用户输入时进行验证

您可以在用户在文本字段中输入内容时（例如，输入姓名、电子邮件、地址或其他联系信息）验证输入。此验证可减少错误并节省用户时间。

版本兼容性

此实现要求您的项目 minSDK 设置为 API 级别 21 或更高。

依赖项

用户输入时进行验证

使用以下代码显示字段输入并在用户输入时验证文本。如果信息未通过验证，则错误消息将帮助用户更正输入。

class EmailViewModel : ViewModel() {
    var email by mutableStateOf("")
        private set

    val emailHasErrors by derivedStateOf {
        if (email.isNotEmpty()) {
            // Email is considered erroneous until it completely matches EMAIL_ADDRESS.
            !android.util.Patterns.EMAIL_ADDRESS.matcher(email).matches()
        } else {
            false
        }
    }

    fun updateEmail(input: String) {
        email = input
    }
}

@Composable
fun ValidatingInputTextField(
    email: String,
    updateState: (String) -> Unit,
    validatorHasErrors: Boolean
) {
    OutlinedTextField(
        modifier = Modifier
            .fillMaxWidth()
            .padding(10.dp),
        value = email,
        onValueChange = updateState,
        label = { Text("Email") },
        isError = validatorHasErrors,
        supportingText = {
            if (validatorHasErrors) {
                Text("Incorrect email format.")
            }
        }
    )
}

@Preview
@Composable
fun ValidateInput() {
    val emailViewModel: EmailViewModel = viewModel<EmailViewModel>()
    ValidatingInputTextField(
        email = emailViewModel.email,
        updateState = { input -> emailViewModel.updateEmail(input) },
        validatorHasErrors = emailViewModel.emailHasErrors
    )
}TextSnippets.kt