Customize BarcodeDetector

[punksta]

What do you think about features:

• Use com.google.android.gms.vision.barcode.BarcodeDetector as singleton by default instead of creating new instance inside init() function. Do we really need different detectors in different readers?

class BarcodeDetectorHolder {
  private static  BarcodeDetector detector;

  static BarcodeDetector getBarcodeDetector(Context context) {
    if (detector == null)
      detector = new BarcodeDetector.Builder(context.getApplicationContext()).setBarcodeFormats(Barcode.QR_CODE).build();
    return detector;
  }
}

  public QREader(final Builder builder) {
    if (barcodeDetector == null)
      barcodeDetector = BarcodeDetectorHolder.getBarcodeDetector(builder.context);
   ...
   }

• Allow to set external BarcodeDetector to Builder. It can be useful, if someone will want to scan not only qr codes.

BarcodeDetector myDetector = ...; //set few barcode formats.
QRReader r = QREader.Builder(MainActivity.this, surfaceView, listener).setDetector(myDetector)

I already made it in my project and can make PR. But I'm not sure about first case.

[nisrulz]

@punksta I donot fully understand what you are proposing here. Can you provide me with more details.

[punksta]

@nisrulz added samples;

[nisrulz]

@punksta I think using Singleton would be a nice change as cases of having multiple instances of the same QREader class are very less.

However I would not want to extend QREader to start supporting other reading capability just because I made it specifically to read QRCodes. However there is no harm in providing a config function that open ups the functionality if its desired. The way of implementation should be in such a way that it does not alienate the api to deviate from its core cause of reading QRCodes.

Would love to hear your thoughts on this too.

[punksta]

@nisrulz I agree. Where is another case of supporting external BarcodeDetector: using one instance for scanning of locally images and using in your reader.