我创建了一个应用程序我正在做一个视频采集活动，我想捕捉preVIEW框架，以及一个播放按钮来使用。我给自己定了 SurfaceView 在的onCreate（...）并迷上了相机的preVIEW显示在 SurfaceHolder.Callback ：

I'm creating a video capture activity for an app I'm making, and I want to capture a preview frame as well to use as a playback button. I've set the SurfaceView up in onCreate(...) and hooked up the camera's preview display in the SurfaceHolder.Callback:

private Callback mSurfaceViewCallback = new Callback() {

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
        mSurfaceCreated = false;
    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {
        try {
            mSurfaceCreated = true;
            mCamera.setPreviewDisplay(mHolder);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,
            int height) {
        try {
            mSurfaceCreated = true;
            mCamera.setPreviewDisplay(mHolder);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
};

这对于静态相机应用工作的罚款。相机preVIEW开启和关闭的onPause（）和 onResume（）：

@Override
protected void onResume() {
    super.onResume();
    if(mCamera!=null)
        mCamera.startPreview();
}

@Override
protected void onPause() {
    if(mCamera!=null)
        mCamera.stopPreview();
    super.onPause();
}

和我已经设置了 MediaRecorder 像这样的：

and I've set the MediaRecorder up like this:

protected void startRecording() {
    mMediaRecorder = new MediaRecorder();
    mCamera.unlock();
    mMediaRecorder.setCamera(mCamera);
    mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
    mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
    mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_LOW));

    mMediaRecorder.setMaxDuration(10000);
    mMediaRecorder.setOutputFile(new File(getFilesDir(), mChallengeUUID + ".mp4").getAbsolutePath());
    mMediaRecorder.setPreviewDisplay(mHolder.getSurface());
    try {
        mMediaRecorder.prepare();
    } catch (IllegalStateException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    mCamera.setOneShotPreviewCallback(mPreviewCallback);
    mMediaRecorder.start();
}

这是倒数第二行，但是，不工作。我的相机。previewCallback 的在previewFrame（...）方法被错过。

That penultimate line, however, isn't working. My Camera.PreviewCallback's onPreviewFrame(...) method is being missed.

有它的目的是，正如我所说，以获得当正在录像，显示给用户的起始帧。为什么没有回调被打？

The purpose of having it is, as I say, to get a frame from the beginning of when the video is being recorded to display to the user. Why isn't the callback being hit?

推荐答案

mCamera.unlock（）从分离过程中的相机。因此有必要呼吁：

mCamera.unlock() detaches the camera from the process. It's necessary to call:

mCamera.reconnect();

在调用之前：

before calling:

mCamera.setOneShotPreviewCallback(mPreviewCallback);

（但一切后）。

(but after everything else).