camera.setPreviewDisplay（holder）;录制视频时通过Null指针异常

Question

在android中打开相机功能时，它引发了Null指针异常错误，并重定向到此行“ camera.setPreviewDisplay（holder）;”

该怎么办？

预览文件：   public void surfaceCreated（SurfaceHolderholder）{

    try {
        camera = Camera.open();

    } catch (Exception e) {
        Log.e("CameraVideoPOC", "failed to open Camera");
        e.printStackTrace();
    }

    try {
        camera.setPreviewDisplay(holder); // facing issue here
        camera.setPreviewCallback(new Camera.PreviewCallback() {

            public void onPreviewFrame(byte[] data, Camera arg1) {
                FileOutputStream outStream = null;
                try {
                    outStream = new FileOutputStream(String.format(
                            "/sdcard/%d.jpg", System.currentTimeMillis()));
                    outStream.write(data);
                    outStream.close();
                    Log.d(TAG, "onPreviewFrame - wrote bytes: "
                            + data.length);
                } catch (FileNotFoundException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                } finally {
                }
                Preview.this.invalidate();
            }
        });
    } catch (IOException e) {
        e.printStackTrace();
    }
}