Customizing Highlighted Text Color in Jetpack Compose TextField

Jetpack Compose, Google's modern toolkit for building Android user interfaces, empowers developers to create stunning, responsive, and customizable UI components. One of the frequently used components is the TextField, which allows users to input and edit text in applications. While the default TextField setup is sufficient for many use cases, customization is often necessary to match your app's design language. In this article, we’ll explore how to customize the highlighted text color in a TextField in Jetpack Compose.

Why Customize Highlighted Text Color?

The highlighted text color is the color applied to selected text within a TextField. Customizing this color can:

Enhance your app's branding by aligning with your color scheme.
Improve accessibility by ensuring adequate contrast for better readability.
Provide a more cohesive user experience by maintaining visual consistency across your app.

Jetpack Compose’s flexible TextField API makes it possible to achieve this customization with minimal effort.

Default Behavior of TextField Highlighting

By default, Jetpack Compose applies a system-defined color to the highlighted text in a TextField. This is suitable for general use but may not meet your specific design requirements. The highlighted text color is determined by the LocalTextSelectionColors composition local, which provides a TextSelectionColors instance.

@Composable
fun DefaultTextField() {
    TextField(
        value = "Jetpack Compose",
        onValueChange = {},
        label = { Text("Enter text") }
    )
}

In the default configuration, the highlighted text will use the default selection color provided by the system.

How to Customize Highlighted Text Color

Step 1: Understand `TextSelectionColors`

TextSelectionColors is a data class in Jetpack Compose that holds two color properties:

handleColor: The color of the selection handles.
backgroundColor: The color of the selection highlight (i.e., the background color of the selected text).

Step 2: Create a Custom `TextSelectionColors`

You can define your own TextSelectionColors to specify the backgroundColor for highlighted text and the handleColor for the selection handles.

val customTextSelectionColors = TextSelectionColors(
    handleColor = Color.Magenta, // Custom handle color
    backgroundColor = Color.Yellow // Custom highlight color
)

Step 3: Apply the Custom `TextSelectionColors`

To apply your custom selection colors, wrap your TextField in a CompositionLocalProvider and override the LocalTextSelectionColors composition local.

@Composable
fun CustomTextField() {
    CompositionLocalProvider(
        LocalTextSelectionColors provides customTextSelectionColors
    ) {
        TextField(
            value = "Jetpack Compose",
            onValueChange = {},
            label = { Text("Enter text") }
        )
    }
}

With this setup, the TextField will use your custom colors for both the selection highlight and the selection handles.

Example: Themed TextField Customization

To further integrate this customization into your app’s theme, you can define a TextSelectionColors instance in your theme setup. For example:

@Composable
fun MyAppTheme(content: @Composable () -> Unit) {
    val customTextSelectionColors = TextSelectionColors(
        handleColor = MaterialTheme.colorScheme.primary,
        backgroundColor = MaterialTheme.colorScheme.secondary.copy(alpha = 0.4f)
    )

    CompositionLocalProvider(
        LocalTextSelectionColors provides customTextSelectionColors
    ) {
        MaterialTheme {
            content()
        }
    }
}

You can then wrap your app’s content in the MyAppTheme composable to ensure consistent styling across all TextField components.

@Composable
fun MyApp() {
    MyAppTheme {
        Column(
            modifier = Modifier.padding(16.dp)
        ) {
            Text("Customized TextField")
            Spacer(modifier = Modifier.height(8.dp))
            CustomTextField()
        }
    }
}

Additional Tips for TextField Customization

Dynamic Color Adjustments: Use dynamic color adjustments to adapt the highlight color based on light or dark mode.

val customTextSelectionColors = TextSelectionColors(
    handleColor = if (isSystemInDarkTheme()) Color.White else Color.Black,
    backgroundColor = if (isSystemInDarkTheme()) Color.DarkGray else Color.LightGray
)

Testing Accessibility: Use tools like Accessibility Scanner to ensure the contrast ratio of your custom colors meets accessibility standards.
Preview Your Changes: Use Jetpack Compose Previews to validate your customization before running the app.
```
@Preview(showBackground = true)
@Composable
fun PreviewCustomTextField() {
    CustomTextField()
}
```

Conclusion

Customizing the highlighted text color in a TextField is a simple yet powerful way to enhance your app’s user experience and visual appeal. By leveraging Jetpack Compose’s TextSelectionColors and LocalTextSelectionColors, you can achieve seamless integration with your app’s design system.

With these tools at your disposal, you can ensure that every aspect of your app’s UI aligns perfectly with your brand and user needs. Experiment with different configurations to create a TextField experience that stands out!