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Building Simple Chat Client with Parse

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nesquena edited this page Sep 22, 2014 · 83 revisions

The following tutorial explains how to build a very simple chat application in Android using Parse backend-as-a-service.

1. Parse Registration

Follow the registration guide to sign up for a parse account unless you are already registered.

2. Setup Parse

Let's setup Parse into a brand new Android app following the steps below.

  • Generate a new android project in your IDE (minSDK 14) and call it SimpleChat.
    • Name the first activity ChatActivity.
  • Next, create an app in Parse and call it SimpleChat. Make note of the Application ID and Client Key values after you have done so.
  • Follow the the steps mentioned under the setup guide to create and setup your project in eclipse.
    • Drag the Parse jars into your libs folder
    • Create a class called ChatApplication which extends from android.app.Application
    • In the application, initialize parse with your application id and client key
  • Your application class should look like this after you have performed the above steps:
public class ChatApplication extends Application {
	public static final String YOUR_APPLICATION_ID = "AERqqIXGvzH7Nmg45xa5T8zWRRjqT8UmbFQeeI";
	public static final String YOUR_CLIENT_KEY = "8bXPznF5eSLWq0sY9gTUrEF5BJlia7ltmLQFRh";
	@Override
	public void onCreate() {
		super.onCreate();
		Parse.initialize(this, YOUR_APPLICATION_ID, YOUR_CLIENT_KEY);
	}
}
  • Make sure you have added these lines before the <application> tag in your AndroidManifest.xml.
<uses-permission android:name="android.permission.INTERNET" />
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
  • Also add the fully qualified name of your Application subclass to the <application> tag in your AndroidManifest.xml.
<application
  android:name="com.codepath.simplechat.ChatApplication"
  ...
  <activity ... />
/>

3. Design Messages Layout

Let's create an XML layout which allows us to post messages by typing into a text field. Open your layout file activity_chat.xml, add an EditText and a Button to compose and send text messages.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="${relativePackage}.${activityClass}" >

    <EditText
        android:id="@+id/etMessage"
        android:layout_toLeftOf="@+id/btSend"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignBottom="@+id/btSend"
        android:gravity="top"
        android:hint="@string/message_hint"
        android:imeOptions="actionSend"/>
      <Button
        android:id="@+id/btSend"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_vertical|right"
        android:paddingRight="10dp"
        android:layout_alignParentRight="true"
        android:text="@string/send"
        android:textSize="18sp" >
    </Button>

</RelativeLayout>
  • Add the following values to res-->values-->strings.xml file.
<string name="message_hint">Say anything</string>
<string name="send">Send</string>

4. Login With Anonymous ParseUser

For the sake of simplicity, we will use an anonymous user to log into our simple chat app. An anonymous user is a user that can be created without a username and password but still has all of the same capabilities as any other ParseUser. After logging out, an anonymous user is abandoned, and its data is no longer accessible.

Open your main activity class (ChatActivity.java) and make the following changes:

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.");
                } else {
                    startWithCurrentUser();
                }
            }
       });		
    }
}

5. Save Messages

Next, we will setup UI views in ChatActivity.java. On click of 'Send' button, we'll save the message object to Parse. This is done by constructing a new ParseObject and then calling saveInBackground() to persist data to the database.

...

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 sent message to parse.",
                             Toast.LENGTH_SHORT).show();
                    }
                });
                etMessage.setText("");
            }
        });
}

6. Verify Save

At this point, run your application and try to send a text to parse. If the save was successful, you should see 'Successfully sent message to parse.' toast on your screen. To make sure the data was saved, you can look at the message class in the Data Browser of your app on Parse.

