Even though I declared QT += multimedia multimediawidgets in my .pro file I am getting error Undefined reference to QMediaPlayer and QVideoWidget constructors, destructors and methods, I included path in my .pro file to those files in /usr/include/QtMultimetiaKit like this INCLUDEPATH += /usr/include/QtMultimediaKit/, but errors are the same, what else to try?
I am running Qt 4.8.6 and Qt Creator 3.5.1 on Ubuntu 14.04.3.
You need to add to the .pro file:
CONFIG += mobility
MOBILITY += multimedia
Related
I'm currently learning how to use Qt. I want to try out some simple image processing applications using Qt, and since I'm already familiar with CImg I want to use that. I guess it should be possible to do so, if not mark my question for deletion or something.
My question is: how to get CImg working for Qt? CImg is a header file. Lets say its located on my desktop. I import it using Qt creator 4.1.0, by using the "add existing file..." in the rightclick menu on the header folder. Then my menu looks like this:
.
It compiles when I add #include "CImg.h", but I can't use it, even when I'm trying to type using namespace cimg_library it will tell me that cimg_library doesn't exist. I also tried just creating a header file and copying the content of the CImg.h into it but then it simply fails to compile and the Qt Creator freezes.
Edit: I managed to make the situation a bit better by adding the header location to the include code (like this: #include "C:/Users/Marci/Desktop/CImg.h" )I can now "see" CImg related stuff in the dev environment, and it won't bother me with not finding the constructor for CImg or anything like that. However when I try to compile while using anything CImg related it will give me around 20 linker errors. (Error code: LNK2019) My .pro file looks like this:
#-------------------------------------------------
#
# Project created by QtCreator 2016-11-08T17:08:58
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = grayscale
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h \
C:/Users/Marci/Desktop/CImg.h
LIBS += -C:/Users/Marci/Desktop/ -CImg.h
FORMS += mainwindow.ui
Edit2: after implementing the changes that PeterT suggested in his comment my .pro file looks like this:
#-------------------------------------------------
#
# Project created by QtCreator 2016-11-08T17:08:58
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = grayscale
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h \
INCLUDEPATH += C:/Users/Marci/Desktop
FORMS += mainwindow.ui
And my mainwindow.cpp (in which i'm trying to create a CImg object) looks like this:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <CImg.h>
using namespace cimg_library;
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
CImg<unsigned char> myimage(100,200);
}
MainWindow::~MainWindow()
{
delete ui;
}
The compiler errors i get are: error: C2871: 'cimg_library': a namespace with this name does not exist
error: C2065: 'CImg': undeclared identifier
error: C2062: type 'unsigned char' unexpected
I hope this is specific enough.
After I few months I figured it out. The problem lies in the fact, that CImg uses a windows .dll file for the visualizing functions of the class cimg_display. Since Qt is platform independent it doesnt like this. However you can make it work with an interesting trick. First you need to include the header file normally, in the project file. After that, whenever you actually #include it, you need to write the following macro:
#define cimg_display 0
In my understanding this makes it work, because the C and C++ compilers simply copy the content of the included file into the source. And thanks to the macro the compiler will ignore the class thats causing trouble for us.
I created this simply application in Qt4 and would like to test it on RH Linux distro. The distro has both QtCore "Qt4" and Qt3 installed. I cannot add or delete any of these Qt versions, but would like to work with what's available.
I have an error compiling my windows based Qt program "Qt4" in Linux .
First question :
- How do I compile my compile in Linux without QT creator "only Qt libraries" are installed, what I did is get the .pro file from windows and typed qmake . , the errors are :
WARNING : Found potential symbol conflict of mainwindow.cpp (mainwwindow.cpp) in SOURCES
WARNING : Found potential symbol conflict of mainwindow.h (mainwwindow.cpp) in HEADERS
WARNING : Found potential symbol conflict of dialog.cpp (dialog.cpp) in SOURCES
WARNING : Found potential symbol conflict of dialog.h (dialog.h) in HEADERS
How can I modify qmake to specify the version of Qt
Thank you.
Below is my .pro file
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = TestTool
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp \
dialog.cpp
HEADERS += mainwindow.h \
dialog.h
FORMS += mainwindow.ui \
dialog.ui
The compilation error is :
Try using the Qt4 version of qmake explicitly:
/usr/lib64/qt4/bin/qmake -o Makefile TestTool.pro
I've read all other answers and try to follow but still got the error.
