警告：警告：注释处理器 'android.arch.lifecycle.LifecycleProcessor' 支持的源版本 'RELEASE_7' 小于 -source '1.8'

Question

尝试使用 Android Studio 3 Canary 5 with Architecture Components 和 Kotlin 构建示例时给出此警告。

谁能告诉我原因？

谢谢，欧维

编辑 #1：这是 Dan Lew

前段时间制作的示例

https://github.com/dlew/android-architecture-counter-sample

build.gradle:

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

android {
    compileSdkVersion 25
    buildToolsVersion rootProject.ext.buildToolsVersion
    defaultConfig {
        applicationId "net.danlew.counter"
        minSdkVersion 23
        targetSdkVersion 25
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile "com.android.support:appcompat-v7:${rootProject.ext.supportLibVersion}"
    compile "com.android.support:recyclerview-v7:${rootProject.ext.supportLibVersion}"
    compile "com.android.support:design:${rootProject.ext.supportLibVersion}"
    compile "com.android.support:cardview-v7:${rootProject.ext.supportLibVersion}"
    compile 'com.android.support.constraint:constraint-layout:1.0.2'
    testCompile 'junit:junit:4.12'

    compile "android.arch.lifecycle:extensions:${rootProject.archLifecycleVersion}"
    compile "android.arch.persistence.room:runtime:${rootProject.archRoomVersion}"
    compile "android.arch.persistence.room:rxjava2:${rootProject.archRoomVersion}"
    kapt "android.arch.lifecycle:compiler:${rootProject.archLifecycleVersion}"
    kapt "android.arch.persistence.room:compiler:${rootProject.archRoomVersion}"
    compile "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"

    String butterKnifeVersion = '8.5.1'
    compile "com.jakewharton:butterknife:$butterKnifeVersion"
    kapt "com.jakewharton:butterknife-compiler:$butterKnifeVersion"

    compile 'io.reactivex.rxjava2:rxjava:2.1.0'

    String daggerVersion = '2.10'
    compile "com.google.dagger:dagger:$daggerVersion"
    kapt "com.google.dagger:dagger-compiler:$daggerVersion"

    String rxBindingVersion = '2.0.0'
    compile "com.jakewharton.rxbinding2:rxbinding:$rxBindingVersion"
    compile "com.jakewharton.rxbinding2:rxbinding-kotlin:$rxBindingVersion"

    compile 'com.jakewharton.timber:timber:4.5.1'

    compile 'com.jakewharton.rxrelay2:rxrelay:2.0.0'
}

repositories {
    mavenCentral()
}

Answer 1

只是添加这个答案以供将来参考：不久前 Android Arch Components 团队也提出了同样的问题，official answer 目前是：

(...) it is just a warning. Should not be a problem.

这适用于遵循问题标题中提到的格式的警告，包括：

w: warning: Supported source version 'RELEASE_7' from annotation processor 'android.arch.lifecycle.LifecycleProcessor' less than -source '1.8' w:

w: warning: Supported source version 'RELEASE_7' from annotation processor 'android.arch.persistence.room.RoomProcessor' less than -source '1.8' w:

基本上是 javac 通知您这些注解处理器是针对与模块源代码级别不同的（旧）版本 Java (Java 7) 编译并生成代码的设置为 (Java 8)。这样做的原因是编译器无法保证处理器仍然会正确运行[但开发人员可以并且在这种特殊情况下已经做到了]。

请注意，如果您删除 -Xlint 编译器标志，仍会发出警告，但不幸的是，由于没有使用 -nowarn，它无法被抑制。

Answer 2

有一个 Java 8 注释处理器现在 arch 组件是稳定的所以替换：

"android.arch.lifecycle:compiler:${rootProject.archLifecycleVersion}"

和

"android.arch.lifecycle:common-java8:1.0.0"

警告：警告：注释处理器 'android.arch.lifecycle.LifecycleProcessor' 支持的源版本 'RELEASE_7' 小于 -source '1.8'

Warning: warning: Supported source version 'RELEASE_7' from annotation processor 'android.arch.lifecycle.LifecycleProcessor' less than -source '1.8'

android

kotlin

android-studio

android-architecture-components