ANDROID ZXING: Saving a photo in onPreviewFrame saves a photo every frame. How to only save a single photo upon scan?

问题

For the last few weeks I have been attempting to alter Zxing to take a photo immediately upon scan. Thanks to help I am at a point where I can be consistently saving an image from the onPreviewFrame class within PreviewCallback.java

The code I use within the onPreviewMethod method shall follow, and then a short rundown of how my app works.

public void onPreviewFrame(byte[] data, Camera camera) {
Point cameraResolution = configManager.getCameraResolution();
Handler thePreviewHandler = previewHandler;

android.hardware.Camera.Parameters parameters = camera.getParameters();
android.hardware.Camera.Size size = parameters.getPreviewSize();

int height = size.height;
int width = size.width;

System.out.println("HEIGHT IS" + height);
System.out.println("WIDTH IS" + width);



if (cameraResolution != null && thePreviewHandler != null) {


    YuvImage im = new YuvImage(data, ImageFormat.NV21, width,
            height, null);
            Rect r = new Rect(0, 0, width, height);
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            im.compressToJpeg(r, 50, baos);

            try {
                FileOutputStream output = new FileOutputStream("/sdcard/test_jpg.jpg");
                output.write(baos.toByteArray());
                output.flush();
                output.close();

                System.out.println("Attempting to save file");
                System.out.println(data);

            } catch (FileNotFoundException e) {

                System.out.println("Saving to file failed");

            } catch (IOException e) {

                System.out.println("Saving to file failed");

            }


    Message message = thePreviewHandler.obtainMessage(previewMessage, cameraResolution.x,
      cameraResolution.y, data);
  message.sendToTarget();
  previewHandler = null;

} else {
  Log.d(TAG, "Got preview callback, but no handler or resolution available");
}}

My application centers around its own GUI and functionality, but can engage Zxing via intent (Zxing is built into the apps build path, yes this is bad as it can intefere if Zxing is already installed). Once Zxing has scanned a QR code, the information encoded on it is returned to my app and stored, and then after a short delay Zxing is automatically re-initiated.

My current code saves an image every frame whilst Zxing is running, the functionality I would like is to have only the frame on scan be saved. Although Zxing stops saving images in the short window where my app takes over again, Zxing is quickly re-initialized however and I may not have time to manipulate the data. A possible workaround however is quickly renaming the saved file so that Zxing doesn't start overwriting it and manipulation can be performed in the background. Nevertheless, saving an image every frame is a waste of resources and less than preferable.

How do I only save an image upon scan?

Thanks in advance.

---

Updated to show found instances of multiFormatReader as requested:

private final CaptureActivity activity;
private final MultiFormatReader multiFormatReader;
private boolean running = true;
DecodeHandler(CaptureActivity activity, Map<DecodeHintType,Object> hints) {
multiFormatReader = new MultiFormatReader();
multiFormatReader.setHints(hints);
this.activity = activity;
}
@Override
public void handleMessage(Message message) {
if (!running) {
  return;
}
if (message.what == R.id.decode) {
    decode((byte[]) message.obj, message.arg1, message.arg2);
} else if (message.what == R.id.quit) {
    running = false;
    Looper.myLooper().quit();
}}
private void decode(byte[] data, int width, int height) {
long start = System.currentTimeMillis();
Result rawResult = null;
PlanarYUVLuminanceSource source = activity.getCameraManager().buildLuminanceSource(data, width, height);
if (source != null) {
  BinaryBitmap bitmap = new BinaryBitmap(new HybridBinarizer(source));

  //here?

  try {
    rawResult = multiFormatReader.decodeWithState(bitmap);
  } catch (ReaderException re) {
    // continue
  } finally {
    multiFormatReader.reset();
  }
}

回答1:

ZXing detects every received frame until finds out correct information. The image saving point is when ZXing returns a string which is not null. In addition, you can save file with different name "timestamp + .jpg", in case previous file will be overwritten.

来源：https://stackoverflow.com/questions/18232992/android-zxing-saving-a-photo-in-onpreviewframe-saves-a-photo-every-frame-how-t