When I add a pop up menu in Qt as follows:
QMenu menu(widget);
menu.addAction("AAA");
menu.exec(eventPress->globalPos());
How do I control "AAA" action events. e.g. do something when "AAA" is clicked.
You can overloaded addAction.
From Qt assistant
This convenience function creates a new action with the text text and
an optional shortcut shortcut. The action's triggered() signal is
connected to the receiver's member slot. The function adds the newly
created action to the menu's list of actions and returns it.
MyClass::Popup()
{
QMenu menu(widget);
menu.addAction("AAA", this, SLOT(burnCase()));
menu.exec(eventPress->globalPos());
}
// This is your slot
MyClass::burnCase()
{
}
Related
I am using QT 4.8 and C++ and I need a default push button which will be pressed when some text are input in a lineEdit and ENTER key is pressed.
According to the QT document for the property "default" of pushbutton.
the behavior is only for dialogs.
"The default button behavior is provided only in dialogs. Buttons can always be clicked from the keyboard by pressing Spacebar when the button has focus."
How can I have this behavior for a widget, which is a container for all my GUI components.
Thanks.
You can connect the signal QLineEdit::returnPressed() to the slot QAbstractButton::click().
Method 1
from the Designer you simply can:
Right-click on lineEdit
Select "Go to slot..."
Choose returnPressed():
Press ok
In the code view you will see the slot connected to the chosen signal
You can simply call the click() slot of a button you need:
Method 2
You can manually connect signal of any lineEdit to a slot of any pushButton:
In Qt 4 syntax:
connect(ui->lineEdit, SIGNAL(returnPressed()),
ui->anyButton, SLOT(click()));
In new Qt 5 syntax:
connect(ui->lineEdit, &QLineEdit::returnPressed,
ui->anyButton, &QPushButton::click);
I have a QAction in QMenu. When QAction is triggered() I would like to know which button did it.
connect(YourAction, SIGNAL(triggered()), this, SLOT(actionclicked()));
void MainWindow::actionclicked(QMouseEvent *e)
{
if (e->buttons() == Qt::RightButton)
}
I can't do something like this because triggered() does not have such argument.
As #mvidelgauz noticed, QAction is abstracted from input devices which may triggered the action. Nevertheless, if the action is used in your GUI, it has one or more associated widgets: tool buttons in a toolbar, entries in menu bar and so on. These widgets act like any other widgets, so they receive events which may be filtered with the use of installEventFilter and eventFilter. These two methods are inherited from QObject, so they are present in almost any Qt class. For example, let's create an application with QMainWindow and QAction called actionTest. Then let's turn the main window itself into an action filter for actionTest's associated widgets by overriding main window's eventFilter method:
bool eventFilter(QObject *obj, QEvent *ev) {
//Catch only mouse press events.
if(ev->type() == QEvent::MouseButtonPress) {
// Cast general event to mouse event.
QMouseEvent *mev = static_cast<QMouseEvent*>(ev);
// Show which button was clicked.
if(mev->button() == Qt::LeftButton) {
qDebug() << "Left button!";
}
if(mev->button() == Qt::RightButton) {
qDebug() << "Right button!";
}
}
// In this example we just showed the clicked button. Pass the event
// for further processing to make QAction slots work.
return QMainWindow::eventFilter(obj, ev);
}
Then we need to install event filter object for all watched objects, which are widgets in our case. Let's do it in main window constructor:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
for(auto wgtPtr : ui->actionTest->associatedWidgets()) {
wgtPtr->installEventFilter(this);
}
}
Finally, add a slot for triggered() signal handling:
void on_actionTest_triggered() {
qDebug() << "Action triggered!";
}
Now if you click the action menu entry with left mouse button, it will print
Left button!
Action triggered!
while for right mouse button the result will be
Right button!
Action triggered!
Note that widget event filtering is always performed before triggered() signal emission.
