導入項目時，發現之前項目的butter knife報錯，用到註解的應該都會報錯
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
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.

在app的build中
android {
...
defaultConfig {
...
//添加如下配置就OK了
javaCompileOptions { annotationProcessorOptions { includeCompileClasspath = true } }
}
...
}

Android Studio錯誤日誌-註解報錯Annotation processors must be explicitly declared now.