i'm very newbie and lost!
I have a .cpp file in my qt project and my own widget.cpp wich has drawings! Now i want to get the data from the other .cpp file, from a class called, outputtext..which has a method add(name,value) both std string!
Know i want in my widget.cpp to import this stings! I have a form and i put a button on it 'get string'-button!
Know i have
void Widget::on_pushButton_clicked(){
// how can i use Qpainter to deaw the text in my widget?
}
so, this is my widget class:
#include "widget.h"
#include "ui_widget.h"
#include "outputtext.h"
Widget::Widget(QWidget *parent) :
QWidget(parent),
ui(new Ui::Widget)
{
ui->setupUi(this);
}
Widget::~Widget()
{
delete ui;
}
void Widget::on_pushButton_clicked()
{
//int outputtext.add(name,value);
// i want to say get the name and value from outputtext class and draw it in the widget!
}
and the other cpp file (outputtext) as a method add(name, vale) as string:
unsigned int OutPutText::add( std::string name , std::string value )
{
.....
}
please help!! i think it is easy but I just can't get the painter works from the push-button!
problem solved:
in order to get the text and drawing in the widget from the on_pushButton_clicked, i had to use QPixmap and QGraphicsscene so that i have a Scene for the Paiter and to show the drawing on the widget i set the size for the Pixmap as so as the size of my widget and make the pixmap transparent...then i have to use QGraphicsviewer to let the scene shows on the widget like the code below!
thanks any way...
void Widget::on_pushButton_clicked()
{
QPixmap *pixmap = new QPixmap(this->size());
pixmap->fill(Qt::transparent);
QGraphicsScene *scene = new QGraphicsScene(this);
scene->addPixmap(*pixmap);
QPainter painter(pixmap);
painter.begin(pixmap);
painter.drawPixmap(QPoint(0,0), *pixmap);
painter.drawText(x,y,"my string");
painter.end();
QGraphicsView *view = new QGraphicsView(scene, this);
scene->addPixmap(*pixmap);
view->setStyleSheet("background: transparent");
view->setVerticalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
view->setHorizontalScrollBarPolicy(Qt::ScrollBarAlwaysOff);
view->show();
}
Related
I want to be able to change page of QStackedWidget with some kind of animation (like fade in/out or others...)
after some research I find out maybe its possible with QGraphicsOpacityEffect, then I found this codes in here
Fade In Your Widget
// w is your widget
QGraphicsOpacityEffect *eff = new QGraphicsOpacityEffect(this);
w->setGraphicsEffect(eff);
QPropertyAnimation *a = new QPropertyAnimation(eff,"opacity");
a->setDuration(350);
a->setStartValue(0);
a->setEndValue(1);
a->setEasingCurve(QEasingCurve::InBack);
a->start(QPropertyAnimation::DeleteWhenStopped);
Fade Out Your Widget
// w is your widget
QGraphicsOpacityEffect *eff = new QGraphicsOpacityEffect(this);
w->setGraphicsEffect(eff);
QPropertyAnimation *a = new QPropertyAnimation(eff,"opacity");
a->setDuration(350);
a->setStartValue(1);
a->setEndValue(0);
a->setEasingCurve(QEasingCurve::OutBack);
a->start(QPropertyAnimation::DeleteWhenStopped);
connect(a,SIGNAL(finished()),this,SLOT(hideThisWidget()));
// now implement a slot called hideThisWidget() to do
// things like hide any background dimmer, etc.
but looks like these codes have some problem when used in QWidget inside of QStackedWidget i mean widget successfully fade in and out, but after animation finish if I minimize the windows the widget will disappear completely! (Im still able to see widget in bottom right corner of my window, looks like its pos changed?!)
btw my program is frameless.
thanks for help.
here is a example from my problem
test.cpp
Test::Test(QWidget *parent)
: CustomMainWindow(parent)
{
ui.setupUi(this);
setShadow(ui.bg_app);
connect(ui.close_app_btn, &QPushButton::clicked, this, &QWidget::close);
connect(ui.minimize_app_btn, &QPushButton::clicked, this, &QWidget::showMinimized);
QGraphicsOpacityEffect* eff = new QGraphicsOpacityEffect(this);
ui.checking->setGraphicsEffect(eff); // checking is my widget inside of QStackedWidget.
