I'm repeatedly using a pair of QComboBox and QListWidget in a project. Their interaction is highly coupled - when an item is selected in the combo box, the list is filtered in some way. I'm copy pasting all the signal and slot connections between these two widgets across multiple dialog box implementation which I don't think is a good idea.
Is it possible to create a custom widget, which will hold these two widgets and will have all signal and slot connection in one place? Something like as follows:
class CustomWidget
{
QComboBox combo;
QListWidget list;
...
};
I want to use this widget as a single widget.
The usual way of doing this is to sub-class QWidget (or QFrame).
class CustomWidget: public QWidget {
Q_OBJECT
CustomWidget(QWidget *parent)
: QWidget(parent) {
combo = new QComboBox(...);
list = new QListWidget(...);
// create the appropriate layout
// add the widgets to it
setLayout(layout);
}
private:
QComboBox *combo;
QListWidget *list;
};
Handle all the interactions between the list and the combo in that custom widget (by connecting the appropriate signals to the appropriate slots, possibly defining your own slots for this).
You then expose your custom widget's behavior/API through dedicated signals and slots, possibly mimicking the ones in the list and/or the combo.
The Address book tutorial walks you through all of that, including creating a custom widget and defining signals and slots for it.
Related
I am making a gui app designer. Every time the user create a new widget, it is stored in a QWidgetList. It can be a QPushButton, a QLineEdit, whatever.
For example, let's say I have a QPushButton (index 0) and a QLineEdit (index 1).
Is it possible to access the signal clicked of WidgetList[0], or use the slot setText of WidgetList[1] ?
Or do I really have to make a QList for each type, like QList<QPushButton> and QList<QLineEdit> ?
Thanks in advance
To use the new connect syntax, you have to cast the widgets to correct types. E.g.:
QPushButton b{“clear”};
QLineEdit e;
QWidgetList widgets{&b, &e};
QObject::connect(qobject_cast<QPushButton*>(widgets[0]), &QPushButton::clicked,
qobject_cast<QLineEdit*>(widgets[1]), &QLineEdit::clear);
In a designer use case, you’ll probably be referring to signals and slots using their text signatures or QMetaMethod handles, and then there’s no need for any casting at all, since those connect methods upcast the objects to QObject anyway.
I'm new to Qt and fairly new to C++ but I need help with this issue.
I have a custom class called HybridStack and I want it to extend a QStackedWidget and a QMainWindow.
I want it to extend a QStackedWidget so that I can use as many pages as I need and I want it to extend a QMainWindow so that I could be able to make each page have it's own MenuBar with different content of menu for different page.
I want to add this custom class HybridStack to Qt Designer by
promoting it from a QStackedWidget.
Is this possible? If it is, can you brief me on how to do this? If it's not possible then what's an alternative? Most importantly, I need to use it in the Designer because I need to use qmake
You can't derive from both QStackedWidget and QMainWindow, because both of those are in turn derived from QWidget. If you did so, you'd end up with the Dreaded Diamond. You'll have to use composition instead.
Even then, I'm not sure if it would work correctly to put a QMainWindow within a QStackedWidget, since it is designed to be a top-level item (i.e. its shown directly as a window, not embedded within another QWidget). Another way of accomplishing what you want (menu bar changing when the you change tabs) would be the following:
Make your top-level item a QMainWindow
Make the central widget a custom widget derived from QStackedWidget
When the item showing in the stack widget changes, you can call QMainWindow::setMenuBar to change the menu bar. Each widget within the QStackWidget could have its own QMenuBar instance that it uses for this purpose.
Hi all,
I have some code generating a dynamically filled QMenu depending on some data (I will call it thisMenu). The QMenu thisMenu is created, taking some "main" QWidget as parent and is added to a QMenuBar within this QWidget (menuBar.addMenu(&thisMenu). Latter on, I want the user to be able of accessing thisMenu from a context menu (the user right click on some portion of the QWidget, which pops a QMenu (called contextMenu) with some actions, and the previous QMenu as a sub-menu).
If I reuse the QMenu that I first created with contextMenu.addMenu(&thisMenu) I find out that, even if contextMenu pops at the right global position, thisMenu is always translated to some other position and appearing sometimes above, sometimes under contextMenu.
