[Solved] Draw lines animation

ZsCosa

!http://i.stack.imgur.com/TQnIx.gif(Draw Line Animation)!
Hi, I'm trying to create a drawing animation similar to the above, where it literally is drawing a line like using a pen. I've read the QAnimationFramework and at the moment I'm currently working on a solution by changing the coordinate of the QLineF by inherting QGraphicsLineItem to QObject then use QPropertyAnimation to animate it.
I'm a newbie so wondering if this is possible, or if you can suggest a direction for me would be awesome. Thanks very much!

ZsCosa

So I went with a QTimer approach, by connect timeout() with a slot called move() where it gradually increase the end point of the line:
myLine.h
@#ifndef MYLINE_H
#define MYLINE_H

#include <QGraphicsLineItem>

class myLine : public QObject, public QGraphicsLineItem
{
Q_OBJECT

public:
myLine();
QRectF boundingRect();
void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);

private slots:
void mySlot();
private:
QLineF thisline;

};
#endif // MYLINE_H
@
myLine.cpp
@#include "myLine.h"

#include <QPainter>
#include <QApplication>

myLine::myLine()
{
thisline.setLine(0,0,50,50);
}

QRectF myLine::boundingRect()
{
return QRectF(0,0,500,500);
}

void myLine::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
painter->setRenderHint(QPainter::Antialiasing);
painter->setPen(QPen(Qt::red, 8, Qt::SolidLine, Qt::RoundCap, Qt::MiterJoin));
painter->setBrush(QBrush(Qt::white, Qt::DiagCrossPattern));
painter->drawRect(boundingRect());
painter->drawLine(thisline);
}

void myLine::mySlot()
{
for (int i = 1; i < 100; i++)
{
QLineF line = this->line();
line.setLine(0,0,50+i,50+i);
update();
qApp->processEvents();
}

}
@
and main.cpp
@ scene = new QGraphicsScene(this);

ui->graphicsView->setScene(scene);
ui->graphicsView->setSceneRect(0,0,700,700);
ui->graphicsView->setRenderHint(QPainter::Antialiasing);

myLine *line = new myLine();
scene->addItem(line);

timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), line, SLOT(mySlot()));
timer->start(100);@

However it only draw a single line, there was no animation. I think there's a problem in the loop or SLOT so i would be very grateful can point this out for me. Thannks very much!

SGaist

Hi and welcome to devnet,

You should not have a for loop in your slot rather each time your slot is called you increment your line coordinates and call update(). Also in your slot you are modifying a copy of the line without setting it after.

If I've read the documentation correctly you shouldn't even need to sub class QGraphicsLineItem. Just use it

Hope it helps

ZsCosa

Hi, thanks very much for your reply.

Yes you're right, I didn't have to subclass QgraphicsLineItem so I removed it then use QPropertyAnimation to modifies the endpoint coordinate of the line and that does the job.

Cheers,

SGaist

You're welcome !

Please update the thread's title to solved so other forum users may know a solution has been found :)