当我在 android studio 中添加导航时，出现 "Build gradle start up" 错误和 "unable to resolve class val :13" 错误

Question

我正在学习 Kotlin 语言，当我想添加导航时，我按照官方网站建议的步骤进行操作，但我的项目不起作用

我遇到的错误Gradle同步失败：原因：启动失败：构建文件 'C:\Users....\Desktop\AndroidStudioProjeler\NavigationKotlin\build.gradle': 13: 无法解析 class val @ 第 13 行，第 13 列。 val nav_version = "2.3.5" ^ 1 个错误

第 13 行 =val nav_version = "2.3.5"

    plugins {
    id 'com.android.application'
    id 'kotlin-android'
    id("androidx.navigation.safeargs")
    id("androidx.navigation.safeargs.kotlin")
}

android {
    compileSdk 31

    defaultConfig {
        applicationId "com.example.navigationkotlin"
        minSdk 23
        targetSdk 31
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
    kotlinOptions {
        jvmTarget = '1.8'
    }
}

dependencies {

        val nav_version = "2.3.5"


    // Kotlin
    implementation("androidx.navigation:navigation-fragment-ktx:$nav_version")
    implementation("androidx.navigation:navigation-ui-ktx:$nav_version")


    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.4.0'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.2'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
  

}

buil.gradle


buildscript {
  ext.nav_version = "2.3.5"
  repositories {
      google()
      mavenCentral()
  }
  dependencies {
      classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
      classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:2.3.5"

      val nav_version = "2.3.5"
      classpath("androidx.navigation:navigation-safe-args-gradle-plugin:$nav_version")
  }
}

task clean(type: Delete) {
  delete rootProject.buildDir
}

Answer 1

在项目中 gradle:

buildscript {
    ext.kotlinVersion = '1.4.30'
    ext.navigationVersion = "2.3.5"
    repositories {
        //...
    }

    dependencies {
        //...
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlinVersion"
        classpath "androidx.navigation:navigation-safe-args-gradle-plugin:$navigationVersion"
        //...
    }
}

Answer 2

首先，我开始了一个新项目，然后我没有用“val”来定义它，而是用“def”来定义它，所以=def nav_version = “2.3.0”。我使用 2.3.0 而不是 2.3.5 并删除了“实现”括号。

Answer 3

就拿一个低版本(比如->2.3.0)把val改成def

像一个：def nav_version = "2.3.0"

当我在 android studio 中添加导航时，出现 "Build gradle start up" 错误和 "unable to resolve class val :13" 错误

When I add navigation in android studio, I get "Build gradle start up" error and "unable to resolve class val :13" errors

navigation

android

kotlin