QPropertyAnimation* a = new QPropertyAnimation(eff, "opacity");
a->setDuration(350);
a->setStartValue(0);
a->setEndValue(1);
a->setEasingCurve(QEasingCurve::InBack);
a->start(QPropertyAnimation::DeleteWhenStopped);
}
CustomMainWindow.cpp
CustomMainWindow::CustomMainWindow(QWidget *parent)
: QMainWindow(parent)
{
setWindowFlags(windowFlags() | Qt::Window | Qt::FramelessWindowHint | Qt::WindowSystemMenuHint);
setAttribute(Qt::WA_TranslucentBackground);
}
void CustomMainWindow::setShadow(QWidget* window)
{
QGraphicsDropShadowEffect* windowShadow = new QGraphicsDropShadowEffect;
windowShadow->setBlurRadius(9.0);
windowShadow->setColor(palette().color(QPalette::Highlight));
windowShadow->setOffset(0.0);
window->setGraphicsEffect(windowShadow);
}
when I run my program with this code, at first its successfully Fade In, but if I for example minimize the window the widget move from its original position to somewhere else, look at this gif
Note: MainWindow is the name of my class.
Header file:
//...
private slots:
void animationStackedWidgets();
void whenAnimationFinish();
//....
CPP file:
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->button, &QPushButton::clicked, this, &MainWindow::animationStackedWidgets);
}
MainWindow::~MainWindow()
{
delete ui;
}
void MainWindow::animationStackedWidgets()
{
QGraphicsOpacityEffect *effect = new QGraphicsOpacityEffect(this);
ui->stackedWidget->setGraphicsEffect(effect);
QPropertyAnimation *anim = new QPropertyAnimation(effectSw,"opacity");
anim->setDuration(350);
anim->setStartValue(0);
anim->setEndValue(1);
anim->setEasingCurve(QEasingCurve::InBack);
anim->start(QPropertyAnimation::DeleteWhenStopped);
connect(anim, SIGNAL(finished()), this, SLOT(whenAnimationFinish()));
}
void MainWindow::whenAnimationFinish()
{
ui->stackedWidget->setGraphicsEffect(0); // remove effect
}
I want to make a simple application with invisible button.
I set background image for my widget by UI property styleSheet and Resources -
border-image:url(:/image.jpg).
I always get something like this
and then I try to add button on it
I was trying with
ui->pushButton->setStyleSheet("QPushButton{background: transparent;}");
ui->pushButton->setStyleSheet("background-color: rgba(255, 255, 255, 0);");
and it works with buttons on default background, but not in my case.
Every button that I add takes default parent background image. I dont want to see any hints of a button, but when I click on an area to be able to perform some functionality.
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
ui->centralWidget->setStyleSheet("background-image:url(:image.jpg)");
ui->pushButton->setStyleSheet("QPushButton{border:none;}");
}
Code an above makes button flat, but it duplicate background image from parent widget anyway.
Have you any idea how to resolve it?
Cause
A common misconception is that when a stylesheet without a selector is applied to an element, then it is used only for that element. In fact all element's children are styled as well. Thus a selector should be used to achieve the expected result.
Solution
I would suggest you to change this line in your code
ui->centralWidget->setStyleSheet("background-image:url(:image.jpg)");
to
ui->centralWidget->setStyleSheet(".QWidget { background-image:url(:image.jpg) }");
Important: Note the dot before QWidget. It means style the QWidget, but exclude the subclasses. This is necessary because QPushButton is a subclass of QWidget and otherwise would be affected as well.
Then you can set the pushButton's backgroung color to transparent as you do with
ui->pushButton->setStyleSheet("QPushButton{background: transparent;}");
Example
Here is a simple example I have prepared for you in order to demonstrate the proposed solution (requires cat.png in the resource file under pix/images):
#include <QMainWindow>
#include <QWidget>
#include <QPushButton>
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = nullptr) :
QMainWindow(parent) {
auto *widget = new QWidget(this);
auto *button = new QPushButton(widget);
widget->setStyleSheet(".QWidget {"
" background-image:url(':/pix/images/cat.png');"
" background-repeat: no-repeat;"
"}");
button->setStyleSheet(".QPushButton {"
" background-color: transparent"
"}");
button->move(100, 100);
button->resize(100, 100);
connect(button, &QPushButton::clicked, [](){
qDebug("clicked");
});
setCentralWidget(widget);
resize(600, 480);
}
};
Result
The given example produces a window with a background and a 100x100px invisible clickable area positioned at (100, 100):
I think it's better to answer here than in comments.
