How to move an item on a GraphicsScene

[Holy]

Hi,
II'm trying to move a GraphicsItem on a GraphicsScene using moveBy()Function but nothing moves on the screen , may someone help me to achieve this ?
Thanks in advance
here is the Programmcode i tried to write :
-------

class Container: public QGraphicsRectItem
{
public:
Container(QGraphicsItem* parent=0, intx, int y);
};
Container::Container(QGraphicsItem* parent, intx=0, int y=0): QGraphicsRectItem(parent)
{QColor color (0,0,100);
QPen p(color);
p.setWidth(2);
QBrush brush(QColor(0,160,0));
setPen(p);
setBrush(brush);
setRect()x,y,100,60;
show();
}

class Container: public QGraphicsRectItem
{
public:
Container(QGraphicsItem* parent=0, intx, int y);
};
Container::Container(QGraphicsItem* parent, intx=0, int y=0): QGraphicsRectItem(parent)
{QColor color (0,0,100);
QPen p(color);
p.setWidth(2);
QBrush brush(QColor(0,160,0));
setPen(p);
setBrush(brush);
setRect()x,y,100,60;
show();
}

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--------

#include"Container.h"
class Scene: public QGraphicsScene
{
public:
Scene(QWidget* parent=0);
Container*container;
};
Scene::Scene(QWidget* parent):QGraphicsScene(parent)
{
QBrush brush(QColor(180,180,220), Qt::Dense4Pattern);
setBackgroundBrush(brush);
}

#include"Container.h"
class Scene: public QGraphicsScene
{
public:
Scene(QWidget* parent=0);
Container*container;
};
Scene::Scene(QWidget* parent):QGraphicsScene(parent)
{
QBrush brush(QColor(180,180,220), Qt::Dense4Pattern);
setBackgroundBrush(brush);
}

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--------
mainGui class

#include"include/gui/mainGui.h"
#include"include/gui/Scene.h"
#include"include/gui/container.h"
class MainGui:public QWidget
{
Q_OBJECT
public:
MainGui(QWidget*parent=0);
private:
QGraphicsScene *scene;
};
MainGui::MainGui(QWidget *parent):QWidget(parent)
{
scene=newScene(this);
Container*c1= new Container(0,0,0);
// I want the item to move step by step after any 1000 ms on the Screen
QMoveEvent *event;
int x=event->pos().x();
int y=event->pos().y();
c1->moveBy((qreal)x,(qreal)y);
startTimer(1000);
c1->addItem(c1);
scene->addLine(-5, -200, -5, 200);
scene->addLine(105, -200,105, 200);
scene->advance();
QGraphicsView *view =new QGraphicsView (scene);
QGridLayout *layout= new QGridLayout();
layout->addWidget(view);
setLayou(layout);
view->show();
}

#include"include/gui/mainGui.h"
#include"include/gui/Scene.h"
#include"include/gui/container.h"
class MainGui:public QWidget
{
Q_OBJECT
public:
MainGui(QWidget*parent=0);
private:
QGraphicsScene *scene;
};
MainGui::MainGui(QWidget *parent):QWidget(parent)
{
scene=newScene(this);
Container*c1= new Container(0,0,0);
// I want the item to move step by step after any 1000 ms on the Screen
QMoveEvent *event;
int x=event->pos().x();
int y=event->pos().y();
c1->moveBy((qreal)x,(qreal)y);
startTimer(1000);
c1->addItem(c1);
scene->addLine(-5, -200, -5, 200);
scene->addLine(105, -200,105, 200);
scene->advance();
QGraphicsView *view =new QGraphicsView (scene);
QGridLayout *layout= new QGridLayout();
layout->addWidget(view);
setLayou(layout);
view->show();
}

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[jacek]

// I want the item to move step by step after any 1000 ms on the Screen
QMoveEvent *event;
int x=event->pos().x();
int y=event->pos().y();
c1->moveBy((qreal)x,(qreal)y);

It won't work --- you take x and y values from an uninitialized object.

startTimer(1000);

When you use startTimer(), you have to reimplement QObject::timerEvent() and put the code that you want to run every second there.

You need something like:

void MainGui::timerEvent( QTimerEvent *e )
{
   Q_UNUSED( e);
   scene->advance();
}

void MainGui::timerEvent( QTimerEvent *e )
{
   Q_UNUSED( e);
   scene->advance();
}

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You can also consider using QTimer instead of startTimer()/timerEvent().

To make scene->advance() work, you have to reimplement QGraphicsItem::advance() in your Container class or use QGraphicsItemAnimation.

P.S. Please, don't post the same question twice in two different threads.

[Holy]

hi,
Sorry for the posts and thanks for your answer.
i tried to do like you said namely:
------ MainGui.cpp

MainGui::MainGui(QWidget *parent): QWidget(parent)
{
...
}
void MainGui::timerEvent(QTimerEvent *e)
	{
		Q_UNUSED(e);
 
	QGraphicsItemAnimation anim;
anim.setItem(c1);
 
for(int i=0; i<200; i++)
{
anim.yTranslationAt(i/200.0);
 
}
		scene->advance();
		update();
 
	}

MainGui::MainGui(QWidget *parent): QWidget(parent)
{
...
}
void MainGui::timerEvent(QTimerEvent *e)
	{
		Q_UNUSED(e);

	QGraphicsItemAnimation anim;
anim.setItem(c1);

for(int i=0; i<200; i++)
{
anim.yTranslationAt(i/200.0);

