Qt/Qt Designer (Version 3.x) GUI questions



  • Greetings,

    I am very new to Qt/Qt Designer (version 3 on a RHEL 5.x). Please bare with me.

    I am trying to put together a simple GUI on QT Designer as follows:

    1. A bottom row of pushbuttons (selected from QT Designer)
    2. A "textlabel" rectangle (also selected from QT Designer) on top of the pusbuttons. I would like to "paste/insert" a pre-crafted GIF/PNG pre-image file inside the textlabel in 2)

    What I am looking to do with QT Designer (or manually coded through QT development package) is to select a different GIF file to insert in the rectangle 2) above for each of the pushbuttons I have. That is:

    1. Insert GIF1 into 2) when push-button 1 is pressed
    2. ...
      N) Insert GIFN into 2) when push-button N is pressed.

    Please reply.

    Thank you all,
    Qt-Newbie


  • Moderators

    have a look at "QSignalMapper":http://doc.qt.nokia.com/4.7/qsignalmapper.html#details

    It exists also for Qt3 but in the old docs you don't have this example.

    use @setIcon@ to set the GIF and you can use smart QString to find the right one.

    If you have more specific questions you're welcome to ask ;)



  • Eddy,

    Thanks for your reply and your offer. I will likely have further questions on signal mapping depending on how I fare.

    Do I use "uic" tool in the QT package to convert QT Designer's .ui file (for my basic GUI layout with the widgets) to C++ source code ? Any insights on the ease of development between QT Designer and hand-coding ?

    Thanks,

    QT-Newbie



  • Greetings,

    Is the "setIcon" method in "QAction Class" or is it from another QT Class API ?

    Thanks,
    Qt-Newbie


  • Moderators

    [quote author="qt-newbie" date="1312387258"]Greetings,

    Is the "setIcon" method in "QAction Class" or is it from another QT Class API ?

    Thanks,
    Qt-Newbie
    [/quote]

    Sorry I didn't make myself clear. It's a method of QPushButton.



  • [quote author="qt-newbie" date="1312386007"]
    Do I use "uic" tool in the QT package to convert QT Designer's .ui file (for my basic GUI layout with the widgets) to C++ source code ? Any insights on the ease of development between QT Designer and hand-coding ?[/quote]

    Yes that's the way it works, both with Qt3 and Qt4.

    If you put the names of the ui files to the FORMS variable in your .pro file, this step will be executed automatically for you. You will have to include the resulting header file, that contains the implementation in some of your headers.

    See the "Qt Designer 3.3":http://doc.qt.nokia.com/3.3/designer-manual.html documentation for the gory details.

    Just another question: Are you forced to use Qt3 by any means? If not, you should strongly consider to start your development with Qt4. Qt3 is not maintained actively any more and the sources for help will decrease over time. And of course you save yourself the work of converting later on :-)


  • Moderators

    [quote author="qt-newbie" date="1312386007"]Eddy,
    Do I use "uic" tool in the QT package to convert QT Designer's .ui file (for my basic GUI layout with the widgets) to C++ source code ? Any insights on the ease of development between QT Designer and hand-coding ?
    Thanks,
    QT-Newbie[/quote]

    Have a look in the "Qt Designer manual":http://doc.qt.nokia.com/3.3/designer-manual-6.html.

    Also, please use Qt instead of QT(= QuickTime) and you will make even more friends here ;)



  • Volker,

    Thanks for your reply.

    I am using QT3.3 as it is installed by default in RHEL 5.4. I am not sure if QT4 is supported in it. As my project is in a hyper-drive schedule (and I started a few days ago), I am trying to minimize risk by sticking to the defaults.

    Question to all: Is there any simple example from QT3 I can use which shows the use of QSignalMapper (with the setIcon method in QPushButton) as pointed out by Eddy ?

    Any simple example (or links) are welcomed.

    Thanks,

    • QT-Newbie

  • Moderators

    The link to the QSignalmapper docs I gave you has an example that is similar to what you want. I suggest you start with it and then use the setIcon method later on.

    You can ask specific questions as you proceed. If you show us some code of what you accomplished it's easier to help.



