参考：
Android Butterknife 8.4.0 使用方法总结
butterKnife注解不起作用问题

如何添加依赖

1.在项目的project 的build.gredle 文件中的dependencies标签下添加,classpath ‘com.neenbedankt.gradle.plugins:android-apt:1.8’，如下：

buildscript {
    repositories {
        jcenter()
    }

    dependencies {
        classpath 'com.android.tools.build:gradle:2.2.2'
        classpath 'com.neenbedankt.gradle.plugins:android-apt:1.8'
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}

2.在module的build.gredle 文件中添加

apply plugin: 'android-apt'

3.在module的build.gredle 文件中的dependencies标签中添加

compile 'com.jakewharton:butterknife:8.4.0'
apt 'com.jakewharton:butterknife-compiler:8.4.0'

完整演示：

apply plugin: 'com.android.application'
apply plugin: 'android-apt'

android {
    compileSdkVersion 24
    buildToolsVersion "24.0.3"

    defaultConfig {
        applicationId "com.zyj.wifi"
        minSdkVersion 14
        targetSdkVersion 24
        versionCode 1
        versionName "1.0"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    
    compile 'com.jakewharton:butterknife:8.4.0'
    apt 'com.jakewharton:butterknife-compiler:8.4.0'
}