异常特征：

编译时候报错，如下：

* What went wrong:
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.

原因分析：

编译时缺少了一些配置参数。

解决方案：

 在app的build.gradle文件的defaultConfig加入javaCompileOptions配置，即可

 defaultConfig {
        applicationId "com.atguigu.shoppingmall"
        minSdkVersion 14
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        //加入javaCompileOptions配置
        javaCompileOptions {
            annotationProcessorOptions {
                includeCompileClasspath = true
            }
        }

        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
            }
        }
    }