Android Studio中小费计算器使用toDouble()遇未解析引用错误求助

我在Android Studio开发Android Basics Kotlin课程的小费计算器应用时，尝试用toDouble()将字符串转为Double类型，出现「unresolved reference: toDouble」错误，即使粘贴课程官网示例代码问题依然存在，调用toInt()也遇到相同报错。

相关代码 #

MainActivity.kt

package com.example.tiptime

import java.text.NumberFormat
import androidx.appcompat.app.AppCompatActivity
import android.os.Bundle
import com.example.tiptime.databinding.ActivityMainBinding

class MainActivity : AppCompatActivity() {

    lateinit var binding: ActivityMainBinding

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        binding = ActivityMainBinding.inflate(layoutInflater)
        setContentView(binding.root)
        binding.calculateButton.setOnClickListener{ calculateTip() }
    }

    fun calculateTip() {
        val stringInTextField = binding.costOfService.text.toString()
        val cost = stringInTextField.toDouble()
    }
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:padding="16dp"
    tools:context=".MainActivity"
    tools:ignore="UseSwitchCompatOrMaterialXml">

    <EditText
        android:id="@+id/cost_of_service"
        android:layout_width="160dp"
        android:layout_height="wrap_content"
        android:hint="@string/cost_of_service"
        android:inputType="numberDecimal"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        android:autofillHints="@string/cost_of_service" />

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/how_was_the_service"
        android:id="@+id/service_question"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/cost_of_service"/>

    <RadioGroup
        android:layout_height="wrap_content"
        android:layout_width="wrap_content"
        android:id="@+id/tip_options"
        android:checkedButton="@+id/option_twenty_percent"
        app:layout_constraintTop_toBottomOf="@id/service_question"
        app:layout_constraintStart_toStartOf="parent">

        <RadioButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/option_twenty_percent"
            android:text="@string/amazing_20"/>

        <RadioButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/option_eighteen_percent"
            android:text="@string/great_18"/>

        <RadioButton
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:id="@+id/option_fifteen_percent"
            android:text="@string/ok_15"/>
    </RadioGroup>

    <Switch
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:id="@+id/round_up_switch"
        android:text="@string/round_up_tip"
        android:checked="true"

        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@id/tip_options" />
    <Button
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:text="@string/calculate"
        android:id="@+id/calculate_button"

        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@id/round_up_switch"
        />
    <TextView
        android:id="@+id/tip_result"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/tip_amount"

        app:layout_constraintTop_toBottomOf="@id/calculate_button"
        app:layout_constraintEnd_toEndOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

错误截图 #

解决方案 #

• 检查Kotlin依赖配置
  确保项目根目录build.gradle（Project级）中Kotlin插件版本为稳定版：

  plugins {
      id 'com.android.application' version '7.4.2' apply false
      id 'com.android.library' version '7.4.2' apply false
      id 'org.jetbrains.kotlin.android' version '1.8.20' apply false
  }
  

  并在Module级build.gradle中启用Kotlin插件：

  plugins {
      id 'com.android.application'
      id 'org.jetbrains.kotlin.android'
  }
  

• 清理重建项目并清除缓存
  依次执行：

  1. 菜单栏Build > Clean Project
  2. Build > Rebuild Project
  3. File > Invalidate Caches...，选择「Invalidate and Restart」重启IDE

• 确认视图绑定启用
  在Module级build.gradle中确保开启视图绑定：

  android {
      ...
      buildFeatures {
          viewBinding true
      }
  }
  

• 添加空字符串校验（可选）
  提前处理空输入，避免后续潜在异常：

  fun calculateTip() {
      val stringInTextField = binding.costOfService.text.toString()
      if (stringInTextField.isNotBlank()) {
          val cost = stringInTextField.toDouble()
          // 后续小费计算逻辑
      }
  }
  

内容的提问来源于stack exchange，提问作者VakhtangChachanidze