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Thread: Key Press Event Handling

  1. #1
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    Default Key Press Event Handling

    I know, there is more thread about that in this forum. I looked all of them, but still i cant work it.

    Vista Business
    Qt SDK 2010.05
    Qt Creator 2.0.1

    I'm just trying to get which key is pressed.

    mainwindow.h
    Qt Code:
    1. #ifndef MAINWINDOW_H
    2. #define MAINWINDOW_H
    3.  
    4. #include "ui_mainwindow.h"
    5.  
    6. class MainWindow : public QMainWindow, private Ui::MainWindow
    7. {
    8. Q_OBJECT
    9. private:
    10. Ui::MainWindow *gui;
    11.  
    12. public:
    13. explicit MainWindow(QWidget *parent = 0);
    14.  
    15. protected:
    16. bool keypres(QKeyEvent *keyevent);
    17.  
    18. };
    19.  
    20. #endif // MAINWINDOW_H
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    mainwindow.cpp

    Qt Code:
    1. #include "mainwindow.h"
    2. #include <QKeyEvent>
    3. #include <QDebug>
    4.  
    5. MainWindow::MainWindow(QWidget *parent) :
    6. QMainWindow(parent),gui(new Ui::MainWindow){
    7. gui->setupUi(this);
    8.  
    9. gui->textEdit->installEventFilter(this);
    10.  
    11. }
    12.  
    13. bool MainWindow::keypres(QKeyEvent *keyevent)
    14. {
    15. if (keyevent->key()==Qt::Key_W)
    16. {
    17. qDebug() << "hi";
    18. }
    19. }
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    main.cpp

    Qt Code:
    1. #include <QtGui/QApplication>
    2. #include "mainwindow.h"
    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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    I just want to control keys and key events.
    Regards.

  2. #2
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  3. #3
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    Default Re: Key Press Event Handling

    You need to set a focusPolicy

  4. #4
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    Default Re: Key Press Event Handling

    Your event handler signature is wrong.
    The documentation for QObject::installEventFilter() has an example exactly for key press events.
    Why not start there?
    http://doc.qt.nokia.com/latest/qobje...allEventFilter
    Last edited by high_flyer; 22nd March 2011 at 16:16. Reason: typo
    ==========================signature=============== ==================
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    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.

  5. #5
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    Default Re: Key Press Event Handling

    Well then.
    @pan : i added focus policy
    and done somethings but thats have no effect.

    i made it with QDialog base class. But with QMainWindows its not working. I'm tired.
    I just open Qt Creator and create gui application, which is using QMainWindow base class.

    mainwindows.cpp
    Qt Code:
    1. #include "mainwindow.h"
    2. #include <QDebug>
    3.  
    4. MainWindow::MainWindow(QWidget *parent) :
    5. QMainWindow(parent), ui(new Ui::MainWindow)
    6. {
    7. ui->setupUi(this);
    8. this->setWindowFlags(Qt::Dialog);
    9. this->setFocusPolicy(Qt::NoFocus);
    10. ui->textEdit->setFocusPolicy(Qt::StrongFocus);
    11. ui->textEdit->installEventFilter(this);
    12. }
    13.  
    14. bool MainWindow::catch_event(QObject *obj, QEvent *event)
    15. {
    16. if (obj == ui->textEdit && event->type()==QEvent::KeyPress)
    17. {
    18. QKeyEvent *keyevent = static_cast<QKeyEvent*>(event);
    19. qDebug() << "key event";
    20. return QObject::eventFilter(obj,event);
    21. }
    22. return QObject::eventFilter(obj,event);
    23. }
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    Problem is not solved but i'm tired about 2 days. I will do with QDialog class.

    Thanks all...

  6. #6
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    Default Re: Key Press Event Handling

    Problem is not solved but i'm tired about 2 days.
    I told you what the problem is!
    And I gave a link to almost exactly the code you need, you only need to copy paste and introduce the changes in the handler to do the filtering based on the rules you need it.
    So what is the problem?


    heh... you really should read your own signature and apply some though on it...
    ==========================signature=============== ==================
    S.O.L.I.D principles (use them!):
    https://en.wikipedia.org/wiki/SOLID_...iented_design)

    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.

  7. #7
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    Default Re: Key Press Event Handling

    Ok. Punch me
    Bro its really not working. You think, i make joke ?
    Try if you didnt believe ok.
    Thanks so.

    I'm missing something' s.. But i cant find it yet.

  8. #8
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    Default Re: Key Press Event Handling


    The event filter filterObj receives events via its eventFilter() function.
    not 'catch_event'.

    all you had to do is COPY PASTE the example!!

    Qt Code:
    1. //change the class name to your
    2. bool KeyPressEater::eventFilter(QObject *obj, QEvent *event)
    3. {
    4. if (event->type() == QEvent::KeyPress) {
    5. //and here put your own logic!!
    6. QKeyEvent *keyEvent = static_cast<QKeyEvent *>(event);
    7. qDebug("Ate key press %d", keyEvent->key());
    8. return true;
    9. } else {
    10. // standard event processing
    11. return QObject::eventFilter(obj, event);
    12. }
    13. }
    To copy to clipboard, switch view to plain text mode 
    ==========================signature=============== ==================
    S.O.L.I.D principles (use them!):
    https://en.wikipedia.org/wiki/SOLID_...iented_design)

    Do you write clean code? - if you are TDD'ing then maybe, if not, your not writing clean code.

  9. #9
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    Default Re: Key Press Event Handling

    Well, show me a corner. I will cry at there...

    Qt Code:
    1. this->textEdit->installEventFilter(this);
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    I find where i missed up.
    My goal is make a terminal program like putty.
    Thanks.

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