In Graphic View set the scene, In Graphic scene(subclass od QGraphicscene) class added Delete item slot.In scene class by delete key i able to delete item but when i call from main window it wont delete item . i am getting call in Delete item slot but selectedItems = 0. what may be causing problem?
In Graphic scene class
void GraphicScene::DeleteItems()//Delete Item slot in scene class
{
qDebug()<<"delete items"<< selectedItems().count();
foreach(QGraphicsItem* item, selectedItems())
{
removeItem(item);
delete item;
}
}
void GraphicScene::keyReleaseEvent(QKeyEvent * keyEvent)// Delete key works fine
{
if (selectedItems().isEmpty())
return;
if(keyEvent->key() == Qt::Key_Delete)
{
DeleteItems();
}
}
In MainWindow class
MainWindow::MainWindow(QWidget *parent)
{
addToolBar(Qt::TopToolBarArea, mpEditToolbar = new
QToolBar());
DeleteAction = new QAction(QIcon(":/images/delete.png"),tr("Object
&Delete"), this);
DeleteAction->setStatusTip(tr("Delete item"));
connect(DeleteAction,SIGNAL(triggered()),mpGraphView ,
SIGNAL(DeleteObject())); // grpah view connecting to delete slot
mpEditToolbar->addAction(DeleteAction);
}
When i do from delete key works fine its not working with tool box delete action. what is the problem?
In Main Window class have private members of GraphicsView and GraphicScene class(subclass)
so that it will be easy to call slot.
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private:
GraphFrame *mpGraphFrame;
GraphicScene *mpScene;
}
MainWindow.cpp
Connect should be in where you creating GraphicScene Object
MainWindow::MainWindow(QWidget *parent)
{
addToolBar(Qt::TopToolBarArea, mpEditToolbar = new
QToolBar());
DeleteAction = new QAction(QIcon(":/images/delete.png"),tr("Object
&Delete"), this);
DeleteAction->setStatusTip(tr("Delete item"));
connect(DeleteAction,SIGNAL(triggered()),mpGraphScene ,
DeleteItems();
mpEditToolbar->addAction(DeleteAction);
}
So what I am trying to do is when I press the showMenu (QAction), the container (QStackedWidget) changes the current widget to menuWidget AND when I press it again it hides.
Ok so I have managed to get this code:
connect(showMenu, SIGNAL(triggered()), map, SLOT(map()));
map->setMapping(menuWidget, container);
Object::connect(map, SIGNAL(mapped(QWidget *)), container, SLOT(setCurrentWidget(QWidget *)));
also if I run:
container->setCurrentWidget(menuWidget);
directly, it works fine, so I have not messed up in that way.
You should create a slot in your class where you show/hide menuWidget.
If you are using a checkable QAction object, then you can use QAction::toggled(bool checked) signal, and use the checked variable to determine if you should show or hide your widget.
If you're not using a checkable QAction object, then you should create a class member variable of type bool that you toggle in your slot:
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
...
private:
bool toggleStatus; // set this to false in your constructor
...
};
void MainWindow::menuToggled()
{
toggleStatus = !toggleStatus;
if(toggleStatus)
{
container->setCurrentWidget(menuWidget);
}
else
{
container->setCurrentWidget(mdiContainer);
}
}
I have third party widget which provides me some context menu. Lets say cut, copy paste, select all.
Now I just want to modify only the paste functionality of the existing context menu. I know that I can implement whole context menu from scratch in the contextMenuEvent. But I do not want to do that as I am satisfied with other context menu actions, and just want to modify only the paste functionality.
I am using QT 4.8 on Mac OSX.
If such a thing is not possible at the moment can someone give me link/reference for that ? So that I can satisfy my stakeholders.
Edit: To be more clearer on what I am trying to do is, disable the paste context menu for some reason, and want to enable it later on depending on the situation/events.
I'm not sure that it can be done in a common way.
