Kotlin函数类型代替函数接口lambda

您可以使用属性来保存处理程序。

class ResultReceiverTest(handler : Handler) : ResultReceiver(handler) {
    private var resultHandler: ((resultCode : Int, resultData: Bundle) -> Unit)? = null

    fun onResult(result : (resultCode : Int, resultData: Bundle) -> Unit){
        resultHandler = result
    }

    override fun onReceiveResult(resultCode: Int, resultData: Bundle){
        resultHandler?.invoke(resultCode, resultData)
    }
}

为什么不这样做呢?在初始化期间提供on-result回调:

class ResultReceiverTest(handler: Handler, private val onResult: (Int, Bundle) -> Unit) : ResultReceiver(handler) {
  override fun onReceiveResult(resultCode: Int, resultData: Bundle) {
    onResult(resultCode, resultData)
  }
}

// Do it with a function reference
class StartService {

  private var resultReceiverTest = ResultReceiverTest(Handler(), this::doSomethingWithResult)

  fun doSomethingWithResult(resultCode: Int, resultData: Bundle) {
    println(resultCode)
  }
}

// OR DO IT INLINE
class StartService {

  private var resultReceiverTest = ResultReceiverTest(Handler()) { resultCode, resultData -> println(resultCode) }

}