I use Qt 4.8.6 and QT creator 3.5.1. I include libproj in the .pro file:
INCLUDEPATH += C:/Qt/include/libproj-4.4
LIBS += -LC:/Qt/lib -lproj
The libproj.a is available in the specified dir, and src code is also available.
The header file is included in Projection.h:
extern "C" {
#include <proj_api.h>
}
The function "pj_free" is called in Projection_libproj.cpp
Then I got the error:
C:\Users\ngu\Documents\jan-mayen\JanMaven\src\map\Projection_libproj.cpp:-1: error: undefined reference to `pj_free'
Windows 7
Qt 5.4.0
OpenCV 2.4.10
Mingw 4.9.1
I'm trying to create a simple Hello World app, to test if Qt is working with OpenCV. Besides the stuff created by default, the code is
#include <opencv/cv.h>
#include <opencv/highgui.h>
(...)
cv::Mat image= cv::imread("pic.jpg");
cv::namedWindow("Test picture");
cv::imshow("Test picture", image);
cv::waitKey(1000);
(...)
However, I'm having trouble linking libraries. At first I've set the paths to *.dll.a files manually
INCLUDEPATH += C:/opencv/my_build/install/include
INCLUDEPATH += C:/opencv/my_build/install/include/opencv
INCLUDEPATH += C:/opencv/my_build/install/include/opencv2
LIBS += -LC:/opencv/my_build/install/x86/mingw/lib \
-llibopencv_core2410 \
-llibopencv_highgui2410
etc etc
But then I'd get a cannot find -llibopencv_<lib>2410 error. I've even used Qt Creator's "Add library" function (Projects -> rightclick -> add library), the result is the same. That error only goes away if I change -llibopencv_<lib>2410 to -opencv_<lib>2410. Which from my understanding is weird, as the "l" argument is missing.
Even though that error goes away, a bunch of others replace it, as I get undefined reference to cv::EVERYTHING error. I've looked around, found solutions to either problem, but solving one leads to the other and vice versa.
I'm fairly sure the OpenCV build is not at fault - I've already completed a pretty big console-ish app using it with Code::Blocks.
My current *.pro file :
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = OpenCVTest
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
INCLUDEPATH += C:/opencv/my_build/install/include
win32: LIBS += -L$$PWD/../../../../../../OpenCV/my_build/install/x86/mingw/lib/ -llibopencv_core2410
INCLUDEPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
DEPENDPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
win32: LIBS += -L$$PWD/../../../../../../OpenCV/my_build/install/x86/mingw/lib/ -llibopencv_highgui2410
INCLUDEPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
DEPENDPATH += $$PWD/../../../../../../OpenCV/my_build/install/x86/mingw
How to correctly link the OpenCV libraries to Qt Creator? Am I missing something?
edit: I've rebuilt the whole damn thing and it still doesn't work. God damn it.
When specifying library, you need to exclude the 'lib' part:
LIBS += -LC:/opencv/my_build/install/x86/mingw/lib \
-lopencv_core2410 \
-lopencv_highgui2410
Frankly, I have little idea of what went wrong. I've edited the environment PATH variable, twice, to include the OpenCV build. Maybe I've made a typo the first time. It now looks like this:
C:\MinGW\bin;C:\OpenCV\my_build\install\x86\mingw\bin;C:\Qt\5.4.0\5.4\mingw491_32\bin;
My *.pro file also looks different.
QT += core
QT -= gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = OpenCVTest
CONFIG += console
CONFIG -= app_bundle
TEMPLATE = app
INCLUDEPATH += C:/OpenCV/qtbuild//install/include
LIBS += "C:/OpenCV/qtbuild/install/x86\mingw/lib/*.a"
SOURCES += main.cpp\
mainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
I've change +=gui to -=gui and added CONFIG -= app_bundle. The INCLUDE and LIBS paths are also different now - I won't be changing them out of an irrational fear something will go horribly wrong again.
And lastly, I've simply removed the previous project and made a new one. Maybe something else got corrupted?
Anyway, it works now, after doing these things.
I am a bit stuck at the moment with a little sample project that I would like to run to test some cryptology that I want to use in a main project.
