> ## Documentation Index
> Fetch the complete documentation index at: https://cometchat-013b37f0.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Building A One To One/Group Chat Experience

The **One-to-One Chat** feature provides a streamlined **direct messaging interface**, making it ideal for **support chats, dating apps, and private messaging platforms**. This setup eliminates distractions by focusing solely on a **dedicated chat window**.

***

## **User Interface Preview**

<Frame>
  <img src="https://mintcdn.com/cometchat-013b37f0/qPj1u-01bVacwjS9/images/c401197a-chat_experience_one_on_one-5b74b8c178c83ecb0a8879e898fcb854.png?fit=max&auto=format&n=qPj1u-01bVacwjS9&q=85&s=6ab07aaa9481e25c69ba22fc5f972c22" width="1440" height="833" data-path="images/c401197a-chat_experience_one_on_one-5b74b8c178c83ecb0a8879e898fcb854.png" />
</Frame>

### **Key Components**

1. **Chat Header** – Displays user/group name, profile image, and status.
2. **Message List** – Shows chat history and new messages.
3. **Message Composer** – Allows users to send messages, media, and reactions.

***

## **Step-by-Step Guide**

### **Step 1: Set Up Message Activity**

Create an Activity - `MessageActivity.kt`  to manage and display the chat UI.

#### **Layout**

Define the layout using CometChat UI Kit components:

```xml activity_message.xml theme={null}
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MessageActivity">

    <!-- Message Header -->
    <com.cometchat.chatuikit.messageheader.CometChatMessageHeader
        android:id="@+id/message_header"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <!-- Message List -->
    <com.cometchat.chatuikit.messagelist.CometChatMessageList
        android:id="@+id/message_list"
        android:layout_width="0dp"
        android:layout_height="0dp"
        app:layout_constraintTop_toBottomOf="@id/message_header"
        app:layout_constraintBottom_toTopOf="@id/message_composer"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

    <!-- Message Composer -->
    <com.cometchat.chatuikit.messagecomposer.CometChatMessageComposer
        android:id="@+id/message_composer"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>
```

#### **Activity**

<Tabs>
  <Tab title="Kotlin">
    ```kotlin MessageActivity.kt theme={null}
    import android.os.Bundle
    import android.util.Log
    import android.widget.Toast
    import androidx.activity.enableEdgeToEdge
    import androidx.appcompat.app.AppCompatActivity
    import com.cometchat.chat.core.CometChat
    import com.cometchat.chat.exceptions.CometChatException
    import com.cometchat.chat.models.Group
    import com.cometchat.chat.models.User
    import com.cometchat.chatuikit.messagecomposer.CometChatMessageComposer
    import com.cometchat.chatuikit.messageheader.CometChatMessageHeader
    import com.cometchat.chatuikit.messagelist.CometChatMessageList

    class MessageActivity : AppCompatActivity() {
        private lateinit var messageHeader: CometChatMessageHeader
        private lateinit var messageList: CometChatMessageList
        private lateinit var messageComposer: CometChatMessageComposer

        private var uid: String? = null
        private var guid: String? = null

        private val TAG = "MessageActivity"

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            enableEdgeToEdge()
            setContentView(R.layout.activity_message)

            initializeViews()
            setupChat()
            setupHeaderBackButton()
        }

        private fun initializeViews() {
            messageHeader = findViewById(R.id.message_header)
            messageList = findViewById(R.id.message_list)
            messageComposer = findViewById(R.id.message_composer)
        }

        private fun setupChat() {
            uid = intent.getStringExtra("uid")
            guid = intent.getStringExtra("guid")

            when {
                uid != null -> setupUserChat(uid!!)
                guid != null -> setupGroupChat(guid!!)
                else -> {
                    Log.e(TAG, "No user ID or group ID provided")
                    showError("Missing user ID or group ID")
                    finish()
                }
            }
        }

        private fun setupUserChat(userId: String) {
            CometChat.getUser(userId, object : CometChat.CallbackListener<User>() {
                override fun onSuccess(user: User) {
                    Log.d(TAG, "Successfully loaded user: ${user.uid}")
                    messageHeader.setUser(user)
                    messageList.setUser(user)
                    messageComposer.setUser(user)
                }

                override fun onError(e: CometChatException?) {
                    Log.e(TAG, "Error loading user: ${e?.message}")
                    showError("Could not find user: ${e?.message}")
                    finish()
                }
            })
        }