Here is a tricky solution:
In contextMenuEvent create a queued call to some slot:
QMetaObject::invokeMethod(this, "patchMenu", Qt::QueuedConnection);
Get visible windows in the slot and find QMenu. Get actions out of it and enable/disable them:
Q_SLOT patchMenu()
{
QWidgetList widgets = QApplication::topLevelWidgets();
foreach (QWidget* widget, widgets)
{
if (QMenu* menu = qobject_cast<QMenu*>(widget))
{
QList<QAction*> actions = menu->actions();
// here you can either get an action by index actions[5]
// or search the action by text
actions;
}
}
}
EDIT:
Here is a working example which demonstrates this approach:
window.h
#pragma once
#include <QtGui>
class Window: public QMainWindow
{
Q_OBJECT
public:
Window(QWidget *parent = 0);
};
class A : public QWidget
{
public:
virtual void contextMenuEvent(QContextMenuEvent* e);
};
class B : public A
{
Q_OBJECT;
public:
virtual void contextMenuEvent(QContextMenuEvent*);
Q_SLOT void patchMenu();
};
window.cpp
#include "window.h"
Window::Window(QWidget *parent) : QMainWindow(parent)
{
setCentralWidget(new B());
}
void B::patchMenu()
{
QWidgetList widgets = QApplication::topLevelWidgets();
foreach (QWidget* widget, widgets)
{
if (QMenu* menu = qobject_cast<QMenu*>(widget))
{
QList<QAction*> actions = menu->actions();
// here you can either get an action by index actions[5]
// or search the action by text
actions;
}
}
}
void B::contextMenuEvent(QContextMenuEvent* e)
{
QMetaObject::invokeMethod(this, "patchMenu", Qt::QueuedConnection);
A::contextMenuEvent(e);
}
void A::contextMenuEvent(QContextMenuEvent* e)
{
QMenu menu;
QAction* action = new QAction(QIcon(), "text", &menu);
menu.addAction(action);
menu.exec(e->globalPos());
}
from my main window I am launching a dialog which has a label, in which I am trying to paint.
So, the dialog's header file (.h) has two classes, one for the dialog itself and one for my label. So, my label's class is this:
class MyImage : public QLabel
{
Q_OBJECT
public:
explicit MyImage(QWidget *parent = 0);
protected:
void paintEvent(QPaintEvent *e);
};
and in the .cpp, along with the constructor of my QDialog I have the constructor of my MyImage class and the paintEvent function:
MyImage::MyImage(QWidget *parent)
: QLabel(parent)
{
/*...*/
}
void MyImage::paintEvent(QPaintEvent *e)
{
QLabel::paintEvent(e);
QPainter painter(image_label);
painter.setPen(QPen(QBrush(QColor(0,0,0,180)),1,Qt::DashLine));
painter.setBrush(QBrush(QColor(255,255,255,120)));
painter.drawRect(selectionRect);
}
The image_label is a MyImage object. On the constructor of my QDialog I do the following so as to add it to my QDialog's layout:
mainLayout->addWidget(image_label);
But it is null. I get an error message on output (cannot add null widget) and when I try to add a pixmap to the image_label the program crashes.
Thanks in advance for any answers!
void MyImage::paintEvent(QPaintEvent *e)
{
// QPainter painter(image_label); <- Only paint onto yourself.
QPainter painter(this);
painter.setPen(QPen(QBrush(QColor(0,0,0,180)),1,Qt::DashLine));
painter.setBrush(QBrush(QColor(255,255,255,120)));
painter.drawRect(selectionRect);
}
Do not call the base class as any output will be overwritten by the new QPainter. It is crashing because image_label is null.
For my GUI i would like to have two pairs of buttons that scroll up and down a scrollarea. The first set of buttons should work on say scrollarea1 and the second set of buttons should work on a scrollarea2. The widgets that I put in the scrollarea are called viewport1 and viewport2.
