app的gradle 配置如下

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'
...
dependencies {
     ...
     implementation"org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
     ...
}

项目的gradle配置如下

buildscript {
    ext.kotlin_version = '1.2.30'
    ...
    dependencies {
        classpath 'com.android.tools.build:gradle:3.1.3'
        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
}

activity 代码

class MainActivity : MyActivity() {

    private var mBinding: AppActivityMainBinding? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        init()
    }

    private fun init() {
        mBinding = DataBindingUtil.setContentView(this, R.layout.app_activity_main)
    }
}

本来今天开开心心，然后编译报红：
:unresolved reference databinding

修改：
在app的gradle里添加

apply plugin: 'kotlin-kapt'
dependencies {
    ...
    kapt "com.android.databinding:compiler:3.1.3"
}

参考文献：
https://stackoverflow.com/questions/33165324/kotlin-android-unresolved-reference-databinding

/

• 更新 最近笔者把升级到了AndroidStudio3.2版本，以上方式报错

AndroidStudio下kotlin + dataBinding 编译报红
错误: 找不到符号 @Nullable DataBindingComponent component)
笔者错误原因，gradle 配置问题，错误的Gradle如下

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

apply plugin: 'kotlin-kapt'

android {
  ······

   dataBinding {
       enabled true
   }
}
dependencies {
   kapt "com.android.databinding:compiler:3.1.4"
   implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 ......
}

解决方式
删除 kapt "com.android.databinding:compiler:3.1.4"