解決錯誤Annotation processors must be explicitly declared now

一、錯誤信息

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.

二、解決方案

在APP的build.gradle中

android {
    ...
    defaultConfig {
        ...
        //添加如下配置就OK了

    javaCompileOptions { annotationProcessorOptions { includeCompileClasspath = true } }

    }
    ...
}