You just have to set the following stylesheet for your QPushButton to make it invisible:
QPushButton
{
border: none;
}
I've made the test and it worked well.
For the tests, I have set the wrapping widget's background-image property. I also did another test with the background-color property instead. It worked in both cases (whether the background is a plain color or a picture/photo).
I hope it helps.
EDIT:
I have written a widget that performs what you want. And I also provided a windows in order to make the below example minimal and complete so that you can reproduce it.
I have tested it and it worked well.
test.h:
#ifndef TEST_H
#define TEST_H
#include <QMainWindow>
#include <QPushButton>
class WidgetWithHiddenButton : public QWidget
{
Q_OBJECT
protected:
QPushButton * invisible_button;
public:
WidgetWithHiddenButton(QWidget * parent = nullptr);
QPushButton * getButton();
protected:
void paintEvent(QPaintEvent *) override;
};
class TestWindow final : public QMainWindow
{
Q_OBJECT
private:
WidgetWithHiddenButton * widget;
public:
TestWindow();
};
#endif // TEST_H
test.cpp:
#include "test.h"
#include <QApplication>
#include <QStyleOption>
#include <QPainter>
#include <QVBoxLayout>
WidgetWithHiddenButton::WidgetWithHiddenButton(QWidget * parent) : QWidget(parent)
{
// build your widget as you want.
invisible_button = new QPushButton("Here is a button", this);
QVBoxLayout * lay = new QVBoxLayout;
QHBoxLayout * inner_lay = new QHBoxLayout;
inner_lay->addStretch();
inner_lay->addWidget(invisible_button);
inner_lay->addStretch();
lay->addLayout(inner_lay);
this->setLayout(lay);
this->setStyleSheet("WidgetWithHiddenButton {background-image: url(path_to_image/image.jpg);}");
invisible_button->setStyleSheet("QPushButton {border: none;}");
}
QPushButton * WidgetWithHiddenButton::getButton()
{
return invisible_button;
}
void WidgetWithHiddenButton::paintEvent(QPaintEvent *)
{
QStyleOption opt;
opt.init(this);
QPainter p(this);
style()->drawPrimitive(QStyle::PE_Widget, &opt, &p, this);
}
TestWindow::TestWindow()
{
resize(500, 300);
widget = new WidgetWithHiddenButton;
this->setCentralWidget(widget);
connect(widget->getButton(), &QPushButton::clicked, qApp, &QApplication::quit);
}
int main(int argc, char ** argv)
{
QApplication app(argc, argv);
TestWindow tw;
tw.show();
return app.exec();
}
Feel free to adapt it (especially by changing the class name because WidgetWithHiddenButton is very ugly :) ).
Notes:
I have written a text in the button in order to make it visible (for tests purposes) but you can remove it if you want the button completely invisible.
I connected the QPushButton::clicked() signal to the QApplication::quit() slot in order to perform an action when we click on the area of the button.
I redefined the paintEvent() method because it is needed when using Q_OBJECT macro alongside stylesheets over a custom QWidget as the documentation mentioned.
Feel free to modify the way I build the widget in the constructor (layouts, sizes, ...) to make it fit your requirements.
I have this very strange issue regarding a QMenu and its position when execing.
