The TextField function in Jetpack Compose is a key composable that allows users to input text. It's very customizable and is built with many optional parameters to enhance the flexibility of the text input fields.
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Core Parameters:
value: TextFieldValue
Represents the current value of the TextField. It can be a simple string or a more complex object like TextFieldValue which holds both the text and the cursor position. This allows for more control over the behavior of the text field.
onValueChange: (TextFieldValue) -> Unit
A lambda that is called whenever the content of the TextField changes. It's important to update the state holding the text inside this function.
Customization Parameters:
modifier: Modifier
You can use Modifier to customize the appearance or behavior of the TextField. For example, you can add padding, change the size, or define its alignment.
enabled: Boolean
Controls whether the TextField is enabled or disabled. If you disable it, the user can't interact with it.
readOnly: Boolean
When set to true, the text can be selected and copied, but not edited. This is useful for displaying text that shouldn't be modified by the user.
textStyle: TextStyle
Defines how the text inside the TextField looks, such as the font size, color, and weight.
Visual Customization:
label: (@Composable () -> Unit)?
A composable that defines a label for the TextField, usually used to show the name of the field (e.g., "Username"). It appears inside the text field and moves above when the user types.
placeholder: (@Composable () -> Unit)?
A placeholder is shown when the TextField is empty, giving a hint to the user about what kind of input is expected.
leadingIcon and trailingIcon: (@Composable () -> Unit)?
Allows you to add icons or any composable before or after the input text, respectively. For example, you could place a search icon in the leadingIcon.
prefix and suffix: (@Composable () -> Unit)?
Similar to leading and trailing icons but more focused on text-like components, such as currency symbols (prefix) or units (suffix).
Error and Validation:
isError: Boolean
When set to true, it marks the text field as having an error. You can change the appearance of the field (e.g., showing a red border) when there is an error.
supportingText: (@Composable () -> Unit)?
Used to display additional supporting text below the TextField, like error messages or hints.
Text Transformation:
visualTransformation: VisualTransformation
This allows for modifying the displayed text without changing the actual value. For example, you can use PasswordVisualTransformation() to hide the characters of a password.
Keyboard and Input Behavior:
keyboardOptions: KeyboardOptions
Defines options for the software keyboard. You can specify the type of keyboard (e.g., numeric or text) or actions like "Done", "Next", or "Search".
keyboardActions: KeyboardActions
This lets you handle events like when the user presses "Enter" or "Done" on the keyboard, allowing for actions like submitting a form.
Line and Text Handling:
singleLine: Boolean
When set to true, the TextField only allows one line of input. This is used for fields like usernames or passwords.
maxLines: Int
Defines the maximum number of lines the text field can have. It defaults to Int.MAX_VALUE when singleLine is false.
minLines: Int
Defines the minimum number of lines the text field will display.
Shape and Colors:
shape: Shape
Specifies the shape of the TextField, like rounded corners. You can use predefined shapes or define your own.
colors: TextFieldColors
Allows you to customize the colors of different elements of the TextField, such as the text, cursor, background, and more.
Interaction Source:
interactionSource: MutableInteractionSource?
Tracks the user's interaction with the TextField, such as focus or clicks. You can use this to add animations or other effects based on user interaction.