我們大多使用 android studio 改變生成安裝包命名會用以下方式：

applicationVariants.all { variant ->

    variant.outputs.each { out ->

        def oFile =out.outputFile  // outputFile causes failure

        //...
    }
}

　　但是更新到as3.0以後，會同步失敗。stackoverflow上有人（http://stackoverflow.com/questions/44044031/grade-plugin-3-alpha1-outputfile-causes-error）說：

This build error occurs because variant-specific tasks are no longer created during the configuration stage.
This results in the plugin not knowing all of its outputs up front, but it also means faster configuration times.
As an alternative, we will introduce new APIs to provide similar functionality.

查詢官網介紹：https://developer.android.com/studio/preview/features/new-android-plugin-migration.html#variant_api

API change in variant output 

發現解決方案：

// If you use each() to iterate through the variant objects,
// you need to start using all(). That‘s because each() iterates
// through only the objects that already exist during configuration time—
// but those object don‘t exist at configuration time with the new model.
// However, all() adapts to the new model by picking up object as they are
// added during execution.
android.applicationVariants.all { variant ->
    variant.outputs.all {
        outputFileName = "${variant.name}-${variant.versionName}.apk"
    }
}

Android studio 3.0 引起的 outputFile sync failed：not vaild