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与Architecture Components和Kotlin构建示例时会发出此警告.

谁能告诉我原因？

谢谢,Ove

编辑#1:这是Dan Lew不久前制作的一个样本

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

的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

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}"

同

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

Answer 2

只需添加此答案以备将来参考:不久前Android Arch Components团队也提出了同样的问题,现在的官方答案是:

(...)这只是一个警告.应该不是问题.

这适用于遵循问题标题中提到的格式的警告,包括:

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

w:警告:注释处理器'android.arch.persistence.room.RoomProcessor'支持的源版本'RELEASE_7'小于-source'1.8'w:

基本上,它javac告诉您这些注释处理器是针对不同(较旧)版本的Java(Java 7)编译而生成的,而不是模块的源级别设置为(Java 8).这样做的原因是编译器不能做任何承诺,处理器仍然会正常行为[但开发人员可以在这种特殊情况下做到].

请注意,如果删除-Xlint编译器标志,仍会发出警告,因此-nowarn不能轻易地禁止使用它.