I am using Qt but have run into a problem.
I want to register when the mouse is pressed and released on a QTableWidget. There are signals only for pressed, not released. Therefore I use mousePressEvent and mouseReleaseEvent instead.
MyWidget.h
protected:
void mousePressEvent(QMouseEvent * event);
void mouseReleaseEvent(QMouseEvent * event);
MyWidget.cpp
void MyWidget::mousePressEvent(QMouseEvent *event)
{
qDebug() << "Pressed";
}
void MyWidget::mouseReleaseEvent(QMouseEvent *event)
{
qDebug() << "Released";
}
It prints "Released" when the left, right or middle mouse button is released over the table. However, it prints "Pressed" only when the right or middle button is pressed.
What could be wrong? How can I register when the left button is pressed?
The cell widget probably consumes the mousePressEvent on the left mouse button, so you (the parent widget) are not receiving it.
In the documentation of QMouseEvent, it is said that:
A mouse event contains a special accept flag that indicates whether the receiver wants the event. You should call ignore() if the mouse event is not handled by your widget. A mouse event is propagated up the parent widget chain until a widget accepts it with accept(), or an event filter consumes it.
Because of that, we can suppose that probably the events you mentioned are consumed by some other actors.
It would help knowing who are those actors.
I found the solution (with help from the other answers):
There was a QFrame on top of the widget that consumed the event. I didn't think of that since it worked for the other buttons. It was solved by:
ui->frame->setAttribute(Qt::WA_TransparentForMouseEvents, true);
Related
I've overrode the eventFilter method of the MainWindow of the application
bool MainWindow::eventFilter(QObject *obj, QEvent *event){
if(event->type()== QEvent::MouseButtonRelease){
cout<<"CATCH"<<endl;
}
return QObject::eventFilter(obj,event);
}
I can get all events thrown by QWidgets except events arose by QPushButton and Widgets that implement the click event,I mean if I click on the background I can get the release event,if i click
on a QLabel or a QWidget Container i still get the event, but I can't get mouse events from QPushButton, QCalendar, GroupBox etc...
I've tried to promote (I'm using QtCreator) the QPushButton overriding both the methods
void mousePressEvent(QMouseEvent* event) override;
void mouseReleaseEvent(QMouseEvent* event) override;
But even this does not work because these methods are not called when clicking on the QPushButton.
So I've overrode the filter method of the button and I can catch only graphic events like PaletteChangeEvent or RepaintingEvent.
What am I doing wrong?
You have to install an EventFilter in your buttons and QWidgets to receive the events that are sent to those objects before them.
By doing that you can define a method that receive all the events that are sent to those objects and you can catch the ones you want.
Read this to see an example: Event Filters
I want hide a QWidget when mouse clicks out of that widget just like it have a popup flag:
auto widget = new QWidget(this);
widget->setWindowFlag(Qt::Popup); // this widget will hide, when mouse click out of that widget.
For some reason, I can't set these flags and must implement some thing myself which behaves like this.
Or can I get a mouse event out of that widget?
Solution:
As I said, I can't use Qt flags and have to implement the similar behavior myself.My solution is installEventFilter to QApplication, in the override method eventFilter,I filter the QMouseEvent and send a signal.
Yes, you can get a mouse event out of the widget.
Make a custom widget and reimplement mousePressEvent, which will catch the last click (the ouside-the-widget click that hides the "popup"). But be careful to add the call to QWidget::mousePressEvent(event) in the end, otherwise the last click will be lost and your widget will remain onscreen.
CustomWidget::CutomWidget(QWidget *parent) : QWidget(parent)
{
setWindowFlags(Qt::Popup);
}
void CustomWidget::mousePressEvent(QMouseEvent *event)
{
if (!this->underMouse()) {
//if the click is not on the widget, i.e. if it's the click that hides it,
// you caught it, do what you want to do here.
}
QWidget::mousePressEvent(event);
}
Hope it helps.
I would simply like to catch the mouseRelease event when a user drags an item from a QTableView and releases the left button.
I want to highlight possible dropping zones in my app, like changing the background of a widget.
I start by detecting the drag-start by re-implementing:
void LibraryTableView::startDrag( Qt::DropActions supportedActions )
{
m_dragReleased = false;
emit dragStart();
QTableView::startDrag(supportedActions);
}
and emitting my own signal.
Now that the dropzone has changed, I need to catch the release event to redraw the dropzone as before whether the drag and drop succeded or not !
I tried different models, reimplementing the 4 mouse events and eventFilter, but the Mouse Release Event is never catched.
Here is my code:
void LibraryTableView::mouseDoubleClickEvent( QMouseEvent* event )
{
QTableView::mouseDoubleClickEvent(event);
}
void LibraryTableView::mouseMoveEvent( QMouseEvent* event )
{
qDebug() << "move";
QTableView::mouseMoveEvent(event);
}
void LibraryTableView::mousePressEvent( QMouseEvent* event )
{
qDebug() << "press";
QTableView::mousePressEvent(event);
}
void LibraryTableView::mouseReleaseEvent( QMouseEvent* event )
{
qDebug() << "real"; // Never called when drag ends ...
QTableView::mouseReleaseEvent(event);
}
So, it is a bug ?
If you know a trick, it would help me a lot.
Thanks !
Edit: I cannot reimplement dropEvent for every widget in my application, if the user drags and drop an element in another application, I still want to catch the release event ...