Basically I am using the latest Qt Creator and I have created a simple window dialog. Furthermore, I would like to test the PBKDF2 implementation through CkCrypt2
So what I have done is downloading the X64 version of the library and added it to my project folder. I then told my Qt project to use an external library, the final .pro file looks like this:
#-------------------------------------------------
#
# Project created by QtCreator 2013-06-09T18:09:44
#
#-------------------------------------------------
QT += core gui
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = crypt2test
TEMPLATE = app
SOURCES += main.cpp\
m
ainwindow.cpp
HEADERS += mainwindow.h
FORMS += mainwindow.ui
win32:CONFIG(release, debug|release): LIBS += -L$$PWD/libs/ -lChilkatDbgDll_x64
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/libs/ -lChilkatDbgDll_x64d
else:unix: LIBS += -L$$PWD/libs/ -lChilkatDbgDll_x64
INCLUDEPATH += $$PWD/include
DEPENDPATH += $$PWD/include
I can successfully load the library but I cannot start the application.
My mainwindow.cpp looks like this:
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "CkCrypt2.h"
#include <QDebug>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
CkCrypt2 crypt;
bool success;
success = crypt.UnlockComponent("Just some random text ");
if ( !success )
{
qDebug() << "Not successfully unlocking the library";
}
}
MainWindow::~MainWindow()
{
delete ui;
}
The error message I get in the compiler is:
c:\qt\qt5.0.2\tools\qtcreator\bin\crypt2test\include\CkString.h:127: error: C2061: syntax error : identifier 'SYSTEMTIME'
c:\qt\qt5.0.2\tools\qtcreator\bin\crypt2test\include\CkString.h:129: error: C2061: syntax error : identifier 'SYSTEMTIME'
C:\Qt\Qt5.0.2\Tools\QtCreator\bin\crypt2test\include\CkCrypt2.h:429: error: C2061: syntax error : identifier 'SYSTEMTIME'
Looking into the files I see:
void appendDateRfc822(SYSTEMTIME &sysTime);
void appendDateRfc822Gmt(SYSTEMTIME &sysTime);
// GETSIGNATURESIGNINGTIME_BEGIN
bool GetSignatureSigningTime(int index, SYSTEMTIME &outSysTime);
// GETSIGNATURESIGNINGTIME_END
Okay, so it is complaining about the SYSTEMTIME construct. So I look up the error C2061
Basically it says:
The compiler found an identifier where it wasn't expected. Make sure
that identifier is declared before you use it.
Which makes sense, so I look up the SYSTEMTIME and try to do :
#include <windows.h>
But that leads to many more errors in the windows.h file itself.
I use the MS Visual C++ compiler in Qt. Even though I use qmake. I am very new to this and I do not understand it all yet. Furthermore, I have no idea how to fix this, because including the windows.h does not help.
What seems to be the problem here ? Is this an issue regarding my compiler or the constulation that I use a third party app which library is compiled with MS Visual C++ and I am now trying to use this on my Windows machine in Qt with a Windows Visual C++ compiler ?
For any help I am gratefully thankful!
EDIT1:
Actually, after a clean all and qmake and build project I have now different errors and none were found in the Windows.h as previously stated. Since there were so many I have made a screenshot: http://i.imgur.com/B8EoENB.png
EDIT2:
I have adjusted the library that I include. Before this I was using the multi-threaded library of CkCrypt in the Debug mode. I have now included the single realease library. Which is located in the same directory.
When including windows.h I got the errors that things were already defined. So I removed the line again. With this result: http://i.imgur.com/z415txR.png
This shows at the bottom that MSVCRT conflichts with other library. It mentions to use NODEFAULTLIB:library but I am not to sure how to do that. Will google and keep this up to date as I process.
Many years ago, Chilkat was originally developed for the Windows platform only, and used SYSTEMTIME for this reason. In the last 5 years (approx) Chilkat is cross-platform, and SYSTEMTIME no longer makes sense. To cope with the issue, there is a "SystemTime.h" header in the same directory as the CkCrypt2.h header file. You could include this to solve the problem. (However, if WIN32 is defined, you'll probably need to edit SystemTime.h to remove the #ifdef.)
In any case, the methods using SYSTEMTIME are going to be deprecated. For any method or property that uses SYSTEMTIME, there should be a newer alternative method/property that instead uses CkDateTime.
Finally, Chilkat will test with Qt so that for the next version, (hopefully) Qt out-of-the-box will compile without any pitfalls.