Since both both set of buttons should do the same (scrolling up and down) I thought I would make two slots called scrollUp and scrollDown that would handle the scrolling for both sets of buttons. Unfortunately I cannot make this work and need some help. I have tried the following:
QPushButton up;
QPushButton down;
QPushButton up2;
QPushButton down2;
connect(&up,SIGNAL(clicked()),&up,SLOT(scrollUp()));
connect(&up2,SIGNAL(clicked()),&up,SLOT(scrollUp()));
connect(&down,SIGNAL(clicked()),&down,SLOT(scrollDown()));
connect(&down2,SIGNAL(clicked()),&down,SLOT(scrollDown()));
void MainWindow::scrollDown()
{
QScrollArea area;
QWidget view;
if((QPushButton) &sender = down)
{
area=scrollArea;
view=viewport;
}
if((QPushButton) &sender = down2)
{
area=scrollArea;
view=viewport;
}
int curpos = area.verticalScrollBar()->value();
area.verticalScrollBar()->setValue(curpos+15);
int newpos = area.verticalScrollBar()->value();
QPoint topLeft = area.viewport()->rect().topLeft();
view.move(topLeft.x(),topLeft.y()-(newpos));
}
void MainWindow::scrollUp()
{
QScrollArea area;
QWidget view;
if((QPushButton) &sender = up)
{
area=scrollArea;
view=viewport;
}
if((QPushButton) &sender = up2)
{
area=scrollArea2;
view=viewport2;
}
int curpos = area.verticalScrollBar()->value();
area.verticalScrollBar()->setValue(curpos-15);
int newpos = area.verticalScrollBar()->value();
QPoint topLeft = area.viewport()->rect().topLeft();
view.move(topLeft.x(),topLeft.y()-(newpos));
}
But this doesn´t work for several reasons. I also tried giving the slot some arguments, something like:
connect(&up,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea1,viewport1)));
connect(&up2,SIGNAL(clicked()),&up,SLOT(scrollUp(scrollarea2,viewport2)));
But again, no succes. Can anybody help me?
First of all, "It doesn't work" does not mean anything, and it is hard to help you if you do not say what errors you get. Then, there are few problems.
All QObject's derived classes are not copiable, it means you can not do
QWidget a;
QWidget b;
b = a; // Wrong
You should use pointers (or perhaps references).
QWidget a;
QWidget * b = new QWidget(...);
QWidget * c;
c = & a; // Ok
c = b; // Ok
Then your connect calls are wrong:
connect(&up, SIGNAL(clicked()), &up, SLOT(scrollUp()));
The third argument is the object who has the slot. up is a QPushButton, it does not have a scrollUp() slot, it is your MainWindow who does:
connect(&up, SIGNAL(clicked()), this, SLOT(scrollUp()));
(since connect is called in MainWindow's constructor this points to the current MainWindow object).
Also in C++ the single = sign means assignment, for equality comparison use =='. Andsender` is a function.
Your approach should work if implemented in the right way:
class MainWindow: public QWidget
{
QScrollArea * scroll1;
QScrollArea * scroll2;
QWidget * view1;
QWidget * view2;
QPushButton * up1;
QPushButton * up2;
QPushButton * down1;
QPushButton * down2;
public:
MainWindow()
{
// Here initialize member variables.
...
connect(up1, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(up2, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(down1, SIGNAL(clicked()), this, SLOT(scrollDown()));
connect(down2, SIGNAL(clicked()), this, SLOT(scrollDown()));
}
public slots:
void scrollDown()
{
QScrollArea * area;
QWidget * view;
if(qobject_cast<QPushButton>(sender()) == down1) {
area = & scroll1;
view = & view1;
} else if(qobject_cast<QPushButton>(sender()) == down2) {
area = & scroll2;
view = & view2;
} else {
// Error.
}
// Now `area` and `view` point to the right widgets.
...
}
void scrollUp()
{
// The same as before.
}
};
Another approach would be to extract the actual scrolling instructions to a separate function:
class MainWindow: public QWidget
{
// Same variables as before
...
public:
MainWindow()
{
// Here initialize member variables.
...
connect(up1, SIGNAL(clicked()), this, SLOT(scrollUp1()));
connect(up2, SIGNAL(clicked()), this, SLOT(scrollUp2()));
connect(down1, SIGNAL(clicked()), this, SLOT(scrollDown1()));
connect(down2, SIGNAL(clicked()), this, SLOT(scrollDown2()));
}
public slots:
void scrollDown(QScrollArea * area, QWidget * view)
{
// Here you scroll over `area` and `view`.