Here is the code for my subclassed QMenu:
DockItemContextMenu::DockItemContextMenu(QWidget *parent) : QMenu(parent){
style = qApp->style();
QPointer<QAction> restoreAction = new QAction(QIcon(style->standardIcon(QStyle::SP_TitleBarMaxButton)), "Restore", this);
QPointer<QAction> minimizeAction = new QAction(style->standardIcon(QStyle::SP_TitleBarMinButton), "Minimize", this);
QPointer<QAction> maximizeAction = new QAction(style->standardIcon(QStyle::SP_TitleBarMaxButton), "Maximize", this);
QPointer<QAction> stayOnTopAction = new QAction("Stay On Top", this);
stayOnTopAction->setCheckable(true);
QPointer<QAction> closeAction = new QAction(style->standardIcon(QStyle::SP_TitleBarCloseButton), "Close", this);
this->addActions({restoreAction, minimizeAction, maximizeAction, stayOnTopAction, closeAction});
connect(restoreAction, &QAction::triggered, parent, [this](){ emit restoreTriggered();}, Qt::QueuedConnection);
connect(minimizeAction, &QAction::triggered, parent, [this](){ emit minimizeTriggered();}, Qt::QueuedConnection);
connect(maximizeAction, &QAction::triggered, parent, [this](){ emit maximizeTriggered();}, Qt::QueuedConnection);
connect(stayOnTopAction, &QAction::triggered, parent, [this](){ emit stayOnTopTriggered();}, Qt::QueuedConnection);
connect(closeAction, &QAction::triggered, parent, [this](){ emit closeTriggered();}, Qt::QueuedConnection);
}
Okay, so essentially I have another widget who holds an instance of this DockItemContextMenu as a field. In this owning class, called Titlebar, I made it such that doing a right click will emit the customContextMenuRequested(QPoint) signal.
TitleBar::TitleBar(QString title, QWidget *parent){
...
this->setContextMenuPolicy(Qt::CustomContextMenu);
contextMenu = new DockItemContextMenu(this);
connect(this, SIGNAL(customContextMenuRequested(QPoint)), this, SLOT(showContextMenu(QPoint)), Qt::QueuedConnection);
...
}
After this, this widget is essentially inserted into a QGraphicsScene and is converted implicitly into a QGraphicsItem. When I do the FIRST right click event on my Titlebar it will not exec at the correct screen position if I dragged the MainWindow of the entire QApplication anywhere other than its starting position on screen. In addition to being in a QGraphicsScene, this scene itself is always stored in a QSplitter. Now I would understand if this always had some sort of issue, but it turns out, every time I call the slot for that signal, ONLY the first time will it exec in the incorrect position in the QGraphicsScene. No matter how I manipulate the size of the Titlebar widget itself, move commands or maximize commands to the MainWindow, or even edit the splitter size for the QGraphicsView that affects the size of the QGraphicsScene, it will always be in the correct position afterwards. here is the function for execing:
void TitleBar::showContextMenu(QPoint point){
qDebug() << point;
contextMenu->exec(point);
emit _parent->focusChangedIn();
}
I printed the point at which it is calling the exec. The strangest part is that both times I right click in the same location, it will print the SAME value for the slot's positional parameter both the first exec and second exec, but be in the correct location every time other than the first. Did I forget to set some other flag when I added the context menu to the Titlebar class? Does it have anything to do with setting the QMenu's parent to the Titlebar? I'm just dumbfounded how the same QPoint could exec at two different screen locations given the same value. Does anybody have a clue what may or may not be happening on the first call to the Titlebar's slot for execing the QMenu?
EDIT: The issue stemmed from doing this line of code in the Titlebar constructor:
contextMenu = new DockItemContextMenu(this);
Changing it to:
contextMenu = new DockItemContextMenu;
fixed the issue. Does anyone know why, or is this possibly a bug? I rather not accept this as an answer because it does not explain why it happened in the first place.
Here is a minimal example with the same effect.
MainWindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QWidget>
#include <QGraphicsView>
#include <QSplitter>
#include <QHBoxLayout>
#include <QGraphicsScene>
#include <QPointer>
#include <QTreeWidget>
#include "titlebar.h"
class MainWindow : public QMainWindow{
Q_OBJECT
public:
MainWindow(QWidget *parent = 0);
~MainWindow();
private:
};
#endif // MAINWINDOW_H
MainWindow.cpp:
#include "mainwindow.h"
MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent){
QPointer<QWidget> widgetArea = new QWidget;
QPointer<QHBoxLayout> hLayout = new QHBoxLayout;
widgetArea->setLayout(hLayout);
QPointer<QSplitter> splitter = new QSplitter;
hLayout->addWidget(splitter);
QPointer<QTreeView> tree = new QTreeView;
splitter->addWidget(tree);
QPointer<QGraphicsView> view = new QGraphicsView;
splitter->addWidget(view);
splitter->setStretchFactor(0, 1);
splitter->setStretchFactor(1, 4);
QPointer<QGraphicsScene> scene = new QGraphicsScene;
view->setScene(scene);
QPointer<Titlebar> blue = new Titlebar;
blue->setObjectName("blue");
blue->setStyleSheet(QString("#blue{background-color: rgb(0,0,255)}"));
blue->resize(250,250);
scene->addWidget(blue);
this->setCentralWidget(widgetArea);
this->resize(1000,750);
}
MainWindow::~MainWindow(){
}
Titlebar.h:
#ifndef TITLEBAR_H
#define TITLEBAR_H
#include <QMenu>
#include <QWidget>
#include <QPointer>
#include <QDebug>
#include <QMouseEvent>
class Titlebar : public QWidget{
Q_OBJECT
public:
explicit Titlebar(QWidget *parent = nullptr);
QPointer<QMenu> menu;
QPoint currentPos;
protected slots:
void mousePressEvent(QMouseEvent* event);
void mouseMoveEvent(QMouseEvent* event);
void showContextMenu(QPoint point);
};
#endif // TITLEBAR_H
Titlebar.cpp:
#include "titlebar.h"
Titlebar::Titlebar(QWidget *parent) : QWidget(parent){
setContextMenuPolicy(Qt::CustomContextMenu);
connect(this, SIGNAL(customContextMenuRequested(QPoint)), this, SLOT(showContextMenu(QPoint)), Qt::QueuedConnection);
menu = new QMenu(this);
menu->addAction("Test");
}
void Titlebar::showContextMenu(QPoint point){
qDebug() << point;
menu->exec(mapToGlobal(point));
}
void Titlebar::mouseMoveEvent(QMouseEvent *event){
if (event->buttons() && Qt::LeftButton){
QPoint diff = event->pos() - currentPos;
move(pos() + diff);
}
}
void Titlebar::mousePressEvent(QMouseEvent * event){
currentPos = event->pos();
}
main.cpp:
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
So this runs and reproduces the error accordingly. If you change the line in Titlebar.cpp from
menu = new QMenu(this);
to:
menu = new QMenu;
Then it works correctly. ONLY the first right click to open the context menu will spawn in the incorrect location on screen. All subsequent right clicks will now follow either the widget/window/splitter in any combination. I don't get it, can someone tell me if this is actually a bug or not.
You need to add one line of code because your using a QGraphicsProxyWidget which is part of a QGraphicsScene. The scene is represented by a QGraphicsView which inherits QAbstractScrollArea. This causes the context menu to be shown via the viewport and not the widget itself. Therefore adding this one line of code will override the title bar to not be embedded in the scene when it's parent was already embedded in the scene. Effectively making it reference the widget again and not the viewport.
In the MainWindow.cpp right after line 26 add
blue->setWindowFlags(Qt::BypassGraphicsProxyWidget);
I've created a Graphics View object in my mainwindow.ui file and I'm trying to display an image in that. For TextBrowser objects, I was doing like this
QTextBrowser *textBrowser_Actors = this->findChild<QTextBrowser*>("textBrowser_Actors");
textBrowser_Actors->setText(QString::fromUtf8(movie.get_actors().c_str()));
Similar way, how do I set an image after finding a GraphicsView by the below method?
QGraphicsView* movie_poster = this->findChild<QGraphicsView*>("movie_poster");
I tried the following from googling a bit, but couldn't get it working so far.
QGraphicsScene* scene = new QGraphicsScene();
movie_poster->setScene(scene);
QGraphicsPixmapItem* item = new QGraphicsPixmapItem(QPixmap::fromImage("movie.jpg"));
scene->addItem(item);
movie_poster->show();
Edit-1
int main(int argc, char *argv[])
{
std::vector<Movie> movie_vector; // This is where movie DB will be read to, and new movies will be added to
MainWindow w;
w.setWindow(movie_vector[0]); // calling setWindow with first movie
w.show();
return a.exec();
}
//setWindow definition
void MainWindow::setWindow(Movie &movie) {
// Next two lines gets the textBrowser object and set its value to movie title
QTextBrowser *textBrowser_Title = this->findChild<QTextBrowser*>("textBrowser_Title");
textBrowser_Title->setText(QString::fromUtf8(movie.get_title().c_str()));
// This is where I'm trying to get GraphicsView object and set an image in it.