The above code is just an example, and MainWindow class is not the best place to host eventFilter method. In real code you may either:
Create dedicated QObject subclass(es) for QAction widgets event filtering.
Subclass QAction and override it's eventFilter method. In this case you may just save the result of QMouseEvent::button() in the QAction subclass object and later use it in triggered() signal handler. There is a minor inconvenience that Qt creator (at least up to v3.2.1) does not allow you to "promote" QActions in it's form designer, so you'll need to add actions to menus manually in window constructor.
Subclass QMenu, QToolBar, etc.., and make them action filters? I don't know how can it be better than two former variants.
See also documentation about Qt event system.
Let's clarify case 2. Assume the class inherited from QAction is called MyAction. In order to make it work you need to install MyAction objects as filters for themselves (their widgets, to be more specific). You need to do it after widgets were created, so installing filter in MyAction constructor may be premature and lead to crashes. Better place for filter installation is a constructor of a class which owns MyAction object. Typically it's a widget or window class. So just add
for(auto wgtPtr : ui->myActionObject->associatedWidgets()) {
wgtPtr->installEventFilter(ui->myActionObject);
}
to your window constructor after ui->setupUi(this) call. This code is like in the above example, but we use ui->myActionObject instead of this object as filter.
triggered() cannot have this argument by design because it by itself is not necessarily result of a mouse event:
This signal is emitted when an action is activated by the user; for example, when the user clicks a menu option, toolbar button, or presses an action's shortcut key combination, or when trigger() was called
You need to connect to mouse events if you need QMouseEvent as parameter. In fact Qt itself emits triggered() when (but not only as I highlighted in doc quote) framework receives mouse event from menu. So it looks like you'll need to do a similar thing in your code and add your own logic.
P.S. This discussion might be interesting for you
I have a QMenu and actions added to it. Works fine. Assume it does have menu called "Paste here" in it.
So now I have 3 buttons, I assign this same menu to three buttons:
btnNum1->setMenu(MyMenu);
btnNum2->setMenu(MyMenu);
btnNum3->setMenu(MyMenu);
Now in the triggered slot, when I do:
qDebug() << QObject::sender();
I get the QAction which is the submenu item, I want to know which button invoked the menu which then user clicked on a menu item and triggered the slot. I need to know is it menu loaded in btnNum1 or btnNum2 or btnNum3.
Is it even possible?
Following the answer In Qt 4.7, how can a pop-up menu be added to a QToolbar button? I can create menus on the fly, but how can I connect these menus in a way that I recognize which menu was used?
If I create these menus in a loop, I have to connect all of them to same slot
For example when I have a button and I create menus for it:
button
-menu 1
-menu 2
Using code similar to this
int r=0;
while (r<2)
{
QAction *action = new QAction("menu " + QString::number(r), this);
Menus->addAction(action);
// here I could use connect in order to connect this menu to a certain slot
// but that would make all of them trigger the same function
r++;
}
ui->Button->setMenu(Menus);
How do I recognize if menu I activated was menu 1 or menu 2? Is it possible to create a slot which has pointer to sender object so that I can for example, read the text?
I am developing a project using Qt4 and I have run into a slight issue.
I am creating a modal window from the main window. I want this to disable the toolbar at the top.
I have a menu item that spawns the modal from the menu. What I want is that when the modal is spawned that menus is disabled. I have tried using the setEnabled(false) function but that doesn't reset it.
Here is the code:
void Main_Screen::Create_ViPro()
{
std::auto_ptr<ViPro_Dialog> modal(new ViPro_Dialog(this));
modal->show();
modal->exec();
}
So It is just a simple class that is triggered when a menu item is selected. I feel that the problem stems from the fact that i'm setting the parent to the main screen, however I don't know how to create a modal without a parent(it doesn't make sense to do that). Is there a way to disable the parents toolbar from the child? The only thing I have seen so far is _fileMenu->setEnabled(false);
That works as long as I don't create the modal, but as soon as that is spawned, the menu works again. I'm totally lost.
