Using C++ Library in QML

Ravinder · wrote on 21 May 2012, 13:12

Hi All,

I want to use QZXing in my QML project for barcode scanning. Anyone have any idea how to use that. Thanx in advance.

leon.anavi · wrote on 21 May 2012, 13:22

Read the documentation of the "QZXing at Nokia Developer":https://projects.developer.nokia.com/QZXing

Ravinder · wrote on 22 May 2012, 07:05

I am following this link https://projects.developer.nokia.com/QZXing/wiki for using QZXing in qml. But i am not able to implement it successfully. Anyone have any idea how to do that.

sierdzio · wrote on 22 May 2012, 07:40

A bit more info, would be nice. Like where exactly are you failing, what is the error reported, etc.

Ravinder · wrote on 22 May 2012, 07:59

@ Sierdzio thnx for the rply. I am not able to incliding the QZXing.h file in my main C++ file. i had downloaded QZXing liberary from here https://github.com/zxing/zxing. And try to implement it according to this link https://projects.developer.nokia.com/QZXing/wiki , but i am unable to include QZXing.h .

sierdzio · wrote on 22 May 2012, 08:02

Mate, but what is the error message? Is there any? Also, what code (exactly) have you added to your .pro file? What platform are you targeting?

It's hard to help when I have to guess things, you know.

Ravinder · wrote on 22 May 2012, 08:52

Actually i am working on QT Quick. And using Qt Quick 4.7 . And i had added that library in .pro file. Below is the code snip set of .pro file.

Add more folders to ship with the application, here

folder_01.source = qml/QMLBarcodeScanner
folder_01.target = qml
DEPLOYMENTFOLDERS = folder_01

Additional import path used to resolve QML modules in Creator's code model

QML_IMPORT_PATH =

symbian:TARGET.UID3 = 0xE35E8B99

Smart Installer package's UID

This UID is from the protected range and therefore the package will

fail to install if self-signed. By default qmake uses the unprotected

range value if unprotected UID is defined for the application and

0x2002CCCF value if protected UID is given to the application

#symbian:DEPLOYMENT.installer_header = 0x2002CCCF

Allow network access on Symbian

#symbian:TARGET.CAPABILITY += NetworkServices

If your application uses the Qt Mobility libraries, uncomment the following

lines and add the respective components to the MOBILITY variable.

CONFIG += mobility

MOBILITY +=

Speed up launching on MeeGo/Harmattan when using applauncherd daemon

CONFIG += qdeclarative-boostable

Add dependency to Symbian components

CONFIG += qt-components

The .cpp file which was generated for your project. Feel free to hack it.

SOURCES += main.cpp

symbian{
LIBS += -lqzxing
customrules.pkg_prerules =
";QZXing"
"@"$$(EPOCROOT)Epoc32/InstallToDevice/QZXing_selfsigned.sis",(0xE618743C)"
" "
DEPLOYMENT += customrules
}

win32{
LIBS += -LC:/QtSDKProjects/QMLBarcodeScanner/Qt_4.7.4_Desktop_Mingw
-lQZXing
}

Please do not modify the following two lines. Required for deployment.

include(qmlapplicationviewer/qmlapplicationviewer.pri)
qtcAddDeployment()

Now i think u will able to help me.

sierdzio · wrote on 22 May 2012, 08:58

Thanks, that is much better.

Seems you forgot to include this line:
@
INCLUDEPATH += "absolute path of the folder where the files where placed"
@

This is probably why you cannot include the file - without include path set, compiler does not "see" the header of qzxing lib.

Ravinder · wrote on 22 May 2012, 09:09

Now library is added in project but it is given this error on compile time :

*d:/qt/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: cannot find -lQZXing
collect2: ld returned 1 exit status
mingw32-make.exe[1]: *** [debug\QMLBarcodeScanner.exe] Error 1
mingw32-make.exe: *** [debug] Error 2
14:38:25: The process "D:\QT\mingw\bin\mingw32-make.exe" exited with code 2.
Error while building project QMLBarcodeScanner (target: Qt Simulator)
When executing build step 'Make' *

sierdzio · wrote on 22 May 2012, 09:13

Is the library compiled?

Also, the wiki seems to differ between -lQZXing and -lQZXing_selfsigned - maybe you are linking against wrong library?

Ravinder · wrote on 22 May 2012, 09:27

I download the library from here: https://github.com/zxing/zxing and i think this is compiled. And this is my .pro file code :

symbian{
LIBS += -lqzxing
customrules.pkg_prerules =
";QZXing"
"@"$$(EPOCROOT)Epoc32/InstallToDevice/QZXing_selfsigned.sis",(0xE618743C)"
" "
DEPLOYMENT += customrules
}

win32{
LIBS += -LC:/QtSDKProjects/QMLBarcodeScanner/Qt_4.7.4_Desktop_Mingw
-lQZXing
INCLUDEPATH += "D:\QT\Symbian\SDKs\Symbian3Qt474\epoc32\include"
}

and i think u will able to solve it out this time.

sierdzio · wrote on 22 May 2012, 09:35

Whoa! In both INCLUDEPATH and LIBS, you point to Qt installation! Those have to point to files in your QZXing installation (headers/ compiled dlls respectively), so that compiler (and qmake) knows where to fine both the qzxing.h and qzxing.so (or .dll, or .a, depending on platform and a few other things). If your project needs both includes, you can include more paths just like in "SOURCES" calls ("" to break the line, then add another entry)

Ravinder · wrote on 22 May 2012, 10:21

@ Sierdzio, Thnx for your precious time...i am able to run my project on simulator but not able to run it on my nokia symbian bele (NOKIA 603). It is giving error:

Error while building project QMLBarcodeScanner (target: Symbian Device) When executing build step 'qmake'

sierdzio · wrote on 22 May 2012, 10:47

Good to know we made some progress, but I am afraid my help will have stop here - I have no experience in developing on Symbian.

The only thing that comes to my mind is that - maybe - you have to copy the library to the symbian device, too. But that is just a guess, I really don't know anything about Symbian.

Ravinder · wrote on 22 May 2012, 13:51

Hi all,

I am able to access QZXing for the simulator . But when it comes for Symbian device it is not accessible
I think there is a problem from the symbian target in my .pro file. Below is the code snip shot of my .pro file for symbian is:

_ LIBS += -lqzxing
customrules.pkg_prerules =
";QZXing"
"@"$$(EPOCROOT)Epoc32/InstallToDevice/QZXing_selfsigned.sis",(0xE618743C)"
" "
DEPLOYMENT += customrules_

This declaration is same as given here : https://projects.developer.nokia.com/QZXing/wiki

But in my case the the library is not included.

Thnx for any help in advance.

favoritas37 · wrote on 7 Jun 2012, 08:29

Your first problem is that your project folder is in a different disk drive compared to the disk drive that the Symbian SDK is installed. Symbian toolchain requires that the projects built must be in the same drive as the Symbian SDK so first fix that.

Moreover the following code is unnecessary when building for Symbian since that path is already included. That is why the project's wiki says to copy the binaries in the epoc32 folder.
@
INCLUDEPATH += “D:\QT\Symbian\SDKs\Symbian3Qt474\epoc32\include”
@

One note here is that i am a bit curious on how, as you say, it works for Qt Simulator. I haven't supported it event though it can be done with some modifications.

Finally, if you are getting error when qmake is executed this means that there is a syntax error in your .pro file. If you are still experiencing the same error post the .pro but included in the code tags (place a "@" at the beginning and end of the code ).

favoritas37 · wrote on 7 Jun 2012, 13:32

This thread is continued "here":http://qt-project.org/forums/viewthread/17435/.