}
		scene->advance();
		update();
		
	}

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but it doesn't work.
I also tried like this:

MainGui::MainGui(QWidget *parent): QWidget(parent)
{
 
	//QWidget *myWidget= new QWidget();
 
	scene = new Scene(this);
 
	Container *c1 = new Container(0, 0, 0);
 
QGraphicsItemAnimation anim;
QTimeLine *timeline = new QTimeLine(5000);
anim.setItem(c1);
for(qreal i=0.0;i<200.0;i++)
{
anim.setTranslationAt(i/200.0,i,i);
anim.yTranslationAt(i/200.0);
 
}
 
anim.setTimeLine(timeline);
timeline->setUpdateInterval(1000/3);
timeline->setLoopCount(0);
timeline->setDuration(5000);
timeline->start();
 
}

MainGui::MainGui(QWidget *parent): QWidget(parent)
{
	
	//QWidget *myWidget= new QWidget();

	scene = new Scene(this);
	
	Container *c1 = new Container(0, 0, 0);
	
QGraphicsItemAnimation anim;
QTimeLine *timeline = new QTimeLine(5000);
anim.setItem(c1);
for(qreal i=0.0;i<200.0;i++)
{
anim.setTranslationAt(i/200.0,i,i);
anim.yTranslationAt(i/200.0);

}

anim.setTimeLine(timeline);
timeline->setUpdateInterval(1000/3);
timeline->setLoopCount(0);
timeline->setDuration(5000);
timeline->start();

}

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the item doesn't move as well, please can you write it in the right way so that it can work?
thanks in advance

[jacek]

You create the animation object on the stack and it gets destroyed as soon as the constructor ends. Make it a member variable.

[Holy]

I did it, but there's no change, nothing moves.

can someone post me an example that works please?
what i want is to move the item upper in the vertical direction.
thanks for help.

[Holy]

it works now! thanks very much for the last idea!
but there's another problem, the item is moving down. How can i get it moving up first and then moving down and the movement should be inside the lines (i mean the item should remain inside the lines when moving) .
thanks for your help.

[jacek]

but there's another problem, the item is moving down. How can i get it moving up first and then moving down and the movement should be inside the lines

The movement is controlled by the animation object:

for( int i = 0; i < 50; ++i ) {
   anim.setTranslationAt( i / 100.0, 0, i );
}
for( int i = 50; i < 100; ++i ) {
   anim.setTranslationAt( i / 100.0, 0, 50 - i );
}

for( int i = 0; i < 50; ++i ) {
   anim.setTranslationAt( i / 100.0, 0, i );
}
for( int i = 50; i < 100; ++i ) {
   anim.setTranslationAt( i / 100.0, 0, 50 - i );
}

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[Holy]

thanks for your reply;
i have another problem , while inserting items in the scene all items are added at the same time but not one after another like i want them to be added, i've tried to controll this adding action of the scene by controlling the QTimeLine of Container :

something like this:
the variable QTimeLine timeline is declared public in the class container; i use it to controll the animation of the containers.

void MainGui::addnextContainer(int i, QGraphicsScene *scene1)
{
for(int i=0;i<containerNum; i++)
{
Container*[i];
scene1->addItem(c[i]);
c[i]->timeline->start();
c[i+1]->timeline->setPaused(true);
l_items(c[i]);
c[i]->timeline->stop();
scene1->addItem(c[i+1]);
c[i+1]->timeline->start();
l_items()
 
}
}

void MainGui::addnextContainer(int i, QGraphicsScene *scene1)
{
for(int i=0;i<containerNum; i++)
{
Container*[i];
scene1->addItem(c[i]);
c[i]->timeline->start();
c[i+1]->timeline->setPaused(true);
l_items(c[i]);
c[i]->timeline->stop();
scene1->addItem(c[i+1]);
c[i+1]->timeline->start();
l_items()

}
}

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puting the items in a range in the scene

QList<QGraphicsItem*>MainGui:: l_items(QGraphicsItem *item1)
{
QList<QGraphicsItem*>listing=scene->items();
listing.clear();
for(int i=0; i<listing.size();i++)
{
listing.append(item1);
 
}
return listing;
}

QList<QGraphicsItem*>MainGui:: l_items(QGraphicsItem *item1)
{
QList<QGraphicsItem*>listing=scene->items();
listing.clear();
for(int i=0; i<listing.size();i++)
{
listing.append(item1);

}
return listing;
}

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and i changed the MainGui.cpp

...
Scene scene= new Scene(this);
addnextContainer(5, scene)
...

...
Scene scene= new Scene(this);
addnextContainer(5, scene)
...

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can someone take a look at this code and tell me please what i'm doing wrong please? now i even cannot see any item anymore.
thanks in advance

[jacek]

What is l_items() method supposed to do? Now it just returns an empty list.

[Holy]

apology for the late reply, i did something else as i didn't get the solution of this problem.
back to your question.
the l_items() method is supposed to list the containers objects which are added to the scene. Can you also help me by controlling the addItem() method so that the containers should be added one by one and not all at the same time?
thanks in advance.

[jacek]

the l_items() method is supposed to list the containers objects which are added to the scene.

Lines 5--9 are never executed because you clear the list in line 4.

Can you also help me by controlling the addItem() method so that the containers should be added one by one and not all at the same time?

What do you mean by "one by one"? Do you want to have some kind of animation?