I have looked at a variety of the Qt discussions for this error "no matching function for call to" and I still cannot see what is different in this case. I have successfully set up slot/signal pairs between GUI elements, but for some reason the latest set of slot/signal pairs is creating an error.
In order to allow all GUI elements to update the status bar on the main window I have created a signal in each panel as shown here
class PanelA : public QWidget
{
...
public signals:
void UpdateStatusBar(std::string);
...
}
Then in MainWindow there is a slot
//from MainWindow.h
class MainWindow : public QMainWindow
{
private slots:
void ReceiveStatus(std::string);
}
//from MainWindow.cpp
void MainWindow::ReceiveStatus(std::string s)
{
//I can provide other controls, filters, etc.
//but currently there are none
ui->statusBar->showMessage(tr("System status: "+s));
}
And finally, in the MainWindow constructor I have several signals already and I have added one new connect line for each GUI element.
connect(ui->panelA, &PanelA::SelectionChanged, ui->panelB, &PanelB::UpdateSelection);
//this one works
connect(ui->panelA, &PanelA::UpdateStatusBar, ui, &MainWindow::ReceiveStatus);
//this one generates an error there is one status bar connection for each
So, as far as I can tell the syntax is right. both ui->panelA and ui are pointers. I don't know why one is correct and the other is wrong. I'd appreciate any suggestions.
Probably should be:
connect(ui->panelA, &PanelA::UpdateStatusBar, this, &MainWindow::ReceiveStatus);
The ui object isn't a MainWindow, but this will be.
Related
I know this is very clunky and I'm probably doing a lot of wrong things but so far everything I saw on the net gives back the same errors: invalid use of non-static data member ui.
So in the MainWindow, I have a comboBox named hometeam, and I want to display the currentText on a Qlabel named label which is on another Form Class called Dialog
I figured they're both private members so I added friend class MainWindow and friend class dialog in the respective headers (I know this is pretty wrong but it's the last thing I tried), I included the "ui_mainwindow" and "ui_dialog" in the .cpp files, and here's the bit of code I'm trying:
ui->label->setText(MainWindow::ui->hometeam->currentTex());
Keep in mind that I don't want a QDialog, the second window will do a lot more than a display, I just want to access the objects from a different window. Slots and signals give the same error.
Thanks !
I think the proper way to do that, is to add a function to your MainWindow class:
QString hometeamText() const
{
return ui->hometeam->currentTex();
}
This way you can access the information you need without violating encapsulation rules, but you need an instance of MainWindow to do it, and sure must keep a pointer to it in your Dialog class:
class Dialog
{
private:
MainWindow * mainwindow;
public:
void setMainWindow(MainWindow * w) { mainWindow = w; }
then somewhere (e.g. in main) you can do something like:
MainWindow mainwindow;
Dialog dialog;
dialog.setMainWindow(&mainWindow);
and from inside your Dialog class, wherever you need it:
ui->label->setText(window->hometeamText());
I have a MainWindow with two widgets, buttonsWidget and infoWidget.
I'm trying to to hide infoWidget after clicking a button within buttonsWidget (and ultimately show a different widget).
I've tried:
mainwindow.h
public:
void hideInfo();
mainwindow.cpp
void MainWindow::hideInfo()
{
ui->info->hide();
}
buttonsWidget.cpp
void buttonsWidget::on_timingButton_clicked()
{
MainWindow::hideInfo();
//Then will do something to show 'timingWidget'..
}
Many thanks
You should use Signals and Slots for this.
Add a signal in the buttonsWidget.h.
signals:
void hideInfoSignal();
In the main function, connect the button signal with the mainwindow method hideInfo().
QObject::connect(this->info, SIGNAL(hideInfoSignal),this, SLOT(hideInfo));
I haven't tested this, because I dont have Qt on this machine, but that should work, with possible minor modifications. If any errors appear, let me know and I will help. Also, read the signals and slots documentation.
I've tried virtually every way possible to hook the activated() signal of a taskbar icon to a corresponding slot. However, I do not understand why Qt(Qt5 Cretor) says I don't have a matching function for the slot.