  • Then please switch to Qt4. You can always get the sources from the "Qt download pages":http://qt.nokia.com/downloads/downloads#qt-lib (get the as tar.gz) and compile Qt yourself, it's only a matter of a

    @
    ./configure
    make
    sudo make install
    @

    combo.

    Qt3 is outdated and definitely not recommended for new projects - only use it if you absolutely must. Qt5 is in a rise already!



  • All,

    I have made the switch to Qt 4. However, I have scoured over Qt , TrollTech and Nokia pages, examples and web search resources to to attempt finding a Qt4 example tied to my application and I simply cannot find one.

    I am in urgent need of a simple example showing the following (hand-code C++ would be OK):

    1. A widget (on top) where a GIF file can be loaded and displayed within it (the GIF files are externally crafted, so that's not a problem)

    2. Two push-buttons (below the widget in 1) ) horizontally placed. Each push-button loads a separate GIF:

    • push-button 1 loads GIF # 1 in 1)
    • push-button 2 loads GIF # 2 in 1)

    Eddy: You mentioned using QSignalMapper in Qt 4 with setIcon and the smarts on QString to find the right GIF files. I cant' seem to locate it in the examples section of Qt 4. Can you show me a really simple example or send me the code you refer to ?

    All: I really need your help.

    Thank you very much,

    Qt-Newbie


  • Moderators

    this is the "link":http://doc.qt.nokia.com/4.7/qsignalmapper.html#details I gave you. It still works ;)
    I know it's not exactly what you want to do but it gives you a good start.

    What do you have so far?



  • consider the following:
    @
    //in mylabel.h
    class MyLabel : public QLabel
    {
    Q_OBJECT

    public slots:
    void setFileName(QString name)
    {
    setPixmap(name);
    }
    };

    //in main.cpp
    int main(int argc, char *argv[])
    {
    QApplication app(argc, argv);

     QSignalMapper mapper;
     MyLabel label;
     QPushButton b1;
     QPushButton b2;
     mapper.setMapping(&b1,"gif1.gif");
     mapper.setMapping(&b2,"gif2.gif");
     QObject::connect(&b1,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&b2,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&mapper,SIGNAL(mapped(QString)),&label,SLOT(setFileName(QString)));
     label.show();
    
     return app.exec();
    

    }

    @



  • Eddy, Loladiro,

    Thanks very much for your replies.

    Loladiro: I will start with your code and let you know how I fare.

    Qt-Newbie



  • There was a copy&paste error in my code.
    I had
    @
    mapper.setMapping(&b2,"gif2.gif");
    @
    twice. It's fixed now.



  • Loladiro,

    I took your code and made some mods to it so that it would compile without errors using Qt 4.2.1. Here they are:

    1. mylabel.h

    @
    #ifndef MYLABEL_H
    #define MYLABEL_H

    #include <QLabel>

    //in mylabel.h
    class MyLabel : public QLabel
    {
    Q_OBJECT

    public slots:
    void setFileName(QString name)
    {
    setPixmap(name);
    }
    };

    #endif
    @

    1. Also, made some mods to main.cpp:

    @
    #include <QApplication>
    #include <QSignalMapper>
    #include <QPushButton>

    #include "mylabel.h"

    //in main.cpp
    int main(int argc, char *argv[])
    {
    QApplication app(argc, argv);

     QSignalMapper mapper;
     MyLabel label;
     QPushButton b1;
     QPushButton b2;
     mapper.setMapping(&b1,"gif1.gif");
     mapper.setMapping(&b2,"gif2.gif");
     QObject::connect(&b1,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&b2,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&mapper,SIGNAL(mapped(QString)),&label,SLOT(setFileName(QString)));
     label.show();
    
     return app.exec();
    

    }
    @

    When I run the executable, I get a very small window. When I expand it, I am getting a pure grey background: No pushbuttons. No gifs displayed. Nothing.

    Please help.

