keypressed and keyreleased

[J.Hilk]

@genli
I actually answered a very similar question recently, can't find it any longer or I would have linked it, but I do still have the code example:

#include <QKeyEvent>
#include <QTimer>
#include <QTime>

class mWidget : public QWidget
{
    Q_OBJECT
public:
    explicit mWidget(QWidget * parent = nullptr) : QWidget(parent){
        QObject::connect(&m_Timer, &QTimer::timeout, this, &mWidget::moveSlot);
        m_Timer.setInterval(20);
    }

protected:
    QTimer m_Timer;

    virtual void keyPressEvent(QKeyEvent *event) override{
        switch(event->key())
        {
        case Qt:: Key_Z:
        {
            if(!m_Timer.isActive()){
                m_Timer.start();
                moveSlot();
            }else
                qDebug() << "Key Z when timer running";
        }
        default: qDebug() << "Other Key" << event->key();
        }
    }

    virtual void keyReleaseEvent(QKeyEvent *event) override{
        switch(event->key())
        {
        case Qt:: Key_Z:
        {
            m_Timer.stop();
        }
        default: qDebug() << "Other Key" << event->key();
        }
    }

private slots:
    void moveSlot(){
        qDebug() << "Move" << QTime::currentTime();

}
};

IIRC the idea was to send the command regularly through serial port or something. But the base idea of this should be the same, btw no autorepeat in this case!

[jeremy_k]

@genli said in keypressed and keyreleased:

void Robot::keyReleaseEvent(QKeyEvent*keyevent)
{
if (keyevent->isAutoRepeat() == true)
{
keyevent->ignore();

Why are you ignoring the event? From the documentation:

Clearing the accept parameter indicates that the event receiver does not want the event. Unwanted events might be propagated to the parent widget.

Based on the problem description, I don't think the goal is to have something else handle the autorepeated press and release events. The widget accepting the key press needs to accept autorepeats, and use the lack of autorepeat to signal the beginning and end of the physical key press.

[genli]

@J-Hilk @KroMignon
thank you for your answer but it's still the same problem
my code with timers :
QObject::connect(&m_Timer, SIGNAL(timeout), this, SLOT(moveSlot));
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QObject::connect(&m_Timer, SIGNAL(timeout), this, SLOT(moveSlot));
m_Timer.setInterval(20);
}

MainWindow::~MainWindow()
{
delete ui;
}

void moveSlot()
{
qDebug() << "keyPressed";

}

void MainWindow::keyPressEvent(QKeyEvent*keyevent)
{
switch(keyevent->key())
{
case Qt:: Key_Z:
{
if(!m_Timer.isActive()){
m_Timer.start();
moveSlot();

    }


        }

}
}

void MainWindow::keyReleaseEvent(QKeyEvent*keyevent)
{

 switch(keyevent->key())
        {
        case Qt:: Key_Z:
        {
            m_Timer.stop();
                qDebug() << "keyReleased ";
            
            
        }

}
}

[CP71]

@genli
Hi,
I suppose you have to manage more keys, not only Z.
A possible way to do this could be:

• Having a timer always active where you could have all your managements ( like a core )
• In keyPressEvent(QKeyEvent*keyevent) store the key pressed
• In keyReleaseEvent(QKeyEvent*keyevent) clear the variable where you store key-value

Below there is an example of a body that is called from your timer
void MyObject::core()
{
...

//Moving manager
switch( keyPressed )
{
	case "Z": 
		move1();
		break;

	case "A": 
		move2();
		break;
	...

         default:
              stopMoving();
         break;
}
...

}

You must check if this solution is compatible with your project design

[genli]

@CP71 yes i have Z, S, Q, D for robot movement but i have question please is the stopMoving () function is in Keypressed ?

[CP71]

@genli
Yes,
in my idea in keyReleaseEvent you must clear keyPressed variable (for example keyPressed=""), so in the switch the program skips in default and you stop all moving.

