选择 Jetpack Compose 中 TextField 的所有文本

Question

I'm using TextField component in Jetpack Compose. How to select all text when it receive focus?

Answer 1

In this case you should use TextFieldValue as state of your TextField , and when it receive focus, you set the selection using the TextFieldValue state.

val state = remember {
    mutableStateOf(TextFieldValue(""))
}
TextField(
    value = state.value,
    onValueChange = { text -> state.value = text },
    modifier = Modifier
        .onFocusChanged { focusState ->
            if (focusState.isFocused) {
                val text = state.value.text
                state.value = state.value.copy(
                    selection = TextRange(0, text.length)
                )
            }
        }
)

Here's the result:

Notice that depending on you're touching the cursor goes to the touched position instead of select the entire text. You can try to figure it out if this is a bug or a feature :)

Answer 2

@nglauber solution doesn't seems to work anymore.

Debugging shows that onFocusChanged is called before onValueChange and within one view life cycle. A selection changed during onFocusChanged has no effect on TextField , since it is overridden during onValueChange .

Here's a possible workaround:

var state by remember {
    mutableStateOf(TextFieldValue("1231"))
}
var keepWholeSelection by remember { mutableStateOf(false) }
if (keepWholeSelection) {
    // in case onValueChange was not called immediately after onFocusChanged
    // the selection will be transferred correctly, so we don't need to redefine it anymore
    SideEffect {
        keepWholeSelection = false
    }
}
TextField(
    value = state,
    onValueChange = { newState ->
        if (keepWholeSelection) {
            keepWholeSelection = false
            state = newState.copy(
                selection = TextRange(0, newState.text.length)
            )
        } else {
            state = newState
        }
    },
    modifier = Modifier
        .onFocusChanged { focusState ->
            if (focusState.isFocused) {
                val text = state.text
                state = state.copy(
                    selection = TextRange(0, text.length)
                )
                keepWholeSelection = true
            }
        }
)

I think it should be possible to make it easier, so I created this question on Compose issue tracker.

Answer 3

I didn't have 100% success with @nglauber answer. You should add a small delay and it works great. For example:

        val state = remember {
            mutableStateOf(TextFieldValue(""))
        }

        // get coroutine scope from composable
        val scope = rememberCoroutineScope()

        TextField(
            value = state.value,
            onValueChange = { text -> state.value = text },
            modifier = Modifier
                .onFocusChanged {
                    if (it.hasFocus) {
                        // start coroutine
                        scope.launch {
                            // add your preferred delay
                            delay(10)
                            val text = state.value.text
                            state.value = state.value.copy(
                                selection = TextRange(0, text.length)
                            )
                        }
                    }
                }
        )

Answer 4

I wrote a Modifier extension function that works in spite of bug pointed out by @Pylyp

fun Modifier.onFocusSelectAll(textFieldValueState: MutableState<TextFieldValue>): Modifier =
  composed(
    inspectorInfo = debugInspectorInfo {
      name = "textFieldValueState"
      properties["textFieldValueState"] = textFieldValueState
    }
  ) {
    var triggerEffect by remember {
      mutableStateOf<Boolean?>(null)
    }
    if (triggerEffect != null) {
      LaunchedEffect(triggerEffect) {
        val tfv = textFieldValueState.value
        textFieldValueState.value = tfv.copy(selection = TextRange(0, tfv.text.length))
      }
    }
    Modifier.onFocusChanged { focusState ->
      if (focusState.isFocused) {
        triggerEffect = triggerEffect?.let { bool ->
          !bool
        } ?: true
      }
    }
  }

usage

@Composable
fun SelectAllOnFocusDemo() {
  var tfvState = remember {
    mutableStateOf(TextFieldValue("initial text"))
  }
  TextField(
    modifier = Modifier.onFocusSelectAll(tfvState),
    value = tfvState.value,
    onValueChange = { tfvState.value = it },
  )
}