        private fun setupGroupChat(groupId: String) {
            CometChat.getGroup(groupId, object : CometChat.CallbackListener<Group>() {
                override fun onSuccess(group: Group) {
                    Log.d(TAG, "Successfully loaded group: ${group.guid}")
                    messageHeader.setGroup(group)
                    messageList.setGroup(group)
                    messageComposer.setGroup(group)
                }

                override fun onError(e: CometChatException?) {
                    Log.e(TAG, "Error loading group: ${e?.message}")
                    showError("Could not find group: ${e?.message}")
                    finish()
                }
            })
        }

        private fun setupHeaderBackButton() {
            messageHeader.setOnBackButtonPressed {
                finish()
            }
        }

        private fun showError(message: String) {
            Toast.makeText(this, message, Toast.LENGTH_SHORT).show()
        }
    }
    ```
  </Tab>

  <Tab title="Java">
    ```java MessageActivity.java theme={null}
    import android.os.Bundle;
    import android.util.Log;
    import android.widget.Toast;

    import androidx.appcompat.app.AppCompatActivity;

    import com.cometchat.chat.core.CometChat;
    import com.cometchat.chat.exceptions.CometChatException;
    import com.cometchat.chat.models.Group;
    import com.cometchat.chat.models.User;
    import com.cometchat.chatuikit.messagecomposer.CometChatMessageComposer;
    import com.cometchat.chatuikit.messageheader.CometChatMessageHeader;
    import com.cometchat.chatuikit.messagelist.CometChatMessageList;

    public class MessageActivity extends AppCompatActivity {

        private static final String TAG = "MessageActivity";

        private CometChatMessageHeader messageHeader;
        private CometChatMessageList messageList;
        private CometChatMessageComposer messageComposer;

        private String uid;
        private String guid;

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            getWindow().setDecorFitsSystemWindows(false); // enableEdgeToEdge()
            setContentView(R.layout.activity_message);

            initializeViews();
            setupChat();
            setupHeaderBackButton();
        }

        private void initializeViews() {
            messageHeader = findViewById(R.id.message_header);
            messageList = findViewById(R.id.message_list);
            messageComposer = findViewById(R.id.message_composer);
        }

        private void setupChat() {
            uid = getIntent().getStringExtra("uid");
            guid = getIntent().getStringExtra("guid");

            if (uid != null) {
                setupUserChat(uid);
            } else if (guid != null) {
                setupGroupChat(guid);
            } else {
                Log.e(TAG, "No user ID or group ID provided");
                showError("Missing user ID or group ID");
                finish();
            }
        }

        private void setupUserChat(String userId) {
            CometChat.getUser(userId, new CometChat.CallbackListener<User>() {
                @Override
                public void onSuccess(User user) {
                    Log.d(TAG, "Successfully loaded user: " + user.getUid());
                    messageHeader.setUser(user);
                    messageList.setUser(user);
                    messageComposer.setUser(user);
                }

                @Override
                public void onError(CometChatException e) {
                    Log.e(TAG, "Error loading user: " + (e != null ? e.getMessage() : "Unknown error"));
                    showError("Could not find user: " + (e != null ? e.getMessage() : ""));
                    finish();
                }
            });
        }

        private void setupGroupChat(String groupId) {
            CometChat.getGroup(groupId, new CometChat.CallbackListener<Group>() {
                @Override
                public void onSuccess(Group group) {
                    Log.d(TAG, "Successfully loaded group: " + group.getGuid());
                    messageHeader.setGroup(group);
                    messageList.setGroup(group);
                    messageComposer.setGroup(group);
                }

                @Override
                public void onError(CometChatException e) {
                    Log.e(TAG, "Error loading group: " + (e != null ? e.getMessage() : "Unknown error"));
                    showError("Could not find group: " + (e != null ? e.getMessage() : ""));
                    finish();
                }
            });
        }

        private void setupHeaderBackButton() {
            messageHeader.setOnBackButtonPressed(() -> finish());
        }

        private void showError(String message) {
            Toast.makeText(this, message, Toast.LENGTH_SHORT).show();
        }
    }
    ```
  </Tab>
</Tabs>

<Warning>
  You must use an activity that supports the **lifecycle** API, such as:

  * `AppCompatActivity`
  * `ComponentActivity`
  * `FragmentActivity`

  This is necessary to properly manage the **UI Kit's lifecycle events**.
</Warning>

***

### **Step 2: Update MainActivity**

Update the `MainActivity` to navigate to the `MessageActivity`:

