Slots and signals from different classes

[nicky j]

Okay so ive gotten my program to compile. but when I click the addTabButton, it does nothing. The compiler outputs: "QObject::connect: Cannot connect QToolButton::clicked() to (null)::newTab()"

here is the code:

browseTab.h:
@#ifndef BROWSETAB_H
#define BROWSETAB_H

#include <QWidget>
#include <QPointer>
#include <QLineEdit>
#include <QWebView>
#include <QToolBar>

#include "mainview.h"
#include <mainview.h>

class mainView;

class browseTab : public QWidget
{
Q_OBJECT
public:
explicit browseTab(QWidget *parent = 0);

signals:

protected slots:
void makeSearchURL();
void makeSearch();
void changeText();
void changeTabText();

private:
QWebView *webView;
QToolBar *navBar;
QLineEdit *URLbar;
QLineEdit *SearchBar;
QToolButton *addTabButton;
mainView *mainView_object_pointer;

};

#endif // BROWSETAB_H
@

browsetab.cpp:

@#include "browsetab.h"
#include "mainview.h"

#include <QtWidgets>

browseTab::browseTab(QWidget *parent) :
QWidget(parent),
mainView_object_pointer()
{
addTabButton = new QToolButton;
addTabButton->setText("+");
connect(addTabButton, SIGNAL(clicked()), mainView_object_pointer, SLOT(newTab()));
}
@

mainview.h:

@#ifndef MAINVIEW_H
#define MAINVIEW_H

#include <QMainWindow>
#include <QToolButton>
#include <QMessageBox>

#include "apptab.h"
#include "browsetab.h"
#include "novablastreceiver.h"
#include "novablastsender.h"

class mainView : public QMainWindow
{
Q_OBJECT

public:
mainView(QWidget *parent = 0);
~mainView();

signals:

public slots:
void newTab();

protected slots:
void newWindow();
void closeTab(int index);
void newAppTab();

void setFullscreen();
void setMaximized();
void setWindowed();

void startNBSender();
void startNBReceiver();

private:
QTabWidget *tabWidget;
QToolButton *newTabButton;
QToolButton *newAppTabButton;
QToolButton *menuButton;
QAction *NBSenderAction;
QAction *NBReceiverAction;
QAction *FullscreenAction;
QAction *MaximizedAction;
QAction *WindowedAction;
QAction *NewWindowAction;
QAction *NewTabAction;
QAction *AppsAction;
QAction *BookmarksAction;
QAction *HistoryAction;
appTab *Apps;
QMenu *menuButtonMenu;
QMenu *toolMenu;
QMenu *viewMenu;
QWidget *mainWidget;
QDialog *receiverDialog;
QDialog *senderDialog;
Receiver *newNBReceiver;
Sender *newNBSender;

};

#endif // MAINVIEW_H
@

mainview.cpp:

@#include <QtWidgets>

#include "mainview.h"

mainView::mainView(QWidget *parent)
: QMainWindow(parent)
{
void mainView::newTab()
{
tabWidget->addTab(new browseTab, tr("Search"));
}
}
@

How can I make the addTabButton actually call the newTab() slot in main view.cpp

It doesn't seem to work

[kpks]

i am pretty new too, but, I don't see where you assign your pointer to the mainview.

[eyenov]

if you are doing the "connect" call inside one of your mainView's functions, you can call it like this:

@connect(addTabButton, SIGNAL(clicked()), this, SLOT(newTab()));@

It should work...

[nicky j]

The connect is being called from browseTab, and the slot I want executed is in mainView. Help would be greatly appreciated!

[eyenov]

Change your browsetab.cpp to:

@#include "browsetab.h"
#include "mainview.h"

#include <QtWidgets>

browseTab::browseTab(QWidget *parent) :
QWidget(parent),
mainView_object_pointer(parent->parent())
{
addTabButton = new QToolButton;
addTabButton->setText("+");
connect(addTabButton, SIGNAL(clicked()), mainView_object_pointer, SLOT(newTab()));
}@

And when creating the tab, change to this:

@
#include <QtWidgets>

#include "mainview.h"

mainView::mainView(QWidget *parent)
: QMainWindow(parent)
{

//you should create tabWidget passing this as a parameter
tabWidget = new QTabWidget(this);

}

void mainView::newTab()
{
tabWidget->addTab(new browseTab(tabWidget), tr("Search"));
}
@

dont forget that when creating your tabWidget object (in mainView constructor?)you need to pass 'this' pointer for the mainView in the constructor,

hope this helps...

