Out of curiosity I used ChatGPT to generate some documentation for text editor fields in Android with Jetpack Compose.

I didn’t validate the contents, and the links are incorrect–but it’s a damned interesting use case for documenting your code.

My initial prompt was:

Write documentation that covers text editor fields in Android and Jetpack Compose.

I’d like the documentation to have the following format:

1. A brief introductory section that describes the purpose of text editor fields.

2. An overview of the various components that make up our various text editor fields.

3. A section which covers common use cases, grouped by use cases: what’s necessary to start things up and shut things down (if applicable), followed by common use cases, followed by more complex examples.

4. A section that provides a brief API summary.

With just a little bit of prompting I got it to generate the following documentation.

Text Editor Fields in Android and Jetpack Compose

Introduction

Text fields are one of the most essential components in any Android application, allowing users to enter and edit text. Whether it's a simple form, a chat application, or a complex note-taking app, text fields help users interact with your app effectively. Jetpack Compose simplifies working with text fields by offering declarative, flexible, and state-driven UI components that seamlessly integrate with input handling and keyboard interactions.

Components of Text Editor Fields

Text editor fields in Android consist of multiple components, each contributing to their functionality:

• TextField: The fundamental input component in Jetpack Compose, providing a basic text entry interface.
• OutlinedTextField: A variant of TextField with an outlined border, useful for visually distinguishing input fields.
• BasicTextField: A lower-level text field that allows full customization of the input UI.
• Keyboard Options: Configurable settings to control keyboard behavior, including input type, capitalization, and actions.
• Visual Transformation: Used to modify the display of entered text (e.g., password masking).
• TextFieldValue: A structured representation of text state, including selection and composition data.
• Input Validation: Custom logic to ensure correct input formatting and constraints.
• Modifiers: Used to style, size, and position text fields within a UI layout.

Managing Text Input with Mutable State

To handle user input dynamically, text fields use mutable state to store their values. This allows real-time updates and validation while maintaining composability.

Why Use a Mutable String?

Using a mutable string stored in remember and mutableStateOf ensures that the UI correctly reflects changes as users type. This enables:

• Real-time updates: The UI refreshes automatically when the state changes.
• State persistence: The text value persists across recompositions, maintaining the user’s input.
• Controlled modifications: We can modify input dynamically before updating the state.

Example:

var text by remember { mutableStateOf("") }
TextField(
    value = text,
    onValueChange = { text = it },
    label = { Text("Enter text") }
)

Restricting User Input

A mutable state also allows us to control and validate input dynamically. For instance, limiting input to numeric values:

var text by remember { mutableStateOf("") }
TextField(
    value = text,
    onValueChange = {
        if (it.all { char -> char.isDigit() }) {
            text = it
        }
    },
    label = { Text("Enter numbers only") },
    keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number)
)

This ensures that users can only enter numeric characters while preventing invalid input from being stored.

Common Use Cases

Initialization and Cleanup

To start using a text field in Jetpack Compose:

var text by remember { mutableStateOf("") }
TextField(
    value = text,
    onValueChange = { text = it },
    label = { Text("Enter text") }
)

No explicit shutdown is required, but clearing the state or dismissing the keyboard can be done when needed:

text = ""  // Clears the text
focusManager.clearFocus() // Hides the keyboard

Basic Text Input

For simple text input:

TextField(
    value = text,
    onValueChange = { text = it },
    keyboardOptions = KeyboardOptions.Default
)

Handling Keyboard Actions

To customize keyboard behavior, such as reacting to the "Done" action:

TextField(
    value = text,
    onValueChange = { text = it },
    keyboardOptions = KeyboardOptions.Default.copy(
        imeAction = ImeAction.Done
    ),
    keyboardActions = KeyboardActions(
        onDone = { focusManager.clearFocus() }
    )
)

Input Validation

Ensuring valid input before submission:

val isValid = text.length >= 5
TextField(
    value = text,
    onValueChange = { text = it },
    isError = !isValid,
    label = { Text("Enter at least 5 characters") }
)

Complex Example: Password Input with Masking

var password by remember { mutableStateOf("") }
var passwordVisible by remember { mutableStateOf(false) }

TextField(
    value = password,
    onValueChange = { password = it },
    visualTransformation = if (passwordVisible) VisualTransformation.None else PasswordVisualTransformation(),
    trailingIcon = {
        val image = if (passwordVisible) Icons.Default.Visibility else Icons.Default.VisibilityOff
        IconButton(onClick = { passwordVisible = !passwordVisible }) {
            Icon(imageVector = image, contentDescription = "Toggle Password Visibility")
        }
    }
)

API Summary

The following Jetpack Compose API components are commonly used when working with text fields:

• TextField: A standard text input field.
• OutlinedTextField: A text input with an outlined border.
• BasicTextField: A minimalistic text field for custom implementations.
• KeyboardOptions: Defines keyboard behavior and input constraints.
• KeyboardActions: Handles keyboard interactions.
• VisualTransformation: Controls how text is displayed (e.g., password masking).
• Modifier: Customizes the look and feel of text fields.

For more detailed information, refer to the Jetpack Compose Documentation.

This guide provides an overview of text editor fields in Android and Jetpack Compose, covering basic to advanced usage scenarios.

As an aside, I’m not at all worried about using ChatGPT or LLMs in general taking jobs from tech writers or programmers, mostly because this is the sort of work no-one currently does. So it’s a good use case of something we need more of, that people aren’t currently doing.