Building Simple Chat Client with Parse - kmolo/android_guides GitHub Wiki

public class ChatActivity extends Activity {
    private static final String TAG = ChatActivity.class.getName();
    private static String sUserId;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_chat);
        // User login
        if (ParseUser.getCurrentUser() != null) { // start with existing user
            startWithCurrentUser();
        } else { // If not logged in, login as a new anonymous user
            login();
        }
    }
    
    // Get the userId from the cached currentUser object
    private void startWithCurrentUser() {
        sUserId = ParseUser.getCurrentUser().getObjectId();		
    }
    
    // Create an anonymous user using ParseAnonymousUtils and set sUserId 
    private void login() {
        ParseAnonymousUtils.logIn(new LogInCallback() {
	    @Override
	    public void done(ParseUser user, ParseException e) {
                if (e != null) {
                    Log.d(TAG, "Anonymous login failed: " + e.toString());
                } else {
                    startWithCurrentUser();
                }
            }
       });		
    }
}

...

public static final String USER_ID_KEY = "userId";

private EditText etMessage;
private Button btSend;

...

// Get the userId from the cached currentUser object
private void startWithCurrentUser() {
    sUserId = ParseUser.getCurrentUser().getObjectId();  
    setupMessagePosting();
}

// Setup button event handler which posts the entered message to Parse
private void setupMessagePosting() {
        // Find the text field and button
        etMessage = (EditText) findViewById(R.id.etMessage);
        btSend = (Button) findViewById(R.id.btSend);
        // When send button is clicked, create message object on Parse
        btSend.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                String data = etMessage.getText().toString();
                ParseObject message = new ParseObject("Message");
                message.put(USER_ID_KEY, sUserId);
                message.put("body", data);
                message.saveInBackground(new SaveCallback() {
                    @Override
                    public void done(ParseException e) {
                    	Toast.makeText(ChatActivity.this, "Successfully created message on Parse",
                             Toast.LENGTH_SHORT).show();
                    }
                });
                etMessage.setText("");
            }
        });
}

@ParseClassName("Message")
public class Message extends ParseObject {
    public String getUserId() {
    	return getString("userId");
    }
    
    public String getBody() {
    	return getString("body");
    }
    
    public void setUserId(String userId) {
        put("userId", userId);	
    }
    
    public void setBody(String body) {
    	put("body", body);
    }
}

public class ChatApplication extends Application {
	// ...
	public void onCreate() {
		super.onCreate();
		// Register your parse models here
		ParseObject.registerSubclass(Message.class);
		// Existing initialization happens after all classes are registered
		Parse.initialize(this, YOUR_APPLICATION_ID, YOUR_CLIENT_KEY);
	}
}

public class ChatListAdapter extends ArrayAdapter<Message> {	
	private String mUserId;
	
	public ChatListAdapter(Context context, String userId, List<Message> messages) {
	        super(context, 0, messages);
	        this.mUserId = userId;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		if (convertView == null) {
			convertView = LayoutInflater.from(getContext()).
			    inflate(R.layout.chat_item, parent, false);
			final ViewHolder holder = new ViewHolder();
			holder.imageLeft = (ImageView)convertView.findViewById(R.id.ivProfileLeft);
			holder.imageRight = (ImageView)convertView.findViewById(R.id.ivProfileRight);
			holder.body = (TextView)convertView.findViewById(R.id.tvBody);
			convertView.setTag(holder);
		}
		final Message message = (Message)getItem(position);
		final ViewHolder holder = (ViewHolder)convertView.getTag();
		final boolean isMe = message.getUserId().equals(mUserId);
		// Show-hide image based on the logged-in user. 
                // Display the profile image to the right for our user, left for other users.
		if (isMe) {
			holder.imageRight.setVisibility(View.VISIBLE);
			holder.imageLeft.setVisibility(View.GONE);
			holder.body.setGravity(Gravity.CENTER_VERTICAL | Gravity.RIGHT);
		} else {
			holder.imageLeft.setVisibility(View.VISIBLE);
			holder.imageRight.setVisibility(View.GONE);
			holder.body.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
		}
		final ImageView profileView = isMe ? holder.imageRight : holder.imageLeft;
		Picasso.with(getContext()).load(getProfileUrl(message.getUserId())).into(profileView);
		holder.body.setText(message.getBody());
		return convertView;
	}
	
	// Create a gravatar image based on the hash value obtained from userId
	private static String getProfileUrl(final String userId) {
		String hex = "";
		try {
			final MessageDigest digest = MessageDigest.getInstance("MD5");
			final byte[] hash = digest.digest(userId.getBytes());
			final BigInteger bigInt = new BigInteger(hash);
			hex = bigInt.abs().toString(16);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return "http://www.gravatar.com/avatar/" + hex + "?d=identicon";
	}
	
	final class ViewHolder {
		public ImageView imageLeft;
		public ImageView imageRight;
		public TextView body;
	}

}

...
...

private ListView lvChat;
private ArrayList<Message> mMessages;
private ChatListAdapter mAdapter;

...
	
// Setup message field and posting
private void setupMessagePosting() {
    	etMessage = (EditText) findViewById(R.id.etMessage);
    	btSend = (Button) findViewById(R.id.btSend);
    	lvChat = (ListView) findViewById(R.id.lvChat);
    	mMessages = new ArrayList<Message>();
    	mAdapter = new ChatListAdapter(ChatActivity.this, sUserId, mMessages);
    	lvChat.setAdapter(mAdapter);
    	btSend.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				String body = etMessage.getText().toString();
				// Use Message model to create new messages now      
				Message message = new Message();
				message.setUserId(sUserId);
				message.setBody(body);
				message.saveInBackground(new SaveCallback() {
					@Override
					public void done(ParseException e) {
						receiveMessage();
					}
				});
				etMessage.setText("");
			}
	});
}

...

private static final int MAX_CHAT_MESSAGES_TO_SHOW = 50;

...

// Query messages from Parse so we can load them into the chat adapter
private void receiveMessage() {
                // Construct query to execute
		ParseQuery<Message> query = ParseQuery.getQuery(Message.class);
                // Configure limit and sort order
		query.setLimit(MAX_CHAT_MESSAGES_TO_SHOW);
		query.orderByAscending("createdAt");
		// Execute query to fetch all messages from Parse asynchronously
                // This is equivalent to a SELECT query with SQL
		query.findInBackground(new FindCallback<Message>() {
			public void done(List<Message> messages, ParseException e) {
				if (e == null) {					
					mMessages.clear();
					mMessages.addAll(messages);
					mAdapter.notifyDataSetChanged(); // update adapter
					lvChat.invalidate(); // redraw listview
				} else {
					Log.d("message", "Error: " + e.getMessage());
				}
			}
		});
}

...

// Create a handler which can run code periodically
private Handler handler = new Handler();

...

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_chat);
    if (ParseUser.getCurrentUser() != null) {
        startWithCurrentUser();
    } else {
    	login();
    }
    // Run the runnable object defined every 100ms
    handler.postDelayed(runnable, 100);
}

// Defines a runnable which is run every 100ms
private Runnable runnable = new Runnable() {
    @Override
    public void run() {
       refreshMessages();
       handler.postDelayed(this, 100);
    }
};

private void refreshMessages() {
    receiveMessage();		
}