7. Update Layout

  • Now that we have verified that messages are successfully being saved to your parse database, lets go ahead and build the UI to retrieve these messages. Open your layout file activity_chat.xmland add a ListView to display the text messages from parse.
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
  android:orientation="vertical"
  android:background="#ffffff"
  android:layout_width="match_parent"
  android:layout_height="match_parent">
    <ListView
      android:id="@+id/lvChat"
      android:transcriptMode="alwaysScroll"
      android:layout_alignParentTop="true"
      android:layout_alignParentLeft="true"
      android:layout_alignParentRight="true"
      android:layout_above="@+id/llSend"
      android:layout_width="wrap_content" 
      android:layout_height="match_parent" />
    <RelativeLayout 
      android:id="@+id/llSend"
      android:layout_alignParentBottom="true"
      android:layout_width="match_parent"
      android:background="#ffffff"
      android:paddingTop="5dp"
      android:paddingBottom="10dp"
      android:paddingLeft="0dp"
      android:paddingRight="0dp"
      android:layout_height="wrap_content" >
      <EditText
        android:id="@+id/etMessage"
        android:layout_toLeftOf="@+id/btSend"
        android:layout_alignBottom="@+id/btSend"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="top"
        android:hint="@string/message_hint"
        android:inputType="textShortMessage"
        android:imeOptions="actionSend"/>
      <Button
        android:id="@+id/btSend"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:gravity="center_vertical|right"
        android:paddingRight="10dp"
        android:layout_alignParentRight="true"
        android:text="@string/send"
        android:textSize="18sp" >
    </Button>
    </RelativeLayout>
</RelativeLayout>
  • We will be showing the logged in user's gravatar and messages on the right and the other gravatars and messages on the left. You can read more about creating gravatars here. We need to create another layout file to represent each chat message row in the list view. Put this into res/layout/chat_item.xml.
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >
    <ImageView
        android:id="@+id/ivProfileLeft"
        android:contentDescription="@string/profile_other"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@drawable/ic_launcher" />
    <TextView
        android:textSize="18sp"
        android:id="@+id/tvBody"
        android:padding="20dp"
        android:lines="3"
        android:layout_marginRight="64dp"
        android:layout_width="match_parent"
        android:layout_height="64dp">
    </TextView>
    <ImageView
        android:id="@+id/ivProfileRight"
        android:contentDescription="@string/profile_me"
        android:layout_marginLeft="-64dp"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@drawable/ic_launcher" />
</LinearLayout>
  • Add the following values to res-->values-->strings.xml file.
<string name="profile_me">My Profile Pic</string>
<string name="profile_other">Other profile pic</string>

8. Create Model Class

Now create Message.java class which will extend from ParseObject. This model class will be used to provide message data to ListView and can be used to retrieve and save messages to Parse.

@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);
    }
}

We also need to make sure to register this class with Parse before we call Parse.initialize within the ChatApplication.java file:

public class ChatApplication extends Application { @Override public void onCreate() { super.onCreate(); // Register your parse models ParseObject.registerSubclass(Message.class); // Add your initialization code here Parse.initialize(this, "7zBztvyG4hYQ9XghgfqYxfRcL3SMBYWAj0GUL", "iZWhgJRu6yKm3iNMbTaguLcNCV3qedijWL"); } }

With our model defined with Parse and properly registered, we can now use this model to store and retrieve message data.

9. Create Custom List Adapter

Create a class named ChatListAdapter.java with below code. This is a custom list adapter class which provides data to list view. In other words it renders the layout_row.xml in list by pre-filling appropriate information. Also, download Picasso image library and drag it to the libs folder of your project.

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;
	}

}

10. Bind Adapter to the ListView

Next, we will setup the ListView and bind our custom adapter to this ListView within the ChatActivity.java source file:

...
...

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("");
			}
	});
}

11. Receive Messages

Now we can fetch last 50 messages from parse and bind them to the ListView with the use of our custom messages adapter within ChatActivity.java:

...

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);
		query.setLimit(MAX_CHAT_MESSAGES_TO_SHOW);
		query.orderByDescending("createdAt");
                // Execute query for messages asynchronously
		query.findInBackground(new FindCallback<Message>() {
			public void done(List<Message> messages, ParseException e) {
				if (e == null) {					
					mMessages.clear();
					mMessages.addAll(messages);
					mAdapter.notifyDataSetChanged();
					lvChat.invalidate();
				} else {
					Log.d("message", "Error: " + e.getMessage());
				}
			}
		});
}

Now, we should be able to see the messages in the list after posting but we won't yet see them update on load or as new messages are created on other clients.

12. Refreshing Messages

Finally, let's periodically refresh the ListView with latest messages using a handler. The handler will call a runnable to fetch new messages every 100ms. This is a primitive "polling" rather than "push" technique for loading new messages but will work for the purposes of this simple project.

...

// 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();		
}

13. SimpleChatManifest.xml

The final manifest for this chat application looks like:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.codepath.simplechat"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk
        android:minSdkVersion="14"
        android:targetSdkVersion="19" />
    
    <uses-permission android:name="android.permission.INTERNET" />
	<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:name="com.codepath.simplechat.ChatApplication"
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
        <activity
            android:name=".ChatActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

14. Final Output

Run your project and test it out with your pair partner. Below is the final output.

Chat App|250

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