Create a Mention Feature (@mention) in a TextField with Flutter

Chapter 1: Introduction: Overview of the Mention Functionality and Introduction to Flutter

The mention functionality (@mention), used in various fields such as social media, communities, and development platforms, provides a more convenient and efficient way of communication between users. In this chapter, we will briefly discuss the concept of the mention functionality and how to create a TextField widget with added mention capability using Flutter.

1.1 What is the mention functionality (@mention)?

The mention functionality is a feature that allows users to specifically tag or reference other users by attaching the '@' symbol in front of their usernames, thus facilitating smoother interactions with specific users. For example, on Twitter, by entering a user's username accompanied by the '@' symbol, you can send them a message or invite them to a conversation.

1.2 Introduction to Flutter

Flutter is an open-source mobile application development framework developed by Google, enabling the development of iOS and Android mobile applications using a single codebase. It allows for quick implementation of rich user interfaces (UI) and offers various widgets and plugins to add diverse functionalities.

1.3 Objective of Implementing the Mention Functionality in a TextField

In this article, we will give a step-by-step explanation on how to create a TextField widget with mention functionality using Flutter. In the final widget, when the user enters the '@' symbol, a pre-registered list of users is displayed, allowing the user to easily compose text mentioning a selected user.

Now, let's proceed to the next chapter, where we will learn how to initiate a Flutter project and set up the basic structure of the MentionableTextField widget.

Chapter 2: Setting Up the Basic Structure: Creating the MentionableTextField Widget

In this chapter, we will cover the process of setting up the basic structure required to create a TextField with added mention functionality. First, let's create the MentionableTextField widget and set up the necessary state management code.

2.1 Creating the MentionableTextField Widget

Follow these steps to create the MentionableTextField widget:

1. Create a new Stateless widget called MentionableTextField.
2. Initialize the widget with a TextField controller that stores the data needed to display the list of selected users and user names.
3. Set up the necessary styles and arguments for MentionableTextField.
4. In the build method, define how to display the list of users and the TextField.

Here is a basic code example of the MentionableTextField widget:

<code class="language-dart">
class MentionableTextField extends StatelessWidget {
  final TextEditingController controller;
  final List<String> userNames;

  MentionableTextField({
    required this.controller,
    required this.userNames,
  });

  @override
  Widget build(BuildContext context) {
    return Column(
      children: [
        // Implement the user list UI
        // Implement the TextField UI
      ],
    );
  }
}
</code>

2.2 Setting Up State Management

MentionableTextField has a state that changes depending on user input, such as showing or hiding the list of users. To manage this state, we will use Flutter's StatefulWidget and State classes.

• Create a StatefulWidget that inherits MentionableTextField.
  Example: class _MentionableTextFieldState extends State<MentionableTextField> {...}
• Add variables for state management and initialize them in the initState method, making them initially hidden.
• Implement the logic to show or hide the user list within the _MentionableTextFieldState class.

Additionally, we will use the onChanged listener of the TextField widget to add mention functionality logic, which will be triggered after the user has entered text. With the onChanged event, we can detect when the user has entered the '@' symbol.

So far, we have set up the basic structure. In the next chapter, we will explore implementing the user search and selection interface.

Chapter 3: Adding Mention Functionality: Implementing the User Search and Selection Interface

Now that we have set up the basic structure, let's implement the user search and selection interface. In this process, we will create a UI that displays search results to the user and write the logic for handling the selected result from the search.

3.1 Implementing the User Search UI

Create a UI component to display the list of users when utilizing the mention feature. Render the user list using ListView.builder. Refer to the example code below:

<code class="language-dart">
Column(
  children: [
    Visibility(
      visible: _showUsers,
      child: Container(
        height: 200,
        child: ListView.builder(
          itemCount: userNames.length,
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              title: Text(userNames[index]),
              onTap: () {
                // Implement user selection logic
              },
            );
          },
        ),
      ),
    ),
    // Implement TextField UI
  ],
)
</code>

_showUsers is a bool type state variable that determines whether the user list will be displayed and is initialized as false in the initState method.

3.2 Detecting Mention Input in the TextField

To track when the user has entered the '@' symbol, you need to use the onChanged callback function of TextField. Using the onChanged callback, call a method every time the text in TextField changes, and set it to display the user list when the '@' symbol appears.

