android-kotlin 错误 : unresolved reference databinding & ActivityMainBinding

Question

我使用的是 Android Studio 3.0 Canary 6 版本。我在我的类中启用了数据绑定(bind)，代码没有显示任何错误。但是，当我构建 APK 时，构建失败并显示以下错误:

Error:(8, 37) Unresolved reference: databinding  
Error:(22, 26) Unresolved reference: ActivityMainBinding  
Error:(38, 50) Unresolved reference: ActivityMainBinding  
Error:(43, 52) Unresolved reference: ActivityMainBinding  
Error:(46, 52) Unresolved reference: ActivityMainBinding  
Error:(49, 52) Unresolved reference: ActivityMainBinding  
Error:(52, 52) Unresolved reference: ActivityMainBinding  
Error:(55, 52) Unresolved reference: ActivityMainBinding  
Error:(58, 52) Unresolved reference: ActivityMainBinding  
Error:(61, 52) Unresolved reference: ActivityMainBinding  
Error:(64, 52) Unresolved reference: ActivityMainBinding  
Error:(67, 52) Unresolved reference: ActivityMainBinding  
Error:(70, 52) Unresolved reference: ActivityMainBinding  
Error:(73, 52) Unresolved reference: ActivityMainBinding  
Error:Execution failed for task ':app:compileDebugKotlin'.  
Compilation error. See log for more details

顶层build.gradle文件如下:

buildscript {
ext.kotlin_version = '1.1.3-2'
repositories {
    google()
    jcenter()
}
dependencies {
    classpath 'com.android.tools.build:gradle:3.0.0-alpha6'
    classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"

    // NOTE: Do not place your application dependencies here; they belong
    // in the individual module build.gradle files
}
}

allprojects {
    repositories {
        google()
        jcenter()
        mavenCentral()
    }
}

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

模块build.gradle文件如下:

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

apply plugin: 'kotlin-kapt'

android {
    compileSdkVersion 26
    buildToolsVersion "26.0.1"
    defaultConfig {
        applicationId "com.example.jimil.calculator"
        minSdkVersion 15
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner 
            "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled true
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 
                'proguard-rules.pro'
        }
    }
    dataBinding{
        enabled =  true
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    androidTestImplementation ('com.android.support.test.espresso:espresso-
        core:3.0.1', {
            exclude group: 'com.android.support', module: 'support-
                annotations'
    })
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:26.1.0'
    testImplementation 'junit:junit:4.12'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    kapt 'com.android.databinding:compiler:3.0.0-alpha6'
}

kapt {
    generateStubs = true
}

MainActivity.kt 类是:

import com.example.jimil.calculator.databinding.ActivityMainBinding  
...  
class MainActivity : AppCompatActivity() {  
    private var binding: ActivityMainBinding? = null  
    ...  
}

请帮我解决构建错误。

Answer 1

你的 gradle 中有几个错误。

当前的 Gradle-Version 是 3.0.0-beta 3。这意味着您需要将类路径更改为

classpath 'com.android.tools.build:gradle:3.0.0-beta6'

同样适用于您的依赖项

kapt "com.android.databinding:compiler:3.0.0-beta6"

您还应该在适当的文件夹中提供您的插件。

apply plugin: 'com.android.application'
apply plugin: 'kotlin-android'
apply plugin: 'kotlin-kapt'
apply plugin: 'kotlin-android-extensions'

您还应该启用编译选项，让您的注解处理器使用 Java8 依赖项(这可能是 Kotlin 目标 1.8 所必需的)。

compileOptions {
    sourceCompatibility JavaVersion.VERSION_1_8
    targetCompatibility JavaVersion.VERSION_1_8
}

完成后使缓存失效并重新启动。

如果错误仍然存​​在，请检查 Gradle 控制台。您的 XML 文件中可能存在错误，这会阻止您的注释处理器生成数据绑定(bind)类。