升级了Android Studio和Gradle之后，提示下面的警告：

WARNING: API 'variant.getJavaCompile()' is obsolete and has been replaced with 'variant.getJavaCompileProvider()'.
It will be removed at the end of 2019.
For more information, see https://d.android.com/r/tools/task-configuration-avoidance.
To determine what is calling variant.getJavaCompile(), use -Pandroid.debug.obsoleteApi=true on the command line to display a stack trace.
Affected Modules: asyncokhttp

之前gradle插件中，为了打包javadoc，需要把工程中所有的classpath都找出来，因此调用了variant.javaCompile,这是报错的原因。

image.png

如何解决

根据提示，我们只要把variant.javaCompile=>variant.javaCompileProvider就好了。

但是 variant.javaCompile.destinationDir这种换了之后会报错，因为javaCompileProvider()中没有destinationDir这个方法；
经过查证，我们我们只可以这么做：
variant.javaCompile.destinationDir => it.destinationDir

variant.javaCompile.classpath.files => it.classpath.files

替换玩之后就不会报错了：

image.png

不报警告了，但是打包javadoc的时候，提示各种类找不到

it.classpath.files是能获取到所有calsspath的，这没问题，问题出现在调用时序上，因此我们修改一下代码就好了：

task javadoc(type: Javadoc) {
    options.encoding = "utf-8"
    source = android.sourceSets.main.java.srcDirs
    classpath += files(android.bootClasspath)

    options {
        //links "http://docs.oracle.com/javase/7/docs/api/"
        linksOffline "https://developer.android.com/reference","${android.sdkDirectory}/docs/reference"
        encoding = "UTF-8"
    }
    exclude '**/BuildConfig.java'
    exclude '**/R.java'

    android.libraryVariants.all { variant ->
        variant.javaCompileProvider.configure{
            javadoc.classpath += files(it.classpath.files)
        }
    }

}

task sourcesJar(type: Jar) {
    from android.sourceSets.main.java.srcDirs
    classifier = 'sources'
}

task javadocJar(type: Jar, dependsOn: javadoc) {
    classifier = 'javadoc'
    from javadoc.destinationDir
}

artifacts {
    archives javadocJar
    archives sourcesJar
}

这是完整的可用代码：
https://github.com/andforce/release-android-lib-to-jcenter/blob/master/android-tasks.gradle