    Thanks,
    Qt-Newbie



  • I though you would incorporate it into existing code, my mistake:
    @
    int main(int argc, char *argv[])
    {
    QApplication app(argc, argv);

     QWidget mainWidget;
    
     QSignalMapper mapper;
     MyLabel label;
     QPushButton b1(&mainWidget);
     QPushButton b2(&mainWidget);
     mapper.setMapping(&b2,"gif2.gif");
     mapper.setMapping(&b2,"gif2.gif");
     QObject::connect(&b1,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&b2,SIGNAL(clicked()),&mapper,SLOT(map()));
     QObject::connect(&mapper,SIGNAL(mapped(QString)),&label,SLOT(setFileName(QString)));
    
     QVBoxLayout verticalLayout(&mainWidget);
     verticalLayout.addWidget(&label);
     QHBoxLayout horizontalLayout(&mainWidget);
     horizontalLayout.addWidget(&b1);
     horizontalLayout.addWidget(&b2);
     verticalLayout.addLayout(&horizontalLayout);
    
     mainWidget.show();
    
     return app.exec();
    

    }
    @


  • Moderators

    You're never calling show() on your buttons.

    While, ideally, all the widgets should be children of another parent widget with a layout, etc., the code you have is sufficient to test out the mechanics of the QSignalMapper, but you currently need to show each widget.

    Edit: Nevermind. You figured it out. :-)



  • @
    Edit: Nevermind. You figured it out. :-)
    @
    I would have included all that for the beginning, but I thought he wanted an example usage, not a complete app.


  • Moderators

    No worries. It all seems to have sorted itself out :-)



  • All,

    The example worked ! Thank you all for your notes.

    I have further questions:

    1. The worked out example indicates the ability to do the sequence:
      Push a Button --> signal/slot --> map a GIFn file --> display GIFn in mylabel

    What I would need to do is:

    a) Push a Button --> Query an interface --> Receive reply from interface --> signal/slot/map a GIF file based on interface reply --> display GIF in mylabel

    Where would I put the stub code to accomplish this ? Is there a Qt 4 solution ?

    b) Can I make system call functions in Qt 4 ? I am talking a "system()" type call to a Python 2.4 script I have already developed.

    Please reply.

    Thank you all,

    Qt-Newbie



  • [quote]
    Push a Button —> Query an interface —> Receive reply from interface —> signal/slot/map a GIF file based on interface reply —> display GIF in mylabel

    Where would I put the stub code to accomplish this ? Is there a Qt 4 solution ?
    [/quote]
    A little bit trickier, but like:
    @

    class MyMainWindow
    {
    QLabel *label;

    public slots:
    void buttonClicked(int nr)
    {
    label->setPixmap(queryInterface(nr));
    }
    };

    //and the button creation like:
    for(int i = 0; i < maxButtons; ++i)
    {
    QPushButton *b = new QPushButton(this);
    mapper.setMapping(b,i);
    connect(b,SIGNAL(clicked()),&mapper,SLOT(map()));
    myLayout->addWidget(b);
    }

    @

    Depending on how long it takes to query the interface, you might want to have a separate, slot to set the image that is being called once the interface is done.

    [quote]
    b) Can I make system call functions in Qt 4 ? I am talking a “system()” type call to a Python 2.4 script I have already developed.
    [/quote]

    Have a look at "QProcess":http://doc.qt.nokia.com/latest/qprocess.html

    DISCLAIMER: The code shown is a use case example and neither complete nor intended for direct use in an application.



  • All,

    How do I place text inside the pushbuttons ? I do not see any methods with the QPushButton class. Is it inherited ?

    Please reply.

    Thanks,
    Qt-Newbie





  • Loladiro,

    Thanks. I got the button text labels via the QAbstractButton class.

    Please explain where "queryInterface(nr)" is defined. I am a bit confused. Do I need to write a class/method for this ? Is it a wrapper ?

    Thanks,
    Qt-Newbie


  • Moderators

    Qt-newbie, please start a new thread for new topics.


  • Moderators

    I splitted it and used this title :
    Can you please recommend a textbook on Qt4



  • [quote author="qt-newbie" date="1313106592"]Loladiro,

    Thanks. I got the button text labels via the QAbstractButton class.

    Please explain where "queryInterface(nr)" is defined. I am a bit confused. Do I need to write a class/method for this ? Is it a wrapper ?

    Thanks,
    Qt-Newbie[/quote]

    Since I have no idea what kind of interface you have I just put it there to indicate where you have to query your interface.


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