Data Binding in 2015: Reactive Programming and Firebase Code Snippets

MainActivity.java

public class MainActivity extends Activity {

    private ListView mListView;
    private ArrayList<Message> mMessages;
    private ArrayAdapter mAdapter;

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

        // Step -1: Initialize fields
        mListView = (ListView)findViewById(R.id.listView);
        mMessages = new ArrayList<Message>();

        Firebase.setAndroidContext(this); // Step 0: Set the Android context for Firebase
        Firebase ref = new Firebase("https://droidcon2015.firebaseio.com");  // Step 1: Connect to a Firebase ref

        ref.addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {
                mMessages.add(dataSnapshot.getValue(Message.class));  // Step 2: Convert DataSnapshot to Message, add Message
                mAdapter.notifyDataSetChanged();
            }

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

            }

            @Override
            public void onChildRemoved(DataSnapshot dataSnapshot) {

            }

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

            }

            @Override
            public void onCancelled(FirebaseError firebaseError) {

            }
        });

        // Step 3: Add new ArrayAdapter that inflates our views
        mAdapter = new ArrayAdapter<Message>(this, android.R.layout.simple_list_item_2, mMessages) {
            @Override
            public View getView(int position, View convertView, ViewGroup parent) {
                View row = convertView;

                if (row == null) {
                    LayoutInflater inflator = LayoutInflater.from(getContext());
                    row = inflator.inflate(android.R.layout.simple_list_item_2, null);
                }

                TextView textView = (TextView) row.findViewById(android.R.id.text1);
                TextView nameView = (TextView) row.findViewById(android.R.id.text2);

                Message message = mMessages.get(position);
                textView.setText(message.getText());
                nameView.setText(message.getName());

                return row;
            }
        };

        // Step 4: Connect ArrayAdapter to ListView
        mListView.setAdapter(mAdapter);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

MainActivityFirebaseUI.java

public class MainActivityFirebaseUI extends Activity {

    private ListView mListView;
    private FirebaseListAdapter<Message> mFirebaseAdapter;

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

        Firebase.setAndroidContext(this); // Step 0: Set the Android context for Firebase
        Firebase ref = new Firebase("https://droidcon2015.firebaseio.com");  // Step 1: Connect to a Firebase ref

        // Step 2: Hook up FirebaseListAdapter 
        mFirebaseAdapter = new FirebaseListAdapter<Message>(this, Message.class, android.R.layout.simple_list_item_2, ref) {
            @Override
            protected void populateView(View view, Message message) {
                // Step 3: Populate view with message
                TextView textView = (TextView) view.findViewById(android.R.id.text1);
                TextView nameView = (TextView) view.findViewById(android.R.id.text2);
                textView.setText(message.getText());
                nameView.setText(message.getName());
            }
        };

        // Step 4: Connect ArrayAdapter to ListView
        mListView.setAdapter(mFirebaseAdapter);
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        int id = item.getItemId();

        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

Message.java

public class Message {

    private String name;
    private String text;

    public Message() {
        /* Empty constructor */
    }

    public Message(String name, String text) {
        this.name = name;
        this.text = text;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getText() {
        return text;
    }

    public void setText(String text) {
        this.text = text;
    }
}