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Thread: How to use QSignalMapper for a list of QAction items

  1. #1
    Join Date
    Feb 2014
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    Qt products
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    Platforms
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    Default How to use QSignalMapper for a list of QAction items

    I am developing a code snippet to perform similar, not identical actions when I click on the sub menu item list. Please check the attached snapshot. QSignalMapper is the best solution to connect multiple signals to the same slot.
    snap1.jpg

    But I am not able to exactly place, which signal is to be called for which slot. I have read a lot of theory about QSignalMapper,
    Qt Code:
    1. http://qt-project.org/doc/qt-4.8/qsignalmapper.html
    2. http://doc.qt.digia.com/qq/qq10-signalmapper.html#thesignalmapperapproach
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    even implemented their codes. Unlike the mentioned sample programs, my QAction objects apparently cannot be defined like we define elements inside an array, coz their names were auto-generated by the design window.
    snap2.jpg

    I am not able to understand, what should I place as SIGNAL here, and when should I use the setMapping function? If I use setMapping function, which parameters should I implement? I am simply not getting the concept thorough, not knowing what to do, whom to ask and making the mistake in my code here. Can you please advise me what I am doing wrong? I checked this for reference coz he had similar issue:
    Qt Code:
    1. http://stackoverflow.com/questions/14151443/how-to-pass-a-qstring-to-a-qt-slot-from-a-qmenu-via-qsignalmapper-or-otherwise/14157471#14157471
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    Here's the code which requires 4-5 steps, which I am not getting, to be added for making it work:

    mainwindow.h
    Qt Code:
    1. #ifndef MAINWINDOW_H
    2. #define MAINWINDOW_H
    3.  
    4. #include <QMainWindow>
    5. #include <QDebug>
    6. #include <QSignalMapper>
    7.  
    8. namespace Ui {
    9. class MainWindow;
    10. }
    11.  
    12. class MainWindow : public QMainWindow
    13. {
    14. Q_OBJECT
    15.  
    16. public:
    17. explicit MainWindow(QWidget *parent = 0);
    18. ~MainWindow();
    19.  
    20.  
    21. private:
    22. Ui::MainWindow *ui;
    23. void createActions();
    24.  
    25. private slots:
    26. void interval();
    27. void help();
    28. int setAreaThreshold();
    29.  
    30. };
    31.  
    32. #endif // MAINWINDOW_H
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    mainwindow.cpp
    Qt Code:
    1. #include "mainwindow.h"
    2. #include "ui_mainwindow.h"
    3. //#include "intervaldialog.h"
    4. //#include "help.h"
    5.  
    6. int i =25;
    7. MainWindow::MainWindow(QWidget *parent) :
    8. QMainWindow(parent),
    9. ui(new Ui::MainWindow)
    10. {
    11. ui->setupUi(this);
    12. createActions();
    13. }
    14.  
    15. MainWindow::~MainWindow()
    16. {
    17. delete ui;
    18. }
    19.  
    20. void MainWindow::createActions()
    21. {
    22. ui->actionInterval->setStatusTip(tr("Set the interval for capturing delta & reference images"));
    23. connect(ui->actionInterval, SIGNAL(triggered()), this, SLOT(interval()));
    24.  
    25. QSignalMapper *pSignalMapper = new QSignalMapper(this);
    26. connect(ui->menuArea_Threshold, SIGNAL(triggered(QAction*)), this, SLOT(setAreaThreshold()));
    27.  
    28.  
    29. ui->menuHelp->setStatusTip(tr("help "));
    30. }
    31.  
    32. void MainWindow::interval()
    33. {
    34. qDebug()<<"inside interval qdialog";
    35. }
    36.  
    37. int MainWindow::setAreaThreshold()
    38. {
    39. qDebug()<<"setting area threshold";
    40.  
    41. // qDebug()<<str;
    42. // int i = str.toInt();
    43. // qDebug()<<i;
    44. // QString areaThresholdString;
    45. // areaThresholdString = ui->action25_sec->text();
    46. // switch (areaThresholdString) {
    47. // case 25:
    48. // qDebug()<<"25";
    49. // break;
    50. // default:
    51. // qDebug()<<"default";
    52. // break;
    53. // }
    54.  
    55. return 0;
    56. }
    57.  
    58. void MainWindow::help()
    59. {
    60. Help help;
    61. help.exec();
    62. }
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    main.cpp
    Qt Code:
    1. #include "mainwindow.h"
    2. #include <QApplication>
    3.  
    4. int main(int argc, char *argv[])
    5. {
    6. QApplication a(argc, argv);
    7. MainWindow w;
    8. w.show();
    9.  
    10. return a.exec();
    11. }
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  2. #2
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    Default Re: How to use QSignalMapper for a list of QAction items

    Something like:
    Qt Code:
    1. QSignalMapper *pSignalMapper = new QSignalMapper(this);
    2. connect(pSignalMapper, SIGNAL(mapped(int)), SLOT(setAreaThreshold(int)));
    3. connect(ui->action25, SIGNAL(triggered()), pSignalMapper, SLOT(map()));
    4. connect(ui->action50, SIGNAL(triggered()), pSignalMapper, SLOT(map()));
    5. connect(ui->action100, SIGNAL(triggered()), pSignalMapper, SLOT(map()));
    6. connect(ui->action150, SIGNAL(triggered()), pSignalMapper, SLOT(map()));
    7. connect(ui->action200, SIGNAL(triggered()), pSignalMapper, SLOT(map()));
    8. pSignalMapper->setMapping(ui->action25, 25);
    9. pSignalMapper->setMapping(ui->action50, 50);
    10. pSignalMapper->setMapping(ui->action100, 100);
    11. pSignalMapper->setMapping(ui->action150, 150);
    12. pSignalMapper->setMapping(ui->action200, 200);
    13.  
    14. // and a slot
    15. void setAreaThreshold(int value) {
    16.  
    17. }
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  3. The following user says thank you to ChrisW67 for this useful post:

    Sai Kamat (4th March 2014)

  4. #3
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    Default Re: How to use QSignalMapper for a list of QAction items

    Or setting the value as the action's custom data and retrieving it in the slot

    Qt Code:
    1. ui->action25->setData(25);
    2. .....
    3. connect(ui->menuArea_Threshold, SIGNAL(triggered(QAction*)), this, SLOT(setAreaThreshold(QAction*)));
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    Qt Code:
    1. setAreaThreshold(QAction *action)
    2. {
    3. int value = action->data().toInt();
    4. }
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    Cheers,
    _

  5. The following user says thank you to anda_skoa for this useful post:

    ChrisW67 (4th March 2014)

  6. #4
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    Default Re: How to use QSignalMapper for a list of QAction items

    Thanks anda_skoa, must remember that variation.

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