As said above it's been 3 years but thank to the last answer I found an even easier solution for this problem.
void LibraryTableView::startDrag( Qt::DropActions supportedActions )
{
m_dragReleased = false;
emit dragStart();
QTableView::startDrag(supportedActions);
//CODE HERE WILL BE EXECUTED ONLY WHEN THE MOUSE BUTTON HAS
//BEEN RELEASED SO YOU CAN DO THE FOLLOWING
emit dragStop();
}
Three years since this question was asked and this Qt problem still exists in Qt 5.4. Lately I had the same problem: Drops outside the application and no MouseReleaseEvent. The solution is simple and not really a trick:
The mousePressEvent, which starts the drag&drop looks like this (simplified):
void DragNDropListView::mousePressEvent(QMouseEvent *event){
....
QDrag *drag = new QDrag(this);
QMimeData *mimeData = new QMimeData;
mimeData->setData("application/x-xxxxxx", QByteArray());
drag->setMimeData(mimeData);
drag->exec();
// The d&d ended here. Inside the widget where the drag
// started, a mouseReleaseEvent would have been fired.
// Outside this widget not.
// drag->mimeData() is here still available.
}
}
}
The trick is simple: drag->exec() starts its own event loop, which is exited when the mouse button is released. The mouse position after drag->exec(); can be determined with QCursor.
For QTableView you have to reimplement three function for dnd support:
void dragEnterEvent ( QDragEnterEvent * event ) - in this function the mouse enters the widget
void QAbstractItemView::dragMoveEvent ( QDragMoveEvent * event ) - in this function you can update your drop zone highlighting
void QAbstractItemView::dropEvent ( QDropEvent * event ) - in this function you decide whether to accept the event
I encountered a similar issue and was not happy to find out that the MouseReleaseEvent was not getting fired at the end of a drag.
I just used the DragLeaveEvent and toggled my variables off, as I would have done in the MouseReleaseEvent. If user dragged off the app, and then back on, those previously toggled off variables would get re-enabled in the DragMoveEvent (assuming it is accepted).
That was my trick, at least. Hope it helps.
i have a class implemented from QGraphicsItem, called Node.
i have a rectangle shaped "Node" and i can do something when user clicked on it
i use mousePress and mouseRelease events.
but i want to be notified when user clicked "out of" the rectangle shape.
i tried to implement these functions:
Qt Code:
void Node::focusInEvent ( QFocusEvent * event){
cout<<"in"<<endl;
update();
QGraphicsItem::focusInEvent(event);
}
void Node::focusOutEvent ( QFocusEvent * event ){
cout<<"out"<<endl;
update();
QGraphicsItem::focusOutEvent(event);
}
void Node::hoverEnterEvent(QGraphicsSceneHoverEvent *event){
cout<<"out"<<endl;
}
these do not reacts if i click in or out of rectangle.
should i set a logic on my own for example getting the mouse position and control if it is out of rectangle?
or is there a built in method?
or how can a "Node" object know if other Node object is clicked?
also i wonder, googled but could not found that when does focusinevent and focusoutevent triggered? I guess focusOutEvent must work when i had clicked in the item, then out of the item, am i wrong?
thanks for idea.
You need to do the following when you construct your nodes:
setFlag( QGraphicsItem::ItemIsFocusable );
setAcceptHoverEvents( true );
The first line makes your item actually capable of receiving focus, and the latter makes it so your item is notified of mouse events.
Have you called setFlags method of your graphics item with QGraphicsItem::ItemIsSelectable or QGraphicsItem::ItemIsMovable ?
According to QT doc.
By default, no flags are enabled.
In my program, I'd like to have mouseMoveEvent(QMouseEvent* event) called whenever the mouse moves (even when it's over another window).
Right now, in my mainwindow.cpp file, I have:
void MainWindow::mouseMoveEvent(QMouseEvent* event) {
qDebug() << QString::number(event->pos().x());
qDebug() << QString::number(event->pos().y());
}
But this seems to only be called when I click and drag the mouse while over the window of the program itself. I've tried calling
setMouseTracking(true);
in MainWindow's constructor, but this doesn't seem to do anything differently (mouseMoveEvent still is only called when I hold a mouse button down, regardless of where it is). What's the easiest way to track the mouse position globally?
You can use an event filter on the application.
Define and implement bool MainWindow::eventFilter(QObject*, QEvent*). For example
bool MainWindow::eventFilter(QObject *obj, QEvent *event)
{
if (event->type() == QEvent::MouseMove)
{
QMouseEvent *mouseEvent = static_cast<QMouseEvent*>(event);
statusBar()->showMessage(QString("Mouse move (%1,%2)").arg(mouseEvent->pos().x()).arg(mouseEvent->pos().y()));
}
return false;
}
Install the event filter when the MainWindows is constructed (or somewhere else). For example
MainWindow::MainWindow(...)
{
...
qApp->installEventFilter(this);
...
}
I had the same problem, further exacerbated by the fact that I was trying to call this->update() to repaint the window on a mouse move and nothing would happen.
You can avoid having to create the event filter by calling setMouseTracking(true) as #Kyberias noted. However, this must be done on the viewport, not your main window itself. (Same goes for update).
So in your constructor you can add a line this->viewport()->setMouseTracking(true) and then override mouseMoveEvent rather than creating this filter and installing it.