Qt Error:
C:\Users\potato\Desktop\CCT-master\CCTracker\cctsystemtray.cpp:40:
error: no matching function for call to
'QObject::connect(QSystemTrayIcon*&, const char*, CCTSystemTray*
const, const char*)'this,
SLOT(systrayActivated(QSystemTrayIcon::ActivationReason)))
As far as I can tell, according to Qt Documentation,
The activated() signal is used to catch mouse events such as clicks and double clicks for the taskbar icon. At first try I thought it's only signals and slots, but then for whatever reason activated() just won't fit. And If I try connecting activated() to a slot from another class, everything fails due to pointer errors.
Here's are the working parts inside CCTSystemTray.h:
class CCTSystemTray
{
public:
CCTSystemTray();
void initSystemTray(QWidget *rootWindow);
private:
QSystemTrayIcon* systray;
public slots:
void systrayActivated(QSystemTrayIcon::ActivationReason);
};
And CCTSystemTray.cpp:
// Above are Class declearations, menu items, etc...
QObject::connect(this->systray, SIGNAL(QSystemTrayIcon::activated(QSystemTrayIcon::ActivationReason reason)),
this, SLOT(systrayActivated(QSystemTrayIcon::ActivationReason)));
}
void CCTSystemTray::systrayActivated(QSystemTrayIcon::ActivationReason)
{
qDebug() << "Hello";
}
The full code sample can be found here on pastebin.
If someone can help me out from hair-pulling, that'd be great!
Thank you all.
Your class CCTSystemTray has a slot, but it is not a QObject (it doesn't derive from QObject or another class derived from QObject) and also you need the Q_OBJECT macro in your class declaration and then signals and slots will work.
I am creating a QSystemTrayIcon traymenu. Its contextmenu has several actions which I need to identify.
public slots:
void s_showNote();
void Traymenu::createMainContextMenu(){
...
std::string noteTitle = m_noteList[i]->getTitle();
QString menuEntryName = QString::fromStdString(noteTitle);
QAction *openNote = m_mainContextMenu.addAction(menuEntryName);
QObject::connect(openNote,SIGNAL(triggered() ),this,SLOT(s_showNote()) );
QVariant noteID;
noteID.setValue(m_noteList[i]->getID());
openNote->setData(noteID);
The error is
QObject::connect: No such slot QSystemTrayIcon::s_showNote()
All of the code above is a part of my class definition that inherits from QSystemTrayIcon. How can I call the SLOT?
You seem to have at least two issues ongoing:
Use Q_OBJECT for QObject derived classes.
You will need to re-run qmake correspondingly.
As for the first point, please use C++11 and at least Qt 5.2 in the future because in cases like this, you will get a static compiler time error which comes handy for avoiding these tedious issues.
I am just starting out with QT. I have read through some tutorials, and I think I have an understanding of signals and slots. I am writing a GUI that has various buttons that change the state of my main program. So for example in a drawing app, you would pick different drawing tools (using various buttons).
What is the best way to go about this? My first thought was to try to connect the clicked signal of the PushButton to some function that sets a current_tool variable. I did some searching and couldn't find a way to connect a QObject signal to a regular function.
This leads me to believe that there is probably a different approach. One where I create a new QObject (my own extension that is) that has various GUI properties. I would then define my slots here for the various buttons.
What is the best way to do this in QT. I am new and do not know of the preferred practice.
Any info would be useful,
thanks
You can define these "normal functions" as slots. Slots are just normal functions that can also be called by signals:
class ToolSelector : public QObject {
Q_OBJECT
public:
Tool *selected;
public slots:
void selectBrush();
void selectPen();
void selectFill();
};
ToolSelector::selectBrush() {
delete selected;
selected = new Brush();
}
ToolSelector::selectPen() {
// ...
}
// ...
toolsel = new ToolSelector();
brushButton = new QPushButton();
connect(brushButton, SIGNAL(clicked()), toolsel, SLOT(selectBrush()));
Inherit from the class that uic generates, creating, say, a MyAppWindow class. Provide extra METHODs in that class, as well as a Document or Drawing object. Connect these methods to the signals you're interested in, and them alter a member variable that contains the drawing state.