Building Simple Chat Client with Parse

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

Note: This chat application is by no means fully-featured or production ready. It's merely an illustration on quickly building a fully connected application using Parse

1. Parse Registration

First, we need to sign up for a Parse account unless we 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 16) 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.

  • Open the Parse Quickstart Android Guide for updated instructions.

  • Add the following to your app/build.gradle:

    dependencies {
      compile 'com.parse.bolts:bolts-android:1.+'
      compile 'com.parse:parse-android:1.+'
    }

  • 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" />

• Add the following lines to your AndroidManifest.xml inside the application tag

<meta-data
    android:name="com.parse.APPLICATION_ID"
    android:value="{APPLICATION_ID}" />
<meta-data
    android:name="com.parse.CLIENT_KEY"
    android:value="{CLIENT_KEY}" />

Note: Make sure you replace {APPLICATION_ID} and {CLIENT_KEY} with your application ID and client key respectively from Parse.

• Create a class called ChatApplication which extends from android.app.Application

  • In the application, initialize parse

    public class ChatApplication extends Application {
        @Override
        public void onCreate() {
            super.onCreate();
            // [Optional] Power your app with Local Datastore. For more info, go to
            // https://parse.com/docs/android/guide#local-datastore
            Parse.enableLocalDatastore(this);
            Parse.initialize(this);
        }
    }

• Add the qualified android:name of your Application subclass to the <application> tag in your AndroidManifest.xml.

  <application
    android:name=".ChatApplication"
    android:icon="@mipmap/ic_launcher"
    android:label="@string/app_name"
    ...>
        <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.

<?xml version="1.0" encoding="utf-8"?>
<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>

The imeOptions attribute is used to control the icon in the Soft Keyboard. The gravity attribute will center the button vertically AND right horizontally.

• 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 {
    static final String TAG = ChatActivity.class.getSimpleName();

    @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
    void startWithCurrentUser() {
        // TODO:
    }
    
    // Create an anonymous user using ParseAnonymousUtils and set sUserId 
    void login() {
        ParseAnonymousUtils.logIn(new LogInCallback() {
	    @Override
	    public void done(ParseUser user, ParseException e) {
                if (e != null) {
                    Log.e(TAG, "Anonymous login failed: ", e);
                } 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 class ChatActivity extends AppCompatActivity {
...
    static final String USER_ID_KEY = "userId";
    static final String BODY_KEY = "body";

    EditText etMessage;
    Button btSend;

...

    // Get the userId from the cached currentUser object
    void startWithCurrentUser() {
        setupMessagePosting();
    }

    // Setup button event handler which posts the entered message to Parse
    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 = ParseObject.create("Message");
                message.put(USER_ID_KEY, ParseUser.getCurrentUser().getObjectId());
                message.put(BODY_KEY, data);
                message.saveInBackground(new SaveCallback() {
                    @Override
                    public void done(ParseException e) {
                        if (!isValid()) return;
                    	Toast.makeText(ChatActivity.this, "Successfully created message on Parse",
                             Toast.LENGTH_SHORT).show();
                    }
                });
                etMessage.setText(null);
            }
        });
    }
}

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. Add ListView to Chat 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="@android:color/white"
  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: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/ivProfileOther"
        android:contentDescription="@string/profile_other"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@mipmap/ic_launcher" />
    <TextView
        android:textSize="18sp"
        android:id="@+id/tvBody"
        android:padding="20dp"
        android:lines="3"
        android:layout_marginEnd="64dp"
        android:layout_width="match_parent"
        android:layout_height="64dp">
    </TextView>
    <ImageView
        android:id="@+id/ivProfileMe"
        android:contentDescription="@string/profile_me"
        android:layout_marginStart="-64dp"
        android:layout_width="64dp"
        android:layout_height="64dp"
        android:src="@mipmap/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 let's create a Message.java class which will extend from ParseObject. This model class will provide message data for the ListView and will be used to retrieve and save messages to Parse.

@ParseClassName("Message")
public class Message extends ParseObject {
    public static final String USER_ID_KEY = "userId";
    public static final String BODY_KEY = "body";

    public String getUserId() {
        return getString(USER_ID_KEY);
    }

    public String getBody() {
        return getString(BODY_KEY);
    }

    public void setUserId(String userId) {
        put(USER_ID_KEY, userId);
    }

    public void setBody(String body) {
        put(BODY_KEY, 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 {
	// ...
	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);
	}
}

Finally, we refactor ChatActivity and rename the references to the model keys

...
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 View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String data = etMessage.getText().toString();
                ParseObject message = ParseObject.create("Message");
                message.put(**Message.USER_ID_KEY**, ParseUser.getCurrentUser().getObjectId());
                message.put(**Message.BODY_KEY**, 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(null);
            }
        });
    }
...

