Use QZXing in qml

[MHermann]

Hi all,

at the moment I am trying to use QZXing in my qml.
But I am failing.
If I try to compile I get the following error: "undefined reference to 'QZXing::registerQMLTypes()'"
But decoding the qr code of an image in main() works.

What I have done so far:

• Downloaded QZXing source and compiled it to get libQZXing.so.

• xxx.pro file:

  QT += core gui qml quick widgets multimedia
  ...
  LIBS += -L$$PWD/QZXing/ -lQZXing
  INCLUDEPATH += $$PWD/QZXing
  DEPENDPATH += $$PWD/QZXing
  

• main.cpp:

  #include <QGuiApplication>
  #include <QQmlApplicationEngine>
  #include <QZXing.h>
  
  int main(int argc, char *argv[])
  {
      QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
      QGuiApplication app(argc, argv);
  
      QZXing::registerQMLTypes();
      QQmlApplicationEngine engine;
      engine.load(QUrl(QLatin1String("qrc:/main.qml")));
      if (engine.rootObjects().isEmpty())
          return -1;
  
      QImage qrCodeimageToDecode("/xxx/qrcode.png");
      QZXing decoder;
      decoder.setDecoder(QZXing::DecoderFormat_QR_CODE);
      QString resultQrCode = decoder.decodeImage(qrCodeimageToDecode);
  
      return app.exec();
  }
  

Any ideas what I am doing wrong?

[raven-worx]

@MHermann said in Use QZXing as library in qml:

Any ideas what I am doing wrong?

are you sure the libQZXing.so relies in $$PWD/QZXing/ ??

[MHermann]

@raven-worx : Yes, I compiled it and copied it there.

[MHermann]

@raven-worx :
The three lines

QZXing decoder;
decoder.setDecoder(QZXing::DecoderFormat_QR_CODE);
QString resultQrCode = decoder.decodeImage(qrCodeimageToDecode);

are executing without problems. And they are also used from libQZXing.so.

[raven-worx]

@MHermann

are executing without problems. And they are also used from libQZXing.so.

Yes i overread that.

seems the QZXING_QML macro definition is missing.
Recompile the lib with CONFIG += qzxing_qml

[MHermann]

@raven-worx :
I added the line

CONFIG += qzxing_qml

to QZXing.pro and compiled the lib again.

I copied the new *.so files to my directory.
But it behaves exactly the same...
"undefined reference to `QZXing::registerQMLTypes()'"

I forgot to mention, that I also added additional arguments in my project:

DEFINES+=QZXING_QML DEFINES+=QML_MULTIMEDIA

Any more ideas?

[raven-worx]

@MHermann said in Use QZXing as library in qml:

Any more ideas?

No, this seemed pretty much the cause for issue to me.

Alternatively - if its's an option for you - you could add include($$PWD/QZXing/src/QZXing.pri (and also add CONFIG += qzxing_qml) to your application's .pro file. Then QZXing is compiled into your binary directly.

[MHermann]

@raven-worx :

This could also be a solution. But this would not be my preferred solution...
That would mean that the whole QZXing source code will be compiled too, each time I am compiling my own source code.
Or is it possible to exclude this from the compiling process and compile it only once?

[raven-worx]

@MHermann
it gets only recompiled when it needs to (when a source file changes, etc)

[MHermann]

@raven-worx :

I added the QZXing source code via

include($$PWD/QZXing/src/QZXing.pri

Now it is working.

[lukas_kosinski]

Hi! If your project is based on C++, consider using SCodes. SCodes uses latest ZXing C++ port. It also allows you to generate QR/Bar codes. You can read more about it here.

[ekkescorner]

@lukas_kosinski unfortunately SCodes only supports Code128 and QR

[lukas_kosinski]

@ekkescorner I worked on that and now it supports much more formats. Currently it's a PR opened, but it should be soon merged:
https://github.com/scytheStudio/SCodes/pull/11

Sorry that I add the comment to a quite old post. I simply wanted people to know it and not be misled.