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[Solved] QApplication: No such file or directory

  • I got Qt5 installed on Opensuse 12.2.
    I tried to compile some example project that compiled successfully on Qt 4.8.
    Now I get error message "QApplication: No such file or directory"
    I think the PATH to library is missing while I installed locally on /home/

    Where should I edit?

  • Moderators

    How do you include QApplication header? In Qt5, it resides in <QtWidgets/QApplication>, while in Qt4 it was <QtGui/QApplication>.

  • I think the module isn't added in .pro file, so did you added QT += widgets in your .pro file?

    //anyway if the module is added the header can be included with #include <QApplication> you don't need <QtWidgets/QApplication> or <QtGui/QApplication> in Qt4 (that works with both Qt4 and 5)

  • Adding QT += widgets in .pro file made the trick. Thanks.

  • Why does qmake not include these, or what must one do in the source to ensure qmake auto generates this line in the .pro file ?

  • Moderators

    qmake will never generate anything in your .pro file. Those files are config files for qmake to use, not the other way around. If you create a new project in recent versions of Qt Creator, this line will be added for you in standard app template.

  • Ooh ok, that make more sense now, thanks for the reply.

    Sorry for hijacking the thread by the way :D

  • The "Adding QT += widgets in .pro file" really helped me as well. Thanks.

  • I'm happy, too. I solved.

    Why qmake --project is doing a so simple task in a wrong way?

  • can qmake -project add "QT += widgets" to .pro automatically ?

  • Just to say what happened to be my problem, it was a dumb error:

    I was following a guide that had me open an empty QT project, which gave me a .pro file but left it empty. I had filled in some data and "TEMPLATE = application" as they has mentioned it. I already had the "widgets" line but it still couldn't find the library as I included it in the .cpp file. When I changed it to "TEMPALTE = app" the .pro file was parsed, and the file to include resolved correctly (QApplication).

  • @sierdzio
    I have add <QtWidgets/QApplication> to mainwindow.h file and
    QT += widgets in .pro file but still "error : No such file or directory" occurs .

  • Lifetime Qt Champion

    @Mijaz said in [Solved] QApplication: No such file or directory:



    #include <QApplication>

  • @jsulm
    I have changed but error still error not resolved.

  • Lifetime Qt Champion

    @Mijaz Please show your pro file and main.cpp

  • @jsulm Hello, I am having a similar issue to @Mijaz. I am trying to use Qt 5.11 to cross compile for a STM32MP157c-DK2 development board. I have successfully loaded images to the board from a qml file but my cpp files are riddled with errors including "use of undeclared identifier 'QCoreApplication'. I have tried adding #include <QApplication> and QT += widgets with no luck. Here is my main.cpp file and my pro file.


    #include <QGuiApplication>
    #include <QQmlApplicationEngine>
    #include <QApplication>
    #include <QLabel>
    #include <QQmlEngine>
    #include <QTextCodec>
    #include <QtGui>
    int main(int argc, char *argv[])
        QGuiApplication app(argc, argv);
        QQmlApplicationEngine engine;
        const QUrl url(QStringLiteral("qrc:/main.qml"));
        QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                         &app, [url](QObject *obj, const QUrl &objUrl) {
            if (!obj && url == objUrl)
        }, Qt::QueuedConnection);
        return app.exec();

    pro file

    QT += quick widgets core gui
    CONFIG += c++11 qmltypes qt
    # The following define makes your compiler emit warnings if you use
    # any Qt feature that has been marked deprecated (the exact warnings
    # depend on your compiler). Refer to the documentation for the
    # deprecated API to know how to port your code away from it.
    # You can also make your code fail to compile if it uses deprecated APIs.
    # In order to do so, uncomment the following line.
    # You can also select to disable deprecated APIs only up to a certain version of Qt.
    #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
    SOURCES += \
    RESOURCES += qml.qrc
    # Additional import path used to resolve QML modules in Qt Creator's code model
    # Additional import path used to resolve QML modules just for Qt Quick Designer
    # Default rules for deployment.
    #qnx: target.path = /tmp/$${TARGET}/bin
    #else: unix:!android: target.path = /opt/$${TARGET}/bin
    #!isEmpty(target.path): INSTALLS += target
    TARGET = stm32mp1Test
        target.files = stm32mp1Test
        target.path = /home/root
    INSTALLS += target

    Thanks for the help.

  • Lifetime Qt Champion

    @braden_sun Did you cross compile Qt for your device?
    Why do you include QApplication and QGuiApplication if you want to use QCoreApplication? You need to include QCoreApplication...

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