如何使用CameraX VideoCapture暂停/恢复视频录制？

Android原生的MediaRecorder或Camera2 API并没有提供直接的pause()/resume()方法来暂停视频录制，常用的实现思路是分段录制多个视频文件，最后将这些片段合并成一个完整视频。以下是具体实现步骤：

核心思路 #

• 暂停录制时，调用stopRecording()结束当前片段录制并保存为临时文件
• 恢复录制时，重新初始化MediaRecorder，开始录制新的片段
• 录制完成后，将所有临时视频片段合并为一个最终视频文件

关键代码实现 #

（1）定义核心变量 #

private var mediaRecorder: MediaRecorder? = null
private var isRecording = false
private var isPaused = false
private val videoSegments = mutableListOf<File>() // 存储所有录制片段
private var currentSegmentFile: File? = null

（2）开始/恢复录制 #

fun startOrResumeRecording() {
    if (isPaused) {
        // 恢复录制：创建新临时片段文件
        currentSegmentFile = createTempVideoFile()
        initMediaRecorder(currentSegmentFile!!)
        mediaRecorder?.start()
        isPaused = false
        isRecording = true
    } else if (!isRecording) {
        // 首次启动录制
        currentSegmentFile = createTempVideoFile()
        initMediaRecorder(currentSegmentFile!!)
        mediaRecorder?.start()
        isRecording = true
    }
}

// 创建临时视频文件
private fun createTempVideoFile(): File {
    val storageDir = getExternalFilesDir(Environment.DIRECTORY_MOVIES)
    return File.createTempFile(
        "RECORD_SEGMENT_${System.currentTimeMillis()}",
        ".mp4",
        storageDir
    ).apply {
        videoSegments.add(this)
    }
}

// 初始化MediaRecorder（根据你的Camera配置调整参数）
private fun initMediaRecorder(outputFile: File) {
    mediaRecorder?.release()
    mediaRecorder = MediaRecorder().apply {
        setAudioSource(MediaRecorder.AudioSource.MIC)
        setVideoSource(MediaRecorder.VideoSource.SURFACE)
        setOutputFormat(MediaRecorder.OutputFormat.MPEG_4)
        setOutputFile(outputFile.absolutePath)
        setVideoEncoder(MediaRecorder.VideoEncoder.H264)
        setAudioEncoder(MediaRecorder.AudioEncoder.AAC)
        // 配置分辨率、帧率等参数
        setVideoSize(1280, 720)
        setVideoFrameRate(30)
        prepare()
    }
}

（3）暂停录制 #

fun pauseRecording() {
    if (isRecording && !isPaused) {
        mediaRecorder?.stop()
        mediaRecorder?.release()
        mediaRecorder = null
        isPaused = true
        isRecording = false
    }
}

（4）停止录制并合并片段 #

fun stopAndMergeRecording() {
    if (isRecording) {
        mediaRecorder?.stop()
        mediaRecorder?.release()
        mediaRecorder = null
        isRecording = false
    }

    when (videoSegments.size) {
        0 -> return
        1 -> videoSegments[0].renameTo(getFinalOutputFile())
        else -> mergeVideoSegments(videoSegments, getFinalOutputFile())
    }

    // 清理临时片段
    videoSegments.forEach { it.delete() }
    videoSegments.clear()
    isPaused = false
}

// 获取最终输出文件
private fun getFinalOutputFile(): File {
    val storageDir = getExternalFilesDir(Environment.DIRECTORY_MOVIES)
    return File(storageDir, "FINAL_RECORD_${System.currentTimeMillis()}.mp4")
}

（5）原生API实现视频合并 #

使用Android自带的MediaMuxer完成片段合并，无需第三方库：

private fun mergeVideoSegments(segments: List<File>, outputFile: File) {
    val mediaMuxer = MediaMuxer(outputFile.absolutePath, MediaMuxer.OutputFormat.MUXER_OUTPUT_MPEG_4)
    var videoTrackIndex = -1
    var audioTrackIndex = -1
    val buffer = ByteBuffer.allocate(1024 * 1024)

    segments.forEach { segment ->
        val extractor = MediaExtractor()
        extractor.setDataSource(segment.absolutePath)

        // 定位视频、音频轨道
        for (i in 0 until extractor.trackCount) {
            val format = extractor.getTrackFormat(i)
            val mime = format.getString(MediaFormat.KEY_MIME)
            when {
                mime?.startsWith("video/") == true && videoTrackIndex == -1 -> {
                    videoTrackIndex = mediaMuxer.addTrack(format)
                    extractor.selectTrack(i)
                }
                mime?.startsWith("audio/") == true && audioTrackIndex == -1 -> {
                    audioTrackIndex = mediaMuxer.addTrack(format)
                    extractor.selectTrack(i)
                }
            }
        }

        // 写入片段数据
        if (videoTrackIndex != -1 || audioTrackIndex != -1) {
            mediaMuxer.start()
            var sampleSize: Int
            while (extractor.readSampleData(buffer, 0).also { sampleSize = it } != -1) {
                val trackIndex = if (extractor.getTrackFormat(extractor.selectedTrackIndex)
                        .getString(MediaFormat.KEY_MIME)?.startsWith("video/") == true
                ) videoTrackIndex else audioTrackIndex
                
                mediaMuxer.writeSampleData(
                    trackIndex,
                    buffer,
                    MediaCodec.BufferInfo().apply {
                        offset = 0
                        size = sampleSize
                        presentationTimeUs = extractor.sampleTime
                        flags = extractor.sampleFlags
                    }
                )
                extractor.advance()
            }
        }
        extractor.release()
    }

    mediaMuxer.stop()
    mediaMuxer.release()
}

注意事项 #

• 确保申请必要权限：RECORD_AUDIO、CAMERA，Android 10+无需WRITE_EXTERNAL_STORAGE，使用Scoped Storage即可
• 临时文件需及时清理，避免占用冗余存储空间
• 合并视频时需保证音视频同步，可通过调整presentationTimeUs参数优化过渡效果
• 若使用Camera2 API，需适配MediaRecorder的Surface配置，配合Camera2的预览流程

内容的提问来源于stack exchange，提问作者khushhal goyal