I can test that this is linked to the parenting chain : thisMenu is not a child of contextMenu, if I create it a child of contextMenu, everything is fine. Is there a way of cleanly handling this case without recreating a QMenu similar to thisMenu, or changing the parent of thisMenu; i.e. reusing thisMenu in both QMenuBar and in some context menu/QMenu? In other what is the proper way of handling parenting chain for QMenu and sharing QMenu?
Thank you,
In other what is the proper way of handling parenting chain for QMenu and sharing QMenu?
You cannot share a QMenu across multiple places -- each QMenu can only exist in one place at a time. You should create separate QMenus: One for your menu bar and one for your context menu.
A simple way is to put your menu-generating code in a for-loop, to create multiple identical menus.
May I ask why you want to reuse your QMenu?
I can test that this is linked to the parenting chain : thisMenu is not a child of contextMenu
Yes, that is described in the documentation. When you add one QMenu to another, the parent doesn't change: http://qt-project.org/doc/qt-5/QMenu.html#addMenu
if I create it a child of contextMenu, everything is fine.
The position of a widget is always painted in a position relative to its parent. (Remember: A QMenu is a QWidget)
Following JKSH's answer, I decided to use a function to duplicate QMenu, without duplicating the QAction in it (they are not inheriting QWidget), hence conserving all established connections :
void duplicateMenu(QMenu* dst, QMenu& origin)
{
QMenu* sub = dst->addMenu(origin.title());
QList<QAction*> actions=origin.actions();
for(QList<QAction*>::iterator it=actions.begin(); it!=actions.end(); it++)
{
QMenu* itMenu = (*it)->menu();
if(itMenu!=NULL)
duplicateMenu(sub, *itMenu);
else
sub->addAction(*it);
}
}
i have just one QMainWindow with mainwindow.ui where i have tables, buttons etc...
From one button i want to dynamically create widget and set an evenFilter on it.
QWidget dialog = new QWidget();
dialog->installEventFilter(this);
When i compile program it says that QObject::installEventFilter(): Cannot filter events for objects in a different thread.
How can i add this widget to thread with other Qobjects or what is best solution to this problem?
You should not create gui widgets from non gui threads.
Create subclass of QWidget and install there eventFilter, put inside signals to return result back.
And than send signal from your thread to main thread slot to create this QWidget dialog = new MyWidget() and use as you want.
I have a QGraphicsItem that has text on it. I want this text to be editable, so that if the user double-clicks it, it will enter an edit mode. It seems like the easiest way to do this would be to change the text into a QLineEdit and let the user click away the focus or press enter when they're done.
How can I add a QLineEdit to a QGraphicsItem? I have subclassed the QGraphicsItem so I have access to its internals.
To add any QWidget based object to a QGraphicsScene, a QGraphicsProxyWidget is required.
When you call the function addWidget on QGraphicsScene, it embeds the widget in a QGraphicsProxyWidget and returns that QGraphicsProxyWidget back to the caller.
The QGraphicsProxyWidget forwards events to its widget and handles conversion between the different coordinate systems.
Now that you're looking at using a QLineEdit in the QGraphicsScene, you need to decide if you want to add it directly:
QGraphicsScene* pScene = new QGraphicsScene;
QLineEdit* pLineEdit = new QLineEdit("Some Text");
// add the widget - internally, the QGraphicsProxyWidget is created and returned
QGraphicsProxyWidget* pProxyWidget = pScene->AddWidget(pLineEdit);
Or just add it to your current QGraphicsItem.
Here, you can either add it as a child of the QGraphicsItem:
MyQGraphicsItem* pMyItem = new MyQGraphicsItem;
QGraphicsProxyWidget* pMyProxy = new QGraphicsProxyWidget(pMyItem); // the proxy's parent is pMyItem
pMyProxy->setWidget(pLineEdit); // adding the QWidget based object to the proxy
Or you could add the QGraphicsProxyWidget as a member of your class and call its relevant functions, but adding it as a child is probably much simpler.
QGraphicsTextItem::setTextInteractionFlags (Qt::TextInteractionFlags flags)
API can be used. But you need to create QGraphicsTextItem inside it.
Please check following link for details: Implementation details
You need to create a proxy widget by extending QGraphicsProxyWidget in the case you need some specific behavior or just use a QGraphicsProxyWidget. Take a look at the "Embedded Dialogs" example in your Qt SDK and the QGraphicsProxyWidget documentation. It has been there for a long time so it should be for your version. I hope this helps.