从Firebase检索数据到Listview

Question

I am trying to retrieve data from Firebase but nothing pulls through. The app is written successfully however when it tries to get the info back it just shows a blank screen. My Firebase structure is Saica>Calendar>key>Data

I have included a picture of my Firebase Structure

This is my code:

public class Admin_ViewEvent extends AppCompatActivity {

private ListView mListView;
private ArrayList<String> mMeetings = new ArrayList<>();
private Firebase mRef;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_admin__view_event);

    mRef = new Firebase("https://saica-sgb-77a4f.firebaseio.com/Meetings");
    mListView = (ListView) findViewById(R.id.ListView);

    final ArrayAdapter<String> arrayAdapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, mMeetings);
    mListView.setAdapter(arrayAdapter);

    mRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            String value = dataSnapshot.getValue(String.class);
            mMeetings.add(value);
            arrayAdapter.notifyDataSetChanged();
        }

        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {

        }

Answer 1

As per your old Screenshot Reference you can get date and description from parent Calendar node. You can use below snippet to get details from Meetings node.

FirebaseDatabase.getInstance().getReference().child("Calendar").addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            for(DataSnapshot childSnapShot : dataSnapshot.getChildren()) {

                String date = (String) childSnapShot.child("date").getValue();
                String desc = (String) childSnapShot.child("description").getValue();

            }
        }

        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });

Answer 2

Based on the line

mRef = new Firebase("https://saica-sgb-77a4f.firebaseio.com/Meetings");

it looks like you are using the wrong firebase sdk. It's either an old version or the java server sdk, but definitely not a recent android sdk.

Check you build.gradle : you should have a line like this :

compile "com.google.firebase:firebase-database:10.0.0"

To connect to your database and get a reference :

• Download the file google-services.json from the firebase console to your app/ folder.

• Create the database reference like this :

   FirebaseDatabase db = FirebaseDatabase.getInstance(); DatabaseReference mRef = db.getReference("Meetings") ;