[nicky j]

Okay, although it compiles and runs, the button in the browseTab still won't create a new tab.

It gives me this error: "QObject::connect: Cannot connect QToolButton::clicked() to (null)::newTab()"

How do I fix this?
remember the addTab button is in browseTab, and newTab() is in mainView

[eyenov]

Are you sure you changed the way your QTabWidget is being created to:
@tabWidget = new QTabWidget(this);@

Just to give you a brief explanation:

1. you need to create your "tabWidget" with "this" (mainView) as a parent so you can access it on "browseTab" constructor
2. in "addTab" you need to create your "browseTab" object with "tabWidget" as a parent so you can access it on "browseTab" constructor
3. you need to set "mainView_object_pointer" to "browseTab" parent's parent
4. you need to connect "clicked" signal from "addTabButton" to slot "newTab" on "mainView_object_pointer"

if you are following this, then your "mainView_object_pointer" can't be null as you are saying in the error message.

[nicky j]

Ok so I think my problem is number 2. How can I make browseTab with tabWidget as a parent? Thanks for the help!

[eyenov]

In your "newTab" function create your new "browseTab" object with "tabWidget" as a parameter.

@void mainView::newTab()
{
tabWidget->addTab(new browseTab(tabWidget), tr("Search"));
}@

[nicky j]

Okay Ive tried that and now I get an error:

"error: cannot initialize a member subobject of type 'mainView *' with an rvalue of type 'QObject *'
mainView_object_pointer(parent->parent())"

[eyenov]

In browseTab.h where you have:
@mainview *mainView_object_pointer;@

change to:
@QObject *mainView_object_pointer;@

[nicky j]

hmmmm, just did that. The program appears to compile just fine and starts to run (the icon on the dock starts to bounce), it crashes and says "the program has unexpectedly finished" which is obviously not very helpful. I am running Qt Creator on OS X 10.9 if that matters. What do I do?

[eyenov]

You can send me the code if you want to for me to check it out, Will it run on windows or does it have any macosx dependencies?

[nicky j]

browseTab.h:
@#ifndef BROWSETAB_H
#define BROWSETAB_H

#include <QWidget>
#include <QPointer>
#include <QLineEdit>
#include <QWebView>
#include <QToolBar>
#include <QObject>

#include "mainview.h"
#include <mainview.h>

class mainView;

class browseTab : public QWidget
{
Q_OBJECT
public:
explicit browseTab(QWidget *parent = 0);

signals:

protected slots:
//void makeSearchURL();
void makeSearch();
void changeText();
void changeTabText();

private:
QWebView *webView;
QToolBar *navBar;
//QLineEdit *URLbar;
QLineEdit *SearchBar;
QToolButton *addTabButton;
QObject *mainView_object_pointer;

};

#endif // BROWSETAB_H
@

browseTab.cpp:
@#include "browsetab.h"
#include "mainview.h"

#include <QtWidgets>

browseTab::browseTab(QWidget *parent) :
QWidget(parent),
mainView_object_pointer(parent->parent())
{
QString url = "http://www.google.com";

webView = new QWebView;
webView->load(url);
connect(webView, SIGNAL(loadFinished(bool)), SLOT(changeText()));
connect(webView, SIGNAL(loadFinished(bool)), SLOT(changeTabText()));

/*
URLbar = new QLineEdit(this);
URLbar->setStyleSheet(
"background-color:white;"
"color:black;"
"border:1px solid rgba(47, 74, 135);"
);
connect(URLbar, SIGNAL(returnPressed()), SLOT(makeSearchURL()));
*/
SearchBar = new QLineEdit(this);
SearchBar->setStyleSheet(
"background-color:white;"
"color:black;"
"border:1px solid black;"
"margin-top:0px;"
"margin-bottom:0px;"
);
connect(SearchBar, SIGNAL(returnPressed()), SLOT(makeSearch()));

addTabButton = new QToolButton;
addTabButton->setText("+");
connect(addTabButton, SIGNAL(clicked()), mainView_object_pointer, SLOT(newTab()));