}
void scrollDown1()
{
scrollDown(scroll1, area1);
}
void scrollDown2()
{
scrollDown(scroll2, area2);
}
// Again, the same for `scrollUp`.
};
There are several mistakes in your code :
About the sender of the signal : There is not a QObject called "sender" but a method QObject * QObject::sender() const; which returns a pointer on the sender of the signal.
In the if conditions : you are casting a QPushButton** into a QPushButton ((QPushButton) &sender) and you dont compare that thing with your buttons up(2) and down(2).
In your connections between slots and signals : the scrollUp and scrollDown slots do not belong to the QPushButton class but to your MainWindow class.
Finally, you should write something like this :
connect(&up, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(&up2, SIGNAL(clicked()), this, SLOT(scrollUp()));
connect(&down, SIGNAL(clicked()), this, SLOT(scrollDown()));
connect(&down2, SIGNAL(clicked()), this, SLOT(scrollDown()));
void MainVindow::scrollDown() {
// [...]
QPushButton * senderButton = qobject_cast<QPushButton *>(this->sender());
// QPushButton * senderButton = (QPushButton *) this->sender(); works too
if (senderButton == &down) {
// [...]
}
if (senderButton == &down2) {
// [...]
}
// [...]
}
void MainVindow::scrollUp() {
// [...]
QPushButton * senderButton = qobject_cast<QPushButton *>(this->sender());
// QPushButton * senderButton = (QPushButton *) this->sender(); works too
if (senderButton == &up) {
// [...]
}
if (senderButton == &up2) {
// [...]
}
// [...]
}
First of all the slot can have no other arguments than the signal hands to it. Clicked has no arguments and there fore the slot can have no arguments.
I would think that the easiest way to check whether scrollArea 1 or 2 has focus and decide from that which one should move.
I also think that there is an error in your code. Shouldn't this:
if((QPushButton) &sender = down2)
{
area=scrollArea;
view=viewport;
}
Be this:
if((QPushButton) &sender = down2)
{
area=scrollArea2;
view=viewport2;
}
First of all, this is pseudo code. It won't compile, but it should contain the necessary information.
I believe this problem can be most elegantly solved using the QSignalMapper class. It allows parameterless signals from multiple senders to connect to one slot.
In the header, write something like this:
class QSignalMapper;
class MainWindow : public QMainWindow
{
public:
void init();
public slots:
void handleScrollButtons(int id);
private:
enum { ScrollUp1, ScrollDown1, ScrollUp2, ScrollDown2 } // just makes it more convenient to use
QSignalMapper *m_scrollbuttonhandler;
}
In the source file, write something like this
#include <QSignalMapper>
void MainWindow::init()
{
m_scrollbuttonhandler = new QSignalMapper(this);
m_scrollbuttonhandler->setMapping(scrollup1button, ScrollUp1);
m_scrollbuttonhandler->setMapping(scrolldown1button, ScrollDown1);
m_scrollbuttonhandler->setMapping(scrollup2button, ScrollUp2);
m_scrollbuttonhandler->setMapping(scrolldown2button, ScrollDown2);
connect(scrollup1button, SIGNAL(clicked(bool)), m_scrollbuttonhandler, SLOT(map()));
connect(scrolldown1button, SIGNAL(clicked(bool)), m_scrollbuttonhandler, SLOT(map()));
connect(scrollup2button, SIGNAL(clicked(bool)), m_scrollbuttonhandler, SLOT(map()));
connect(scrolldown2button, SIGNAL(clicked(bool)), m_scrollbuttonhandler, SLOT(map()));
connect(m_scrollbuttonhandler, SIGNAL(mapped(int)), this, SLOT(handleScrollButtons(int)));
}
void MainWindow::handleScrollButtons(int id)
{
switch (id)
{
case ScrollUp1:
// stuff to do for scrollup1button
case ScrollDown1:
// stuff to do for scrolldown1button
case ScrollUp2:
// stuff to do for scrollup2button
case ScrollDown2:
// stuff to do for scrolldown2button
}
}