QGraphicsView* movie_poster = this->findChild<QGraphicsView*>("movie_poster");
QGraphicsScene* scene = new QGraphicsScene();
movie_poster->setScene(scene);
QGraphicsPixmapItem* item = new QGraphicsPixmapItem(QPixmap("C:\Users\Name\Desktop\codes\Qt\MovieDB\titanic.jpg"));
scene->addItem(item);
movie_poster->show();
}
Maybe this answer help you: https://stackoverflow.com/a/7138147/6631835
this is my code:
#include "mainwindow.h"
#include <QGraphicsView>
#include <QPixmap>
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
{
resize(800,800);
this->image=new QImage();
openImage();
}
void MainWindow::openImage(){
image->load("/home/ztftrue/Downloads/test.jpg");
QGraphicsScene* scene=new QGraphicsScene() ;
QGraphicsView* view = new QGraphicsView(scene);
QGraphicsPixmapItem* item = new QGraphicsPixmapItem(QPixmap::fromImage(*image));
scene->addItem(item);
view->show();
}
MainWindow::~MainWindow()
{
}
I have the following code to set up a QGraphicsScene. I wish to click on the scene and draw a point at the location I've clicked. How could I do this? This is my current code:
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QGraphicsScene *scene;
QGraphicsView *view = new QGraphicsView(this);
view->setGeometry(QRect(20, 50, 400, 400));
scene = new QGraphicsScene(50, 50, 350, 350);
view->setScene(scene);
}
UPDATE: There is a new class called QGraphicsSceneMouseEvent that makes this a little easier.
I just finished an example using it here:
https://stackoverflow.com/a/26903599/999943
It differs with the answer below in that it subclasses QGraphicsScene, not QGraphicsView, and it uses mouseEvent->scenePos() so there isn't a need to manually map coordinates.
You are on the right track, but you still have a little more to go.
You need to subclass QGraphicsView to be able to do something with mouse presses or with mouse releases using QMouseEvent.
#include <QGraphicsView>
#include <QGraphicsScene>
#include <QGraphicsEllipseItem>
#include <QMouseEvent>
class MyQGraphicsView : public QGraphicsView
{
Q_OBJECT
public:
explicit MyQGraphicsView(QWidget *parent = 0);
signals:
public slots:
void mousePressEvent(QMouseEvent * e);
// void mouseReleaseEvent(QMouseEvent * e);
// void mouseDoubleClickEvent(QMouseEvent * e);
// void mouseMoveEvent(QMouseEvent * e);
private:
QGraphicsScene * scene;
};
QGraphicsView doesn't natively have dimension-less points. You will probably want to use QGraphicsEllipse item or simply, scene->addEllipseItem() with a very small radius.
#include "myqgraphicsview.h"
#include <QPointF>
MyQGraphicsView::MyQGraphicsView(QWidget *parent) :
QGraphicsView(parent)
{
scene = new QGraphicsScene();
this->setSceneRect(50, 50, 350, 350);
this->setScene(scene);
}
void MyQGraphicsView::mousePressEvent(QMouseEvent * e)
{
double rad = 1;
QPointF pt = mapToScene(e->pos());
scene->addEllipse(pt.x()-rad, pt.y()-rad, rad*2.0, rad*2.0,
QPen(), QBrush(Qt::SolidPattern));
}
Note the usage of mapToScene() to make the pos() of the event map correctly to where the mouse is clicked on the scene.
You need to add an instance of your subclassed QGraphicsView to the centralWidget's layout of your ui if you are going to use a form.
QGridLayout * gridLayout = new QGridLayout(ui->centralWidget);
gridLayout->addWidget( new MyQGraphicsView() );
or if your ui has a layout already it will look like this:
ui->centralWidget->layout()->addWidget( new MyGraphicsView() );
If you don't use a QMainWindow and a form, you can add it to a QWidget if you set a layout for it and then add your QGraphicsView to that layout in a similar manner. If you don't want a margin around your QGraphicsView, just call show on it and don't put it inside a different layout.
#include <QtGui/QApplication>
#include "myqgraphicsview.h"
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MyQGraphicsView view;
view.show();
return a.exec();
}
And that's it. Now you are dangerous with QGraphicsView's and their interaction with the mouse.
Be sure to read and study about Qt's Graphics View Framework and the related examples to be effective when using QGraphicsView and QGraphicsScene. They are very powerful tools for 2D graphics and can have a bit of a learning curve but they are worth it.