QToolBar *navBar = new QToolBar;
navBar->setStyleSheet(
            "height:20px;"
            );
navBar->addAction(webView->pageAction(QWebPage::Back));
navBar->addAction(webView->pageAction(QWebPage::Forward));
navBar->addAction(webView->pageAction(QWebPage::Reload));
navBar->addAction(webView->pageAction(QWebPage::Stop));
//navBar->addWidget(URLbar);
navBar->addWidget(SearchBar);
navBar->addWidget(addTabButton);

QVBoxLayout *browseTabLayout = new QVBoxLayout;
browseTabLayout->addWidget(navBar);
browseTabLayout->addWidget(webView);
setLayout(browseTabLayout);

}

//browseTab-- SLOTS

void browseTab::changeText()
{
SearchBar->setText(webView->url().toString());
}

void browseTab::changeTabText()
{

}
/*
void browseTab::makeSearchURL()
{
webView->setUrl(URLbar->text());
}
*/
void browseTab::makeSearch()
{
QString input = SearchBar->text();
QUrl query = SearchBar->text();
QString google = "/google";
QString newsfly = "/newsfly";

if(input.startsWith("http://"))
{
    webView->setUrl(query);
}

else
{
    if(input.startsWith("%"))
    {
        if(input == google)
        {
            webView->setUrl(QUrl(QString("http://www.google.com/")));
        }

        if(input == newsfly)
        {
            webView->setUrl(QUrl(QString("http://www.newsfly.x10.mx/")));
        }
    }

    else
    {
        webView->setUrl(QUrl(QString("http://www.google.com/search?fs&q=")+(SearchBar->text())));
    }
}

}

@

mainview.h:
@#ifndef MAINVIEW_H
#define MAINVIEW_H

#include <QMainWindow>
#include <QToolButton>
#include <QMessageBox>

#include "apptab.h"
#include "browsetab.h"
//#include "novablastreceiver.h"
//#include "novablastsender.h"

class mainView : public QMainWindow
{
Q_OBJECT

public:
mainView(QWidget *parent = 0);
~mainView();

signals:

public slots:
void newTab();

protected slots:
void newWindow();
void closeTab(int index);
void newAppTab();
void setFullscreen();
void setMaximized();
void setWindowed();
//void startNBSender();
//void startNBReceiver();

private:
QTabWidget *tabWidget;
QToolButton *newTabButton;
QToolButton *newAppTabButton;
QToolButton *menuButton;
QAction *NBSenderAction;
QAction *NBReceiverAction;
QAction *FullscreenAction;
QAction *MaximizedAction;
QAction *WindowedAction;
QAction *NewWindowAction;
QAction *NewTabAction;
QAction *AppsAction;
QAction *BookmarksAction;
QAction *HistoryAction;
appTab *Apps;
QMenu *menuButtonMenu;
QMenu *toolMenu;
QMenu *viewMenu;
QWidget *mainWidget;
QDialog *receiverDialog;
QDialog *senderDialog;
//Receiver *newNBReceiver;
//Sender *newNBSender;

};

#endif // MAINVIEW_H
@

fair warning: there is a lot of code to sift through, but much of it is commented out, and you appear to be a great programmer so you shouldn't have any trouble. Thanks for your time!

[nicky j]

mainview.cpp:
@#include <QtWidgets>

#include "mainview.h"

mainView::mainView(QWidget parent)
: QMainWindow(parent)
{
/
NBSenderAction = new QAction(tr("Start NovaBlast Sender"), this);
connect(NBSenderAction, SIGNAL(triggered()), SLOT(startNBSender()));

NBReceiverAction = new QAction(tr("Start NovaBlast Receiver"), this);
connect(NBReceiverAction, SIGNAL(triggered()), SLOT(startNBReceiver()));

*/
QMenu *toolMenu = new QMenu("Tools");
//toolMenu->addAction(NBSenderAction);
//toolMenu->addAction(NBReceiverAction);

FullscreenAction = new QAction(tr("Fullscreen"), this);
connect(FullscreenAction, SIGNAL(triggered()), SLOT(setFullscreen()));

MaximizedAction = new QAction(tr("Maximize"), this);
connect(MaximizedAction, SIGNAL(triggered()), SLOT(setMaximized()));

WindowedAction = new QAction(tr("Window"), this);
connect(WindowedAction, SIGNAL(triggered()), SLOT(setWindowed()));

QMenu *viewMenu = new QMenu("View");
viewMenu->addAction(FullscreenAction);
viewMenu->addAction(MaximizedAction);
viewMenu->addAction(WindowedAction);

