Android 3.0找不到butterknife-7.0.1.jar

错误日志：

Error:Execution failed for task ':app:javaPreCompileDebug'.
> Annotation processors must be explicitly declared now.  The following dependencies on the compile classpath are found to contain annotation processor.  Please add them to the annotationProcessor configuration.
    - butterknife-7.0.1.jar (com.jakewharton:butterknife:7.0.1)
  Alternatively, set android.defaultConfig.javaCompileOptions.annotationProcessorOptions.includeCompileClasspath = true to continue with previous behavior.  Note that this option is deprecated and will be removed in the future.
  See https://developer.android.com/r/tools/annotation-processor-error-message.html for more details.

解决办法：

在主项目的build.gradle添加下面语句：

javaCompileOptions {
    annotationProcessorOptions {
        includeCompileClasspath = true
    }
}