更改光标位置并在Jetpack Compose中强制TextField的SingleLine [英] Change Cursor Position and force SingleLine of TextField in Jetpack Compose

问题描述

找不到改变TextField光标位置并使之成为单行的方法.有人找到一种方法吗?

Couldn't find a way to change the cursor position of TextField and making it singleline. Someone find a way to do it?

目前，我正在使用最新的jetpack-compose 1.0.0-alpha03版本.

At this time, I'm using the latest jetpack-compose 1.0.0-alpha03 version.

推荐答案

要设置光标，您需要像这样设置TextFieldValue的选择:

To set the cursor you need to set the selection of the TextFieldValue like this:

@Composable
fun Content() {
    val initTargetIndex = 3
    val initValue = "string"
    val initSelectionIndex = initTargetIndex.takeIf { it <= initValue.length } ?: initValue.length
    val textFieldValueState = remember {
        mutableStateOf(TextFieldValue(
            text = initValue,
            selection = TextRange(initSelectionIndex)
        ))
    }
    TextField(
        modifier = Modifier.height(50.dp),
        value = textFieldValueState.value,
        onValueChange = { tfv -> textFieldValueState.value = tfv}
    )
}

请记住，您需要自己从onValueChange更新选择，否则用户将无法移动光标或键入/删除.

Keep in mind you need to update the selection yourself from the onValueChange otherwise the user cannot move the cursor or type/delete.

对于单行，您需要在TextField Composable上设置一个固定的高度，并且可能要清除用户输入中的'\ n'.

To the single-line, you need to set a fixed height on the TextField Composable and you probably want to sanitize '\n' from the user input.

@Composable
fun Content() {
    val initTargetIndex = 3
    val initValue = "string"
    val initSelectionIndex = initTargetIndex.takeIf { it <= initValue.length } ?: initValue.length
    val textFieldValueState = remember {
        mutableStateOf(TextFieldValue(
            text = initValue,
            selection = TextRange(initSelectionIndex)
        ))
    }
    TextField(
        modifier = Modifier.height(50.dp),
        value = textFieldValueState.value,
        onValueChange = { tfv ->
            val sanitizedText = tfv.text.replace("\n", "")
            val needUpdate = sanitizedText.length >= tfv.text.length
            if (needUpdate) {
                textFieldValueState.value = tfv
            }
        },
    
    )
}

对于后者，我对新文本进行消毒，并将其长度与状态文本进行比较，如果新文本较短，则无需更新状态，因为在消毒过程中我只是删除了字符. 如果只想阻止用户自己添加新行，则可以使高度不受限制.

For the latter, I sanitize the new text and compare the lengths of it and the state's text, if the new text is shorter I do not have to update the state because I just removed the character during sanitizing. If you just want to stop the user from adding new lines on their own, you can leave the height unconstrained.

以前的解决方案会忽略带有换行符的粘贴文本，如果要保留它，此onValueChange实现应正确处理它:

The previous solution ignores a pasted text with a line break, if you want to keep it this onValueChange implementation should handle it correctly:

val onValueChange = {tfv ->
    textFieldValueState.value.let { old ->
        val sanitizedText = tfv.text.replace("\n", "")
        val lastPositionIndex = sanitizedText.length
        val needUpdate = sanitizedText.length < tfv.text.length
        val selection = if (needUpdate) {
            tfv.selection.copy(
                start = old.selection.start.takeUnless { it > lastPositionIndex} ?: lastPositionIndex,
                end = old.selection.end.takeUnless { it > lastPositionIndex} ?: lastPositionIndex
            )
        } else tfv.selection
        val composition = old.composition?.let { oldComp ->
            if (needUpdate) {
               TextRange(
                    start = oldComp.start.takeUnless { it > lastPositionIndex} ?: lastPositionIndex,
                    end = oldComp.end.takeUnless { it > lastPositionIndex} ?: lastPositionIndex
                )
            } else oldComp
        }
        textFieldValueState.value = tfv.copy(text = sanitizedText, selection = selection, composition = composition)
    }
}

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