<code class="language-dart">
TextField(
  controller: controller,
  onChanged: (text) {
    if (text.endsWith('@')) {
      // Implement user list display logic
      setState(() {
        _showUsers = true;
      });
    }
  },
)
</code>

3.3 Implementing the User Selection Logic

When a user selects a user from the list, insert the selected user as mention text and hide the list. This operation can be done in the onTap callback function of ListTile in ListView.builder. Write the logic to add the selected username to the existing TextField text and hide the user list.

<code class="language-dart">
ListTile(
  title: Text(userNames[index]),
  onTap: () {
    setState(() {
      controller.text += '${userNames[index]} ';
      controller.selection = TextSelection.collapsed(offset: controller.text.length);
      _showUsers = false;
    });
  },
)
</code>

By doing so, the user search and selection interface is implemented. In the next chapter, we will explain how to apply the style for mention text and the overall TextField UI design.

Chapter 4: Applying Mention Style and TextField UI Design

In this chapter, we will explain how to apply the style for mention text within the TextField that includes the mention functionality and how to complete the overall TextField UI design.

4.1 Applying Mention Text Style

The TextSpan and RichText widgets, which allow specifying text styles, can be used so that not all text has the same style applied, and only the mention part starting with the '@' symbol has a different style applied. Use conditional statements to analyze the text components and specify styles.

Please refer to the example code below and replace the implemented TextField with RichText to apply mention style.

<code class="language-dart">
// Example of mention text style
RichText(
  text: TextSpan(
    children: [
      for (var part in controller.text.split(' '))
        TextSpan(
          text: '$part ',
          style: part.startsWith('@') 
            ? TextStyle(color: Colors.blue) 
            : TextStyle(color: Colors.black),
        ),
    ],
  ),
)
</code>

As seen in the code, the example uses changing the text color of the mention part starting with the '@' symbol to blue. Add desired style elements to appropriately emphasize mention text.

4.2 Handling Mention Text Selection and Movement Actions

In a TextField with added mention functionality, it is important to handle appropriate actions when users select text or move the cursor. To do this, use the EditableText widget, which manages keyboard and selection actions for TextField. You can restrict actions when the cursor enters the mention text or adjust it to select the entire mention.

4.3 Completing the Overall TextField UI Design

Finally, we will look at ways to add and reference design options for the overall TextField appearance. Use the InputDecoration class to include various style elements in the TextField. As an example, apply the following properties:

• Border: OutlineInputBorder
• Hint text: "Please write a message."
• Padding and content alignment: Apply margins, text alignment, etc.

Through these methods, you can complete the UI design of the TextField with mention functionality added.

Now, you can use the finished MentionableTextField widget to add a text field with mention functionality wherever needed. This allows you to create effective applications that provide smooth interaction between users, and you can add various style and feature adjustments as needed.

Chapter 5: Performance Optimization and Usability Improvement

In this chapter, we will explain how to optimize performance and improve the usability of the TextField widget with mention functionality. Performance optimization enhances the responsiveness and efficiency of the app, while the usability improvement enhances the user experience (UX).

5.1 Performance Optimization

If the mention functionality is in a single ListView or a small user list, performance issues may be minimal, but as the user list expands and more elements are added to the screen, performance problems can arise. To optimize performance, consider the following methods:

• **Paging**: When fetching user data from the server, apply paging to prevent loading too many items at once.
• **Lazy Loading**: Use ListView.builder to load only the necessary items when scrolling so users can retrieve only the data they need.
• **Caching**: If user data does not change frequently, temporarily store the user data within the app to reduce network calls.

5.2 Usability Improvement

To enhance the usability of the TextField with mention functionality, consider the following:

• **Text Styling**: Apply different text styling to mentioned usernames so users can easily distinguish them.
• **Mention Feature Indication**: Use a keyboard accessory view or a button to inform users that they can activate the mention feature by typing '@'.
• **Search Result Filtering**: When users type '@' and enter characters, have the list filtered in real-time to display only relevant users, making the search process more manageable.
• **Enter Key Behavior**: Implement logic to complete mention input and hide the user list when the Enter key is pressed to facilitate keyboard operations.

A TextField with implemented mention functionality, considering these performance optimization and usability improvements, will provide smooth interaction. This enhanced user experience will positively impact application usage and user acquisition.