NewWindowAction = new QAction(tr("New Window"), this);
connect(NewWindowAction, SIGNAL(triggered()), SLOT(newWindow()));

NewTabAction = new QAction(tr("New Tab"), this);
connect(NewTabAction, SIGNAL(triggered()), SLOT(newTab()));

AppsAction = new QAction(tr("Apps"), this);
connect(AppsAction, SIGNAL(triggered()), SLOT(newAppTab()));

BookmarksAction = new QAction(tr("Bookmarks"), this);

HistoryAction = new QAction(tr("History"), this);

//menuButtonMenu contains the above QActions, and viewMenu.
QMenu *menuButtonMenu = new QMenu("Menu");
menuButtonMenu->addAction(NewWindowAction);
menuButtonMenu->addAction(NewTabAction);
menuButtonMenu->addAction(AppsAction);
menuButtonMenu->addAction(BookmarksAction);
menuButtonMenu->addAction(HistoryAction);
menuButtonMenu->addSeparator();
menuButtonMenu->addMenu(viewMenu);
menuButtonMenu->addMenu(toolMenu);

//newTabButton creates a new browseTab.
newTabButton = new QToolButton;
newTabButton->setText("+");
newTabButton->setStyleSheet(
             "background-color:rgba(229, 239, 251);"
             "color:black;"
             "border:1px solid black;"
             "margin-bottom:0px;"
             );
connect(newTabButton, SIGNAL(released()), SLOT(newTab()));

//newAppTabButton creates a new appMenu tab.
newAppTabButton = new QToolButton;
newAppTabButton->setText("Apps");
newAppTabButton->setStyleSheet(
            "background-color:rgba(229, 239, 251);"
            "color:black;"
            "border:1px solid black;"
            "margin-bottom:0px;"
            );
connect(newAppTabButton, SIGNAL(released()), SLOT(newAppTab()));

//menuButton contains menuButtonMenu.
menuButton = new QToolButton;
menuButton->setText("|||");
menuButton->setStyleSheet(
            "background-color:rgba(229, 239, 251);"
            "color:black;"
            "border:1px solid black;"
            "border-top:0px;"
            "border-left:1px solid black;"
            "border-right:1px solid black;"
            "border-bottom:1px solid black;"
            "margin-bottom:0px;"
            "float:left;"
            "width:50px;"
            );
menuButton->setPopupMode(QToolButton::InstantPopup);
menuButton->setMenu(menuButtonMenu);

//creates a tabWidget containing a BrowseTab.
tabWidget = new QTabWidget(this);
tabWidget->addTab(new browseTab, tr("Search"));
tabWidget->setTabsClosable(true);
tabWidget->setTabShape(QTabWidget::Rounded);
tabWidget->setStyleSheet(
            "color:black;"
            "QTabBar::tab { height: 5px; width: 100px; }"
            );
connect(tabWidget, SIGNAL(tabCloseRequested(int)), SLOT(closeTab(int)));

//contains several buttons.
QHBoxLayout *topRowLayout = new QHBoxLayout;
topRowLayout->addWidget(menuButton);
topRowLayout->addWidget(newTabButton);
topRowLayout->addWidget(newAppTabButton);

//contains a tabWidget with topRowLayout on top.
QVBoxLayout *mainLayout = new QVBoxLayout;
mainLayout->addLayout(topRowLayout);
mainLayout->addWidget(tabWidget);
setLayout(mainLayout);

//contains mainLayout.
mainWidget = new QWidget;
mainWidget->setLayout(mainLayout);

setUnifiedTitleAndToolBarOnMac(true);
setCentralWidget(mainWidget);

}

mainView::~mainView()
{
}

//mainView--SLOTS
void mainView::setFullscreen()
{
this->setWindowState(Qt::WindowFullScreen);
}

void mainView::setMaximized()
{
this->setWindowState(Qt::WindowMaximized);
}

void mainView::setWindowed()
{
this->setWindowState(Qt::WindowMinimized);
}

void mainView::newWindow()
{
mainView newWindow;
newWindow.show();
}

void mainView::newTab()
{
tabWidget->addTab(new browseTab(tabWidget), tr("Search"));
}

void mainView::closeTab(int index)
{
tabWidget->removeTab(tabWidget->currentIndex());
}

void mainView::newAppTab()
{
tabWidget->addTab(new appTab, tr("App Menu"));
}@

[eyenov]

where you have in your mainView constructor:
@tabWidget->addTab(new browseTab, tr("Search"))@

please change it to:
@tabWidget->addTab(new browseTab(tabWidget), tr("Search"));@

just as in mainView::newTab()

hope it works.

best,
--rb

[nicky j]

Okay I have partial success! When the program starts it automatically creates a tab, when i press the addTab button inside this tab it creates another tab, but the addTab button in these new tabs doesn't work. What do I do? Thanks!

