Delay in the output

? Offline

Hello,

im start today with the concept of QT.

My first aim is to create a grid. This work fine.

My Code is:

@
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);

QBrush greenBrush(Qt::green);
QBrush blueBrush(Qt::blue);
QPen outlinePen(Qt::black);
//outlinePen.setWidth(1);



//rectangle = scene->addRect( 0, 0, 5, 5, outlinePen, blueBrush);


for(int i = 0;i <= 500; i = i +10){

    for(int j = 0;j <= 500; j = j +10)
    {
        rectangle = scene->addRect( QRectF(i, j, 1, 1), outlinePen, blueBrush);
    }

}

}
@

My problem is to get every rectangle with a delay. For example 50 ms.
With the system function sleep, the application stucks.

How i could solve the problem?

Thx Andre

Jeroentjehome

Hi,
sleep shouldn't be used at all within Qt. Even not with multithreading.
What you need is a timer of 50msec which will paint a new rectangle every time the timer expires. Check out the QTimer classes and connect a slot to the expired signal.

? Offline

Hello,

thx for response.

i have integrate a timer class into the project, but i cant connect the Timer with the draw function:

This is the code.

mytimer.h:

@
#ifndef MYTIMER_H
#define MYTIMER_H

#include <QTimer>

class MyTimer : public QObject
{
Q_OBJECT
public:
MyTimer();
QTimer *timer;

public slots:
void MyTimerSlot();
};

#endif // MYTIMER_H
@

mytimer.cpp
@
#include "mytimer.h"
#include <QDebug>

MyTimer::MyTimer()
{
// create a timer
timer = new QTimer(this);

// setup signal and slot
connect(timer, SIGNAL(timeout()),
      this, SLOT(MyTimerSlot()));

// msec
timer->start(1000);

}

void MyTimer::MyTimerSlot()
{
qDebug() << "Timer...";
}
@

mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsItem>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

private:
Ui::MainWindow *ui;

QGraphicsScene *scene;

QGraphicsRectItem *rectangle;

};

#endif // MAINWINDOW_H
@

mainwindow.cpp
@
#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);



QBrush greenBrush(Qt::green);
QBrush blueBrush(Qt::blue);
QPen outlinePen(Qt::black);
//outlinePen.setWidth(1);

//rectangle = scene->addRect( 0, 0, 5, 5, outlinePen, blueBrush);




for(int i = 0;i <= 500; i = i +10){

    for(int j = 0;j <= 500; j = j +10)
    {
        rectangle = scene->addRect( QRectF(i, j, 1, 1), outlinePen, blueBrush);
    }

}

/*
for(int j = 0;j <= 500; j = j +10)
{
rectangle = scene->addRect( QRectF(j, j, 1, 1), outlinePen, blueBrush);
}
*/
}

MainWindow::~MainWindow()
{
delete ui;
}
@

main.cpp
@
#include "mainwindow.h"
#include <QApplication>
#include "MyTimer.h"

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

MainWindow w;

w.show();

MyTimer timer;

return a.exec&#40;&#41;;

}
@

Does anyone have a suggestion?

Thx
Andre

? Offline

Hi,
i don't see any draw function in your code. Create separate draw function as a slot in MainWindow, and connect this slot with timeout() QTimer signal in main window construcrot. Also, you can see the Animation Framework in Qt examples. Good luck!

? Offline

Hi,

thx for help.

the animation for a diagonal line is running, this is the same like a single for loop.

Does I need a second timer, If I want to design a two dimensional "for loop" for drawing a grid?

The modification of the code ist:

mainwindow.h
@
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsScene>
#include <QGraphicsView>
#include <QGraphicsItem>

#include <QTimer>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();

QTimer *timer2;

public slots:
void draw();

public:
Ui::MainWindow *ui;

QGraphicsScene *scene;

QGraphicsRectItem *rectangle;

int i;

};

#endif // MAINWINDOW_H

@

mainwindow.cpp

@
#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);

scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);


timer2 = new QTimer(this);

// create a timer


i = 0;


connect(timer2, SIGNAL(timeout()), this, SLOT(draw()));
// msec
timer2->start(1000);

}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::draw()
{
QBrush greenBrush(Qt::green);
QBrush blueBrush(Qt::blue);
QPen outlinePen(Qt::black);

 /*
 for(int i = 0;i <= 500; i = i +10){

     for(int j = 0;j <= 500; j = j +10)
     {
         rectangle = scene->addRect( QRectF(i, j, 1, 1), outlinePen, blueBrush);
     }

 }
 */

 rectangle = scene->addRect( QRectF(i, i, 1, 1), outlinePen, blueBrush);
 i +=10;

 qDebug() << "Draw...";

}

@

main.cpp
@
#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
QApplication a(argc, argv);

MainWindow w;

w.show();

return a.exec&#40;&#41;;

}

@

? Offline

Hi,

i think one solution, to paint a grid is:

@

void MainWindow::draw()
{
QBrush greenBrush(Qt::green);
QBrush blueBrush(Qt::blue);
QPen outlinePen(Qt::black);

 /*
 for(int i = 0;i <= 500; i = i +10){

     for(int j = 0;j <= 500; j = j +10)
     {
         rectangle = scene->addRect( QRectF(i, j, 1, 1), outlinePen, blueBrush);
     }

 }
 */



 rectangle = scene->addRect( QRectF(i, j, 1, 1), outlinePen, blueBrush);



 i +=10;


 if (i % 500 == 0 )
 {
     j += 10;
     i = 0;
     z++;
 }

 qDebug() << "Draw...\n";
 qDebug() << i ;
 qDebug() << "\n";
 qDebug() << j ;
 qDebug() << "\n";

 if (z  == 50)
    timer2->stop();

}

@

but i dont think it is an elegant way.

Does someone has a better solution ?

Thx Andre