<Tabs>
  <Tab title="Kotlin">
    ```kotlin MainActivity.kt theme={null}
    import android.os.Bundle
    import android.util.Log
    import androidx.activity.ComponentActivity
    import androidx.activity.enableEdgeToEdge
    import com.cometchat.chat.core.CometChat
    import com.cometchat.chat.exceptions.CometChatException
    import com.cometchat.chat.models.User
    import com.cometchat.chatuikit.shared.cometchatuikit.CometChatUIKit
    import com.cometchat.chatuikit.shared.cometchatuikit.UIKitSettings

    class MainActivity : ComponentActivity() {

        private val TAG = "MainActivity"

        private val appID = "APP_ID" // Replace with your App ID
        private val region = "REGION" // Replace with your App Region
        private val authKey = "AUTH_KEY" // Replace with your Auth Key or leave blank if you are authenticating using Auth Token

        private val uiKitSettings = UIKitSettings.UIKitSettingsBuilder()
            .setRegion(region)
            .setAppId(appID)
            .setAuthKey(authKey)
            .subscribePresenceForAllUsers()
            .build()

        override fun onCreate(savedInstanceState: Bundle?) {
            super.onCreate(savedInstanceState)
            enableEdgeToEdge()

            CometChatUIKit.init(this, uiKitSettings, object : CometChat.CallbackListener<String?>() {
                override fun onSuccess(successString: String?) {

                    Log.d(TAG, "Initialization completed successfully")

                    loginUser()
                }

                override fun onError(e: CometChatException?) {}
            })
        }

        private fun loginUser() {
            CometChatUIKit.login("cometchat-uid-1", object : CometChat.CallbackListener<User>() {
                override fun onSuccess(user: User) {

                    // Launch One-to-One or Group Chat Screen
                     val intent = Intent(this@MainActivity, MessageActivity::class.java)
                     intent.putExtra("uid", "cometchat-uid-1")
                     startActivity(intent)
                }

                override fun onError(e: CometChatException) {
                    // Handle login failure (e.g. show error message or retry)
                    Log.e("Login", "Login failed: ${e.message}")
                }
            })
        }
    }
    ```
  </Tab>

  <Tab title="Java">
    ```java MainActivity.java theme={null}
    import android.content.Intent;
    import android.os.Bundle;
    import android.util.Log;
    import androidx.activity.ComponentActivity;
    import com.cometchat.chat.core.CometChat;
    import com.cometchat.chat.exceptions.CometChatException;
    import com.cometchat.chat.models.User;
    import com.cometchat.chatuikit.shared.cometchatuikit.CometChatUIKit;
    import com.cometchat.chatuikit.shared.cometchatuikit.UIKitSettings;

    public class MainActivity extends ComponentActivity {

        private static final String TAG = "MainActivity";

        private final String appID = "APP_ID"; // Replace with your App ID
        private final String region = "REGION"; // Replace with your App Region
        private final String authKey = "AUTH_KEY"; // Replace with your Auth Key

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            getWindow().setDecorFitsSystemWindows(false); // Equivalent to enableEdgeToEdge()

            UIKitSettings uiKitSettings = new UIKitSettings.UIKitSettingsBuilder()
                    .setRegion(region)
                    .setAppId(appID)
                    .setAuthKey(authKey)
                    .subscribePresenceForAllUsers()
                    .build();

            CometChatUIKit.init(this, uiKitSettings, new CometChat.CallbackListener<String>() {
                @Override
                public void onSuccess(String success) {
                    Log.d(TAG, "Initialization completed successfully");
                    loginUser();
                }

                @Override
                public void onError(CometChatException e) {
                    Log.e(TAG, "Initialization failed: " + (e != null ? e.getMessage() : "Unknown error"));
                }
            });
        }

        private void loginUser() {
            CometChatUIKit.login("cometchat-uid-1", new CometChat.CallbackListener<User>() {
                @Override
                public void onSuccess(User user) {
                    Log.d(TAG, "Login successful for user: " + user.getUid());

                    // Launch One-to-One or Group Chat Screen
                     Intent intent = new Intent(MainActivity.this, MessageActivity.class);
                     intent.putExtra("uid", "cometchat-uid-1");
                     startActivity(intent);
                }

                @Override
                public void onError(CometChatException e) {
                    Log.e("Login", "Login failed: " + (e != null ? e.getMessage() : "Unknown error"));
                }
            });
        }
    }
    ```
  </Tab>
</Tabs>

***

## **Running the Project**

Once the components are configured, build and run the app:

```sh theme={null}
gradle build
```

Ensure you've added the necessary permissions and initialized CometChat in your `Application` class.

***

## **Next Steps**

### **Enhance the User Experience**

* **[Advanced Customizations](/ui-kit/android/theme-introduction)** – Personalize the chat UI to align with your brand.

***