How to emulate a QPushButton click in Qt with QEvents

Question

I have a custom input device on and embedded system, and have to translate the input to proper events in Qt. In my current view I have a QListView and some QPushButtons. I use the following code in my widget.

QKeyEvent * e = NULL;
if (cmd.up.value)
    e = new QKeyEvent(QEvent::KeyPress, Qt::Key_Up, 0, 0);
else if (cmd.down.value)
    e = new QKeyEvent(QEvent::KeyPress, Qt::Key_Down, 0, 0);
else if (cmd.left.value)
    e = new QKeyEvent(QEvent::KeyPress, Qt::Key_Left, 0, 0);
else if (cmd.right.value)
    e = new QKeyEvent(QEvent::KeyPress, Qt::Key_Right, 0, 0);
else if (cmd.ok.value)
    e = new QKeyEvent(QEvent::KeyPress, Qt::Key_Space, 0, 0);

if (e)
    QApplication::postEvent(this->focusWidget(), e);

I can move up/down/right/left between list and buttons, but I can't click the buttons. I've tried using Qt::Key_Enter and Qt::Key_Return as well, but neither works.

If run the application on my pc, hitting space or the left mouse button on my keyboard gives a button click. That indicates that somewhere, the event is changed to something the pushbutton likes better than getting a Qt::Key_Space directly, right?

Anyone got an idea for how I can solve this nicely? I can check which (if any) button has focus and click it manually, but that is not very elegant coding...

Have you tried using a QMouseEvent to send a mouse click to the button? — Chris, Jan 02 '12 at 15:54
Is there some problem with my answer? Please tell if there is, I might be able to help more. — 0xbaadf00d, Jan 05 '12 at 05:06

score 1 · Answer 1 · answered Jan 03 '12 at 12:13

1

[QT_FOLDER]/src/gui/widgets/qpushbutton.cpp : line 459

QPushButton accepts Key_Enter and Key_Return if defaultButton is set to true. I don't know where the space button is changed to something different, but here's my fix:

Create a class MyPushButton and reimplement keyPressEvent. Then just handle Enter and Return with a call to click

It should be very simple.

Edit:

Or if you want fancy, create your own custom events for your device and handle those events in your derived classes exactly as you wish.

answered Jan 03 '12 at 12:13

0xbaadf00d

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Thanks for the reply. I've tried both approaches and ended up somewhere in between. The widgets that need it input implement an event handler that translate the custom input to the QEvents wanted by the children in that widget. The buttons I used were set to autoDefault, so from the source code it seems that should have worked too. Anyway - working with a combination of your suggestions - custom input handler calling click() on active button. Thanks. – anr78 Jan 10 '12 at 07:08

score 1 · Accepted Answer · answered Jan 13 '12 at 11:03

The solution to this was actually quite simple. A QPushButton isn't clicked on KeyPress, but on KeyRelease. New code below.

if (cmd.up.value)
{
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyPress, Qt::Key_Up, 0, 0));
}
else if (cmd.down.value)
{
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyPress, Qt::Key_Down, 0, 0));
}
else if (cmd.left.value)
{
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyPress, Qt::Key_Left, 0, 0));
}
else if (cmd.right.value)
{
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyPress, Qt::Key_Right, 0, 0));
}
else if (cmd.ok.value) 
{
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyPress, Qt::Key_Space, 0, 0));
    QApplication::postEvent(this->focusWidget, 
                            new QKeyEvent(QEvent::KeyRelease, Qt::Key_Space, 0, 0));
}

How to emulate a QPushButton click in Qt with QEvents

2 Answers2