Jetpack Compose, custom cursor position in TextField

Question

How can I set the cursor in a random position on a TextField when it it get focus? The equivalent of editText.setSelection(position) with the classic android view system.

This is the code I am using to have an edit text automatically receive the focus when it is added to the screen. I would like to be able to move the cursor from the default position which is 0

val (getText, setText) = remember { mutableStateOf("hello") }
AutofocusEditText(
    text = getText,
    setText = setText
)
    
...

@Composable
private fun AutofocusEditText(
    text: String,
    setText : (String) -> Unit
) {
    val focusState = remember { mutableStateOf(FocusState.Inactive) }
    val focusRequester = FocusRequester()
    val focusModifier = Modifier.focus()
    Row(
        modifier = Modifier.focusObserver { newFocusValue -> focusState.value = newFocusValue }
    ) {
        val focusRequesterModifier =
            Modifier.focusRequester(focusRequester)

        TextField(
            value = text,
            modifier = focusModifier.then(focusRequesterModifier),
            backgroundColor = Color.Transparent,
            onValueChange = setText,
            keyboardOptions = KeyboardOptions.Default.copy(
                imeAction = ImeAction.Done
            ),
            onImeActionPerformed = { action, softKeyboardController ->
                if (action == ImeAction.Done) {
                    softKeyboardController?.hideSoftwareKeyboard()
                }
            }
        )
    }
    onActive {
        focusRequester.requestFocus()
    }
}

Answer 1

You have to use the TextFieldValue version of TextField.

@Composable
fun TextField(
    value: TextFieldValue,
    onValueChange: (TextFieldValue) -> Unit,
    /* ... */) {/* Impl */}

Code examples: EDIT: Compose Version 1.1.1 (13.04.22)

enum class CursorSelectionBehaviour {
    START, END, SELECT_ALL
}

@Composable
fun AutofocusTextFieldExample(
    initValue: String,
    behaviour: CursorSelectionBehaviour = CursorSelectionBehaviour.END
) {
    val direction = LocalLayoutDirection.current
    var tfv by remember {
        val selection = when (behaviour) {
            CursorSelectionBehaviour.START -> {
                if (direction == Ltr) TextRange.Zero else TextRange(initValue.length)
            }
            CursorSelectionBehaviour.END -> {
                if (direction == Ltr) TextRange(initValue.length) else TextRange.Zero
            }
            CursorSelectionBehaviour.SELECT_ALL -> TextRange(0, initValue.length)
        }
        val textFieldValue = TextFieldValue(text = initValue, selection = selection)
        mutableStateOf(textFieldValue)
    }
    val focusRequester = remember { FocusRequester.Default }
    TextField(
        modifier = Modifier.focusRequester(focusRequester),
        value = tfv,
        onValueChange = { tfv = it }
    )
    LaunchedEffect(Unit) {
        focusRequester.requestFocus()
    }
}

OLD (04.01.21):

    @Composable
    fun AutoFocusingText() {
        val textState = remember { mutableStateOf(TextFieldValue()) }
        val focusState = remember { mutableStateOf(FocusState.Inactive) }
        val focusRequester = FocusRequester()
        val focusModifier = Modifier.focus()
        Row(
            modifier = Modifier.focusObserver { focusState.value = it }
        ) {
            val focusRequesterModifier = Modifier.focusRequester(focusRequester)
            TextField(
                modifier = focusModifier.then(focusRequesterModifier),
                value = textState.value,
                onValueChange = { value: TextFieldValue ->
                    textState.value = value
                }
            )
        }
        onActive {
            focusRequester.requestFocus()
        }
    }

If you have a non-empty string as an initial value you have to change the selection manually. Replace the empty TextFieldValue with: TextFieldValue(text = value, selection = TextRange(value.length, value.length))

When you want to extract the value like it is in your code. You either add the current selection as a parameter or extract it combined with the TextFieldValue. Otherwise, if the user edits in the middle of the text the cursor jumps back to the end on the next onValueChanged.