");
                String val3 = map.get("val3");
                Log.v("TAG", "Value 1 "+val1);
                Log.v("TAG", "Value 2 "+val2);
                Log.v("TAG", "Value 3 "+val3);
*/
            }

            @OverridepublicvoidonCancelled(FirebaseError firebaseError) {

                mValueView.setText(firebaseError.toString());

            }
        });

Solution 3:

addButton.setOnClickListener(newView.OnClickListener() {
    @OverridepublicvoidonClick(View v) {
        DatabaseReference mRef = mDatabaseReference.getDatabase().getReference("users");
        ValueEventListener valueEventListener = newValueEventListener() {
            @OverridepublicvoidonDataChange(DataSnapshot dataSnapshot) {
                for (DataSnapshot ds : dataSnapshot.getChildren()) {
                    Log.d(TAG, "" + ds.getKey());
                }
            }

            @OverridepublicvoidonCancelled(DatabaseError databaseError) {

            }
        };
    }
});
mRef.addListenerForSingleValueEvent(valueEventListener);

The above method worked for me. Hope it helps for you, too.