将 TextFieldValue 转换为 Double（Kotlin、Jetpack Compose）

Question

那里！

我正在使用 Jetpack Compose 编写 BMI 计算器。 我设置了两个“TextFieldValue”函数来输入用户的身高和体重。这两个函数都返回“文本”，我无法将其转换为 Double 类型，因此我可以进行数学运算！

我坚持了3个多小时！ 我开始从事 Android 开发，因此非常感谢您的帮助！ 嗯，非常感谢！

我试过：

// Insert function:

fun insertWeight (): TextFieldValue {
    var text by remember {
        mutableStateOf(TextFieldValue(""))
    }
    TextField(
        value = text,
        onValueChange = {
            text = it
        },
        label = {
            Text (text = "Weight")
        },
        placeholder = {
            Text (text = "Insert your weight in Kilograms")
        },
        keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Number)
    )
    return text
}

然后（在 MainActivity 中）

// I couldn't find out how to do it directly without passing by String (I even don't know if it is right"
val weight: Double = insertWeight().toString().toDouble()

我也试过另一种东西，将函数类型从“TextFieldValue”更改为“Double”，然后将函数中的返回更改为“return text.toString().toDouble()”，然后我意识到这是一个非常愚蠢的尝试 hahahaha 如果类型不匹配，compose 函数将致命地终止应用程序！

Answer 1

你不能在普通函数中使用

composable function

或者不能返回数据（因为可组合函数不是普通函数，它是一个小部件或Ui），你可以通过下面的代码实现上面的事情。希望对你有帮助。

@Composable
fun TextFieldValueScreen() {

    var weight by remember { mutableStateOf("") }
    var height by remember { mutableStateOf("") }
    var total by remember { mutableStateOf(0.0) }
    val context = LocalContext.current

    Column(
        modifier = Modifier
            .fillMaxWidth()
            .padding(20.dp),
        horizontalAlignment = Alignment.CenterHorizontally
    ) {
        CommonTextField(
            title = "Weight",
            placeholder = "Insert your weight in Kilograms",
            text = weight,
            onValueChange = { weight = it }
        )
        Spacer(modifier = Modifier.height(20.dp))
        CommonTextField(
            title = "Height",
            placeholder = "Insert your height in meter",
            text = height,
            onValueChange = { height = it }
        )
        Spacer(modifier = Modifier.height(20.dp))
        Button(onClick = {
            if (height.isNotEmpty() && weight.isNotEmpty()) {
                total = (weight.toDouble()) / (height.toDouble() * height.toDouble())
            } else {
                Toast.makeText(context, "Please type height and weight", Toast.LENGTH_SHORT).show()
            }
        }) {
            Text(text = "Calculate")
        }
        Spacer(modifier = Modifier.height(20.dp))
        if (total != 0.0)
            Text(
                text = "BMI is ${String.format(Locale.US, "%.2f", total)}",
                style = TextStyle(
                    fontSize = 25.sp,
                    fontWeight = FontWeight.SemiBold,
                    fontStyle = FontStyle.Italic,
                )
            )
    }

}

@Composable
fun CommonTextField(
    title: String,
    placeholder: String,
    text: String,
    onValueChange: (String) -> Unit
) {

    TextField(
        value = text,
        onValueChange = onValueChange,
        label = {
            Text(text = title)
        },
        placeholder = {
            Text(text = placeholder)
        },
        keyboardOptions = KeyboardOptions(keyboardType = KeyboardType.Phone)
    )

}

输出