Thanks in advance
Edit as Patrice
Here is the constructor
Main_Screen::Main_Screen(QWidget* parent /*= NULL*/)
: QMainWindow(parent),
_newProj(new QAction(tr("New &ViPro"), this)),
_fileMenu(menuBar()->addMenu(tr("&File")))
{
//create slot for creating a new project
connect(_newProj.get(), SIGNAL(triggered()), this, SLOT(Create_ViPro()));
_fileMenu->addAction(_newProj.get());
//if i do this then setEnabled(false) works perfectly and i can't access the menu
Create_ViPro()
}
So the function is signaled by triggering the newproject action. If i call the function directly from within the constructor it disables it as you stated patrice, however, if I have the function called via the trigger, it doesn't disable it. Am I handling the signal / slot mechanism wrong? Thanks again.
Another example, if I make the function create_vipro() as below
void Main_Screen::Create_ViPro()
{
_fileMenu->setEnabled(false);
}
The file menu isn't disabled when I trigger the event, so it must have nothing to do with the modal itself, but instead how signals are handled.
Since child is a modal dialog main screen can't react to event. But you can disable the toolbar (or menubar) before creating the modal dialog and enable it as soon as you leave the exec function:
void Main_Screen::Create_ViPro()
{
_fileMenu->setEnabled(false);
std::auto_ptr<ViPro_Dialog> modal(new ViPro_Dialog(this));
modal->show();
modal->exec(); // Will stay here until you close the modal dialog
_fileMenu->setEnabled(true);
}
if ViPro_Dialog is really a modal dialog it will works.
Another thing, since ViPro_Dialog is modal you can declare it locally without using auto_ptr:
void Main_Screen::Create_ViPro()
{
_fileMenu->setEnabled(false);
ViPro_Dialog modal(this);
modal.show();
modal.exec(); // Will stay here until you close the modal dialog
_fileMenu->setEnabled(true);
}
EDIT:
I guess (I can't test at work) that you can't enable/disable menu when it is executing a QAction. Signal is calling slots sequentially so QAction is busy when you try to disable the menu.
Try this:
In Main Screen, create a slot with one boolean parameter that enable/disable menubar. Just call the setEnabled function
In ViPro_Dialog, emit a signal with a boolean parameter (false at startup, true at validation)
In Create_ViPro, once dialog created, connect the new signal with the slot, exec dialog and don't forget to disconnect slot from signal:
void Main_Screen::Create_ViPro()
{
ViPro_Dialog modal(this);
// Connect signal/slot
modal.show();
modal.exec(); // Will stay here until you close the modal dialog
// Disconnect signal/slot
}
This can achieve what you want
EDIT2
You are doing a mistake when using modal dialog. There's a conflict between show() and exec(). When you are displaying modal dialog you don't need to disable other windows: it's automatically done by modal status of the dialog. There are many modal depth: http://qt-project.org/doc/qt-4.8/qt.html#WindowModality-enum. So your code should be:
void Main_Screen::Create_ViPro()
{
ViPro_Dialog modal(this);
// modal.setWindowModality(Qt::WindowModal); // Uncomment this line if you want to only disable parent
modal.exec();
}
Read this for more detail: http://qt-project.org/doc/qt-4.8/QDialog.html#details.
Using exec() doesn't just create a modal dialog, it also suspends most of the regular event handling, and only handles events in the dialog that is in exec(). This may include some UI updates (like the transitions from enabled to disabled), but I'm not positive. A better way to handle this might be to explicitly set the dialog modal, but allow the regular event loop to continue, something like this:
void Main_Screen::Create_ViPro()
{
ViPro_Dialog* modal = new ViPro_Dialog(this);
modal->setModal(true);
modal->show();
}
That code will still not visually disable the toolbar or menubar, but they should be unresponsive. To disable them, you could try combining this with Patrice Bernassola's answer.