如何在Android Kotlin中封装自定义MediaRecorder？

Question

我是Kotlin编程的新手。我使用以下代码将音频录制为 AudioRecorderDialogFragment的一部分：

fun startVoiceRecorder(voiceFilename: String) {

    if (mAudioRecorder == null) {
        // We don't have an AudioRecorder, so we build one
        mAudioRecorder = MediaRecorder()
        mAudioRecorder?.setAudioSource(MediaRecorder.AudioSource.MIC)
        mAudioRecorder?.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
        mAudioRecorder?.setAudioEncoder(MediaRecorder.OutputFormat.MPEG_4)
        val audioOutputFile = Environment.getExternalStorageDirectory().absolutePath + "/" + Environment.DIRECTORY_DOWNLOADS + "/" + voiceFilename
        mAudioRecorder?.setOutputFile(audioOutputFile)
    }

    // We do have an AudioRecorder
    if (!isRecording!!) {
        // We try to record
        try {
            mAudioRecorder?.prepare()
            mAudioRecorder?.start()
            isRecording = true
        } catch (e: IllegalStateException) {
            e.printStackTrace()
        } catch (e: IOException) {
            e.printStackTrace()
        }

    } else { // We seem to be recording already
        isRecording = false
        if (null != mAudioRecorder) {
            try {
                mAudioRecorder?.stop()
            } catch (ex: RuntimeException) {
                // Ignore
            }
        }
        mAudioRecorder?.reset()
        mAudioRecorder?.release()
        mAudioRecorder = null
    }
}

fun stopVoiceRecorder() {
    isRecording = false
    if (null != mAudioRecorder) {
        try {
            mAudioRecorder?.stop()
        } catch (ex: RuntimeException) {
            // Ignore
        }
    }
    mAudioRecorder?.reset()
    mAudioRecorder?.release()
    mAudioRecorder = null
    Toast.makeText(context, "Audio recorded successfully", Toast.LENGTH_LONG).show()
}

这完美无瑕。但是，我想将此代码封装在AudioRecorder class中。我到底该怎么做？