[eyenov]

Ok. It seems you have a different hierarchy for these objects. Let's keep it simple. In browseTab::browseTab change the code to:
@
browseTab::browseTab(QWidget *parent) :
QWidget(parent),
mainView_object_pointer(parent)
{
@

In mainview.cpp, change everything from:
@new browseTab(tabWidget)@
to
@new browseTab(this)@

It should work fine.

[nicky j]

Success! It works, but I don't quite understand how.
Thanks for all of your help!

[nicky j]

sorry to resurrect this thread, but I am having a similar problem again. I have created two new classes: sideBar and sideBar_appView. the mainView class has a QDockWidget in it that contains sideBar. Inside sideBar there is a QTabWidget that creates a new tab populated by sideBar_appView. Within sideBar_appView there is a button that is supposed to call mainView::newAppTab. However it does nothing when clicked.

code:

sidebar.h:
@#ifndef SIDEBAR_H
#define SIDEBAR_H

#include "sidebar_appview.h"
#include "mainview.h"
#include <mainview.h>
#include <QPointer>
#include <QObject>
#include <QWidget>
#include <QWebView>
#include <QVBoxLayout>
#include <QTabWidget>
#include <QTextEdit>

class mainView;

class sideBar : public QWidget
{
Q_OBJECT
public:
explicit sideBar(QWidget *parent = 0);

signals:

public slots:

private:
//sideBar_appView *appView;
QTabWidget *tabs;
QTextEdit *settingsView;
QObject *mainView_object_pointer;
};

#endif // SIDEBAR_H@

sidebar.cpp:
@#include "sidebar.h"
#include "mainview.h"

#include <QtWidgets>

sideBar::sideBar(QWidget *parent) :
QWidget(parent),
mainView_object_pointer(parent)
{
QString url = "http://www.google.com";

settingsView = new QTextEdit;

tabs = new QTabWidget;
tabs->setTabPosition(QTabWidget::West);
tabs->setStyleSheet(
            "QTabBar::tab { width: 25px; }"
            );
tabs->addTab(new sideBar_appView(this), tr("Apps"));
tabs->addTab(settingsView, tr("Settings"));

QVBoxLayout *layout = new QVBoxLayout;
layout->setMargin(0);
layout->addWidget(tabs);
setLayout(layout);

}
@

sidebar_appview.h
@#ifndef SIDEBAR_APPVIEW_H
#define SIDEBAR_APPVIEW_H

#include <QPointer>
#include <QObject>
#include <QWidget>
#include <QToolButton>
#include <QVBoxLayout>
#include "mainview.h"
#include <mainview.h>
//#include "sidebar.h"
//#include <sidebar.h>

class mainView;

class sideBar_appView : public QWidget
{
Q_OBJECT
public:
explicit sideBar_appView(QWidget *parent = 0);

signals:

public slots:

private:
QToolButton *runAntivirusButton;
QToolButton *viewAllAppsButton;

QObject *mainView_object_pointer;

};

#endif // SIDEBAR_APPVIEW_H
@

sidebar_appview.cpp:
@#include "sidebar_appview.h"
#include "mainview.h"
//#include "sidebar.h"

#include <QtWidgets>

sideBar_appView::sideBar_appView(QWidget *parent) :
QWidget(parent),
mainView_object_pointer(parent)
{
runAntivirusButton = new QToolButton;
runAntivirusButton->setText("Run Antivirus");

viewAllAppsButton = new QToolButton;
viewAllAppsButton->setText("All Apps ->");
connect(viewAllAppsButton, SIGNAL(clicked()), mainView_object_pointer, SLOT(newAppTab()));

QVBoxLayout *appViewLayout = new QVBoxLayout;
appViewLayout->setMargin(0);
appViewLayout->addWidget(runAntivirusButton);
appViewLayout->addWidget(viewAllAppsButton);
setLayout(appViewLayout);

}@