It is clear that this logic could be improved to avoid doing the same operations

Is not key pressed but moving manager ;)

[genli]

@CP71 ok and how can i clear the keyPressed please

[CP71]

@genli

void MyObject:: keyReleaseEvent(QKeyEvent*keyevent)
{
keyPressed = ""; //No key pressed = no moving, for this I insert stopMoving in switch in default
}

void MyObject::keyPressEvent(QKeyEvent*keyevent)
{
keyPressed = keyevent->key();
}

[genli]

I changed the code but it's the same error :
void Robot::keyPressEvent(QKeyEvent*keyevent)
{
if (keyevent->key() == Qt::Key_Z)
{

   ui->forward_btn->pressed();

}
}
void Robot::keyReleaseEvent(QKeyEvent*keyevent)
{

 if (keyevent->key() == Qt::Key_Z)
 {
     ui->forward_btn->released();
   }

}
any idea please ?

[CP71]

@genli
It seems you have 2 ways to moving the robot, via keyboard and via UI (pushbutton), haven't you?

[genli]

@CP71 yes that's it

[CP71]

@genli
The idea is having one place where manage the moving.
So my idea is the same:

• having a timer always actived
• defining a enum or defines for direction
• in key event or pushbutton event store last moving selection.

Only for example:

enum Moving
{
enStop,
enForward,
enBack,
enLeft,
enRight
}

Moving moving;

void MyObject::core()
{
...
//Moving manager

switch( moving)
{
case enForward:
move1();
break;

case enBack: 
	move2();
	break;
...

     default:
          stopMoving();
     break;

}
...
}

void MyObject:: keyReleaseEvent(QKeyEventkeyevent)
{
keyPressed = enStop;
}
void MyObject::keyPressEvent(QKeyEventkeyevent)
{
if ( keyEvent->key() == "S" )
keyPressed = enForward;
else if ( keyEvent->key() == "D" )
keyPressed = enBack;
...
}

//for all 4 buttons write a code like this
void MyObject::on_forward_btn_pressed()
{
keyPressed = enForward;
]

void MyObject::on_forward_btn_relesed()
{
keyPressed = enStop;
]

The above code could have error, I write in editor and not in QTCreator.

For security the stopOperation I insert always in default.

[CP71]

@genli
Obviously, you must correctly manage two commands that are opposite ( for example left and right simultaneously ).
but switch'd already help you for this case ;)

[genli]

@CP71 the thing I can't understand is when I press Z:
The debug console shows me:
Forward
keyReleased
Forward
keyReleased
Forward
keyReleased
and when I keep pressing z and I press another button for example R or P the problem solved
The debug console shows me:
Forward
Forward
Forward
how i can press a button on the keyboard using code ?

[artwaw]

@genli create QKeyEvent and post it to the event queue https://doc.qt.io/qt-5/qcoreapplication.html#postEvent

I think the above is overly complicated though. I'd go with a set of flags, either standalone or the vector of bool, and custom signal - let's say keyboardStateChanged() or something.
In keypressed/keyreleased events you just set the flag and emit the signal.
The signal it self connected as a queued connection, so it's just processed after the control returns from the keyboard event processing, connected to the slot which in turn, sends movement commands to the remote.
Less methods, less code the way I see it, clearer approach.

EDIT: also, try do debug key events to see possible modifiers from the event. Those are platform dependent.

[CP71]

@genli
I don't know why, if you are pushing Z without release the button you should not read keyReleased.
But remember void MyObject:: keyReleaseEvent(QKeyEventkeyevent) is called for any key that is released

[genli]

@CP71 there's a way to do it with signal and slot ?

[artwaw]

@genli I think more flexible approach for you would be to go with the event filter https://doc.qt.io/qt-5/eventsandfilters.html#event-filters

[CP71]

@genli
You have several ways to do this, depend on own style, as it often happens there isn't only one way to do something.

There's a way to do it with signal and slot ?
Yes of course!
As @artwaw says you can use event filter.
I wouldn't use eventFiler, but not because is not correct, but only because it is not my style, doesn't mean that my style is the best way!

The @artwaw's tip is good, in short, think simple, less code you have less bug you will have.

My tip is the same, having one point where you manage the moving. How you send the variable, flags, and so on depends only on you and how the project is designed.

Normally in my projects, I like to have an application core manager that is independent of UI. The UI and the core communicate between them via signals.

But before going ahead, for me, you must understand because you have:
Forward
keyReleased
when wouldn't be so.