如何通过Kotlin中的参数除外的方法？

Question

我希望通过一种实现mediarecorder.oninfolistener的方法。

目前，我使用代码A传递实现Mediarecorder.oninfolistener的方法。

还有其他方法吗？也许就像代码B一样。

代码a

class HomeViewModel(...) : AndroidViewModel(mApplication) {

    fun startRecord() {
        startRecord(savedfilename){
             mr, what, extra ->
                 if (what == MediaRecorder.MEDIA_RECORDER_INFO_MAX_DURATION_REACHED) {
                     stopRecord()
                 }            
        }

    }

}


class RecordService : Service() {  

    fun startRecord(filename:String, mOnInfoListener: MediaRecorder.OnInfoListener){
       mRecorder = MediaRecorder()
        mRecorder?.let {    
            with(it) {                  
                setOnInfoListener(mOnInfoListener)    
            }
        }
    }    
}

代码b

class HomeViewModel(...) : AndroidViewModel(mApplication) {

{
    //I save  mOnInfoListener to memory ?   
    val mOnInfoListener = object: MediaRecorder.OnInfoListener{
        mr, what, extra ->
           if (what == MediaRecorder.MEDIA_RECORDER_INFO_MAX_DURATION_REACHED) {
              stopRecord()
          }
    }

    fun startRecord() {
        startRecord(savedfilename)    
    }

}


class RecordService : Service() {  

    fun startRecord(filename:String){
       mRecorder = MediaRecorder()
        mRecorder?.let {    
            with(it) {
                setOnInfoListener(mOnInfoListener)  //  I get mOnInfoListener from memory ?    
            }
        }
    }    
}

Answer 1

代码A在将lambda作为参数传递方面看起来不错。但是我会做出一些改进。

I would encapsulate the work with MediaRecorder in one class, eg RecordService, HomeViewModel doesn't need to know anything about what tools RecordService用于制作记录。而且，如果您需要在录音机的事件上做出反应，则可以为此创建一个其他接口。带有所有接口和事件的示例代码看起来如下：

sealed interface Event
object MaxDurationReachedEvent : Event
//... create another events if need

interface RecordServiceEventListener {
    fun onRecordEvent(event: Event)
}

interface RecordService {
    fun startRecord(filename: String)
    fun registerEventListener(listener: RecordServiceEventListener)
    fun unregisterEventListener(listener: RecordServiceEventListener)

}

class RecordServiceImpl : Service(), RecordService {

    private var recorder: MediaRecorder? = null
    private var eventListeners: MutableList<RecordServiceEventListener> = mutableListOf()

    override fun startRecord(filename: String) {
        recorder = MediaRecorder()
        recorder?.setOnInfoListener { mr, what, extra ->
            if (what == MediaRecorder.MEDIA_RECORDER_INFO_MAX_DURATION_REACHED) {
                eventListeners.forEach { it.onRecordEvent(MaxDurationReachedEvent) }
            }
        }
    }

    override fun registerEventListener(listener: RecordServiceEventListener) {
        eventListeners.add(listener)
    }

    override fun unregisterEventListener(listener: RecordServiceEventListener) {
        eventListeners.remove(listener)
    }
}

class HomeViewModel(private val recordService: RecordService) : ViewModel(), RecordServiceEventListener {

    init {
        recordService.registerEventListener(this)
    }

    override fun onCleared() {
        recordService.unregisterEventListener(this)
    }

    fun startRecord() {
        recordService.startRecord(savedFilename)
    }

    override fun onRecordEvent(event: Event) {
        when (event) {
            MaxDurationReachedEvent -> { ... /* Do something */ }
        }
    }
}

最好使用接口而不是混凝土实现。另外，我不建议在命名变量时使用m前缀，它是 java 语言的样式，而不是 kotlin 。

PS Flow可用于发射录音机的事件，而不是RecordserviceEventListener，但这是另一个故事:)

Answer 2

干得好：

class HomeViewModel(...) : AndroidViewModel(mApplication) {
    //I save  mOnInfoListener to memory ?
    val mOnInfoListener = object : MediaRecorder.OnInfoListener {
        override fun onInfo(mr: MediaRecorder, what: Int, extra: Int) {
            if (what == MediaRecorder.MEDIA_RECORDER_INFO_MAX_DURATION_REACHED) {
                stopRecord()
            }
        }
    }


    fun startRecord() {
        startRecord(savedfilename)
    }

}


class RecordService(private val mOnInfoListener: MediaRecorder.OnInfoListener) : Service() {

    fun startRecord(filename: String) {
        val mRecorder = MediaRecorder()
        mRecorder.setOnInfoListener(mOnInfoListener)  //  I get mOnInfoListener from memory ?
    }
}