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. We'll be using the open source Picassolibrary to load profile images. Add dependency for this library to the app/build.gradle file.

...
dependencies {
    compile fileTree(dir: 'libs', include: '*.jar')
    compile 'com.android.support:appcompat-v7:22.2.1'
    compile 'com.squareup.picasso:picasso:2.5.2'
}

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.imageOther = (ImageView)convertView.findViewById(R.id.ivProfileOther);
            holder.imageMe = (ImageView)convertView.findViewById(R.id.ivProfileMe);
            holder.body = (TextView)convertView.findViewById(R.id.tvBody);
            convertView.setTag(holder);
        }
        final 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.imageMe.setVisibility(View.VISIBLE);
            holder.imageOther.setVisibility(View.GONE);
            holder.body.setGravity(Gravity.CENTER_VERTICAL | Gravity.RIGHT);
        } else {
            holder.imageOther.setVisibility(View.VISIBLE);
            holder.imageMe.setVisibility(View.GONE);
            holder.body.setGravity(Gravity.CENTER_VERTICAL | Gravity.LEFT);
        }
        final ImageView profileView = isMe ? holder.imageMe : holder.imageOther;
        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 imageOther;
        public ImageView imageMe;
        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:

public class ChatActivity extends AppCompatActivity {
...
    ListView lvChat;
    ArrayList<Message> mMessages;
    ChatListAdapter mAdapter;
    // Keep track of initial load to scroll to the bottom of the ListView
    boolean mFirstLoad;
	
    // Setup message field and posting
    void setupMessagePosting() {
        // Find the text field and button
        etMessage = (EditText) findViewById(R.id.etMessage);
        btSend = (Button) findViewById(R.id.btSend);
        lvChat = (ListView) findViewById(R.id.lvChat);
        mMessages = new ArrayList<>();
        // Automatically scroll to the bottom when a data set change notification is received and only if the last item is already visible on screen. Don't scroll to the bottom otherwise.
        lvChat.setTranscriptMode(1);
        mFirstLoad = true;
        final String userId = ParseUser.getCurrentUser().getObjectId();
        mAdapter = new ChatListAdapter(ChatActivity.this, userId, mMessages);
        lvChat.setAdapter(mAdapter);
        // When send button is clicked, create message object on Parse
        btSend.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                String data = etMessage.getText().toString();
                ParseObject message = ParseObject.create("Message");
                message.put(Message.USER_ID_KEY, userId);
                message.put(Message.BODY_KEY, data);
                message.saveInBackground(new SaveCallback() {
                    @Override
                    public void done(ParseException e) {
                        Toast.makeText(ChatActivity.this, "Successfully created message on Parse",
                                Toast.LENGTH_SHORT).show();
                        refreshMessages();
                    }
                });
                etMessage.setText(null);
            }
        });
    }

    // Query messages from Parse so we can load them into the chat adapter
    void refreshMessages() {
        // TODO:
    }
...
}

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:

public class ChatActivity extends AppCompatActivity {
...
    static final int MAX_CHAT_MESSAGES_TO_SHOW = 50;
...
    // Query messages from Parse so we can load them into the chat adapter
    void refreshMessages() {
        // 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
                    // Scroll to the bottom of the list on initial load
                    if (mFirstLoad) {
                        lvChat.setSelection(mAdapter.getCount() - 1);
                        mFirstLoad = false;
                    }
                } else {
                    Log.e("message", "Error Loading Messages" + e);
                }
            }
        });
    }
}

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 the more efficient "push" technique for refreshing new messages - but will work for the purposes of this simple project.

...

// Create a handler which can run code periodically
static final int POLL_INTERVAL = 100; // milliseconds
Handler mHandler = new Handler();  // android.os.Handler
Runnable mRefreshMessagesRunnable = new Runnable() {
    @Override
    public void run() {
       refreshMessages();
       mHandler.postDelayed(this, POLL_INTERVAL);
    }
};

...

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_chat);
    if (ParseUser.getCurrentUser() != null) {
        startWithCurrentUser();
    } else {
    	login();
    }
    mHandler.postDelayed(mRefreshMessagesRunnable, POLL_INTERVAL);
}

See the repeating periodic tasks guide to learn more about the handler.

13. Final AndroidManifest.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.android.simplechat">

    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <application
        android:name=".ChatApplication"
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".ChatActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <meta-data
            android:name="com.parse.APPLICATION_ID"
            android:value="{APPLICATION_ID}" />
        <meta-data
            android:name="com.parse.CLIENT_KEY"
            android:value="{CLIENT_KEY}" />
    </application>
</manifest>

14. Final Output

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