I want to create a string with the max number of characters allowable in the box.

setContent {
    ViewincomposetestTheme {
        var size by remember { mutableStateOf(IntSize.Zero) }
        var widthdp by remember { mutableStateOf(0.dp) }
        BoxWithConstraints(Modifier.fillMaxSize().background(Color.Yellow)) {
            val widthOfChar = 13 // how do I find this
            var string by remember {
                mutableStateOf(
                    StringBuffer()
                        .apply {
                            repeat(maxWidth.value.toInt() / widthOfChar) { append("H") }
                        }
                        .toString()
                )
            }
            Text(string)
        }
    }
}

CodePudding user response：

You can just use the maxWidth parameter of the BoxWithConstraints, then convert the obtained dp value toPx(). Decide a textsize for the TextField in sp and then do whatever calculations you want to do after converting that to Px as well. Max characters will be maxWidth / textSize, roughly.

CodePudding user response：

You can create a separate Text to calculate the size of a character, which will report you its size with onTextLayout. Using drawWithContent you can prevent it from being drawn.

Also in your example you get the width using maxWidth.value.toInt(): here you get the value of dp, not pixels. You could convert it using LocalDensity, but you also get the pixel value directly from BoxWithConstraints using constraints.maxWidth.

BoxWithConstraints(
    Modifier
        .fillMaxSize()
        .background(Color.Yellow)
) {
    var charWidth by remember { mutableStateOf<Int?>(null) }
    val string = remember(maxWidth, charWidth) {
        charWidth?.let { charWidth ->
            StringBuffer()
                .apply {
                    repeat(constraints.maxWidth / charWidth) { append("H") }
                }
                .toString()
        }
    }
    Text(
        "H",
        onTextLayout = {
            charWidth = it.size.width
        },
        modifier = Modifier.drawWithContent { }
    )
    string?.let {
        Text(string)
    }
}