Media Recorder在Android摄像头启动失败

我在我的表面上进行了视频预览,但是当我按下开始按钮时,它会出现错误“MEDIA.RECORDER.START(Native MEthod)”.
这是我的代码请帮帮我们.

@Override
    public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
            surfaceView = (SurfaceView) findViewById(R.id.surface_camera);
            surfaceHolder = surfaceView.getHolder();
            surfaceHolder.addCallback(this);
            surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
            Button start =(Button)findViewById(R.id.start);
            Button stop =(Button)findViewById(R.id.stop);
            stop.setonClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // Todo Auto-generated method stub
                    camera.stopPreview();
                    stopRecording();
                }
            });
            start.setonClickListener(new OnClickListener() {

                @Override
                public void onClick(View v) {
                    // Todo Auto-generated method stub
                    startRecording();
                }
            });
    }

    @Override
public void surfaceCreated(SurfaceHolder holder) {
    camera = Camera.open();
    if (camera != null){
        Camera.Parameters params = camera.getParameters();
        camera.setParameters(params);
    }
    else {
        Toast.makeText(getApplicationContext(),"Camera not available!",Toast.LENGTH_LONG).show();
        finish();
    }
}

@Override
public void surfaceChanged(SurfaceHolder holder,int format,int width,int height) {
    if (previewRunning){
        camera.stopPreview();
    }
    Camera.Parameters p = camera.getParameters();
     List<Camera.Size> sizes = p.getSupportedPreviewSizes(); 
     Camera.Size cs = sizes.get(0);  
     p.setPreviewSize(cs.width,cs.height);  
       camera.setParameters(p);

    try {
        camera.setPreviewdisplay(holder);
        camera.startPreview();
        previewRunning = true;
    }
    catch (IOException e) {
        Log.e(TAG,e.getMessage());
        e.printstacktrace();
    }
}

 private MediaRecorder mediaRecorder;
    private final int maxDurationInMs = 20000;
    private final long maxFileSizeInBytes = 500000;
    private final int videoFramesPerSecond = 20;

    public boolean startRecording(){
        try {
            camera.unlock();

            mediaRecorder = new MediaRecorder();

            mediaRecorder.setCamera(camera);
            mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
            mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);

            mediaRecorder.setoutputFormat(MediaRecorder.OutputFormat.DEFAULT);

            mediaRecorder.setMaxDuration(maxDurationInMs);

        File tempFile = new File(getCacheDir(),"test.mp4");
            mediaRecorder.setoutputFile(tempFile.getPath());

            mediaRecorder.setVideoFrameRate(videoFramesPerSecond);
            mediaRecorder.setVideoSize(surfaceView.getWidth(),surfaceView.getHeight());

            mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT);
            mediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.DEFAULT);

            mediaRecorder.setPreviewdisplay(surfaceHolder.getSurface());

            mediaRecorder.setMaxFileSize(maxFileSizeInBytes);

                        mediaRecorder.prepare();
            mediaRecorder.start();

            return true;
        } catch (IllegalStateException e) {
            Log.e(TAG,e.getMessage());
            e.printstacktrace();
            return false;
        } catch (IOException e) {
            Log.e(TAG,e.getMessage());
            e.printstacktrace();
            return false;
        }
    }

    public void stopRecording(){
        mediaRecorder.stop();
        camera.lock();
    }

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
    camera.stopPreview();
    previewRunning = false;
    camera.release();
}

}

记录是

08-31 02:20:11.781: E/MediaRecorder(14519): start Failed: -19
 08-31 02:20:11.781: D/AndroidRuntime(14519): Shutting down VM
 08-31 02:20:11.781: W/dalvikvm(14519): threadid=1: thread exiting with uncaught exception (group=0x416c9700)
 08-31 02:20:11.781: E/AndroidRuntime(14519): FATAL EXCEPTION: main
 08-31 02:20:11.781: E/AndroidRuntime(14519): java.lang.RuntimeException: start Failed.
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.media.MediaRecorder.start(Native Method)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at com.example.cameratest.MainActivity.startRecording(MainActivity.java:135)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at com.example.cameratest.MainActivity$2.onClick(MainActivity.java:61)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.view.View.performClick(View.java:4240)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.view.View$PerformClick.run(View.java:17721)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.os.Handler.handleCallback(Handler.java:730)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.os.Handler.dispatchMessage(Handler.java:92)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.os.Looper.loop(Looper.java:137)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at android.app.ActivityThread.main(ActivityThread.java:5103)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at java.lang.reflect.Method.invokeNative(Native Method)
08-31 02:20:11.781: E/AndroidRuntime(14519):    at java.lang.reflect.Method.invoke(Method.java:525)
08-31 02:20:11.781: E/AndroidRuntime(14519):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
08-31 02:20:11.781: E/AndroidRuntime(14519):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
 08-31 02:20:11.781: E/AndroidRuntime(14519):   at dalvik.system.NativeStart.main(Native Method)