Why doesn't the line appear on my Image?

[Gh0stR1der]

Hi everybody out there using Qt4, I am doing a simple experiment using Qt4, I just wanna draw lines on a loaded image, here's the paintEvent code:

void GpsLocator::paintEvent(QPaintEvent *event){
    image=new QImage();
    image->load(*imageName);
    windowPainter=new QPainter(this);
    windowPainter->initFrom(this);
    windowPainter->drawImage(0,0,*image);
    this->setMinimumSize(image->width(),image->height());
    imagePainter=new QPainter(image);
    imagePainter->setPen(QPen(Qt::DotLine));
    imagePainter->drawLine(218,223,433,375);
}

void GpsLocator::paintEvent(QPaintEvent *event){
    image=new QImage();
    image->load(*imageName);
    windowPainter=new QPainter(this);
    windowPainter->initFrom(this);
    windowPainter->drawImage(0,0,*image);
    this->setMinimumSize(image->width(),image->height());
    imagePainter=new QPainter(image);
    imagePainter->setPen(QPen(Qt::DotLine));
    imagePainter->drawLine(218,223,433,375);
}

To copy to clipboard, switch view to plain text mode 

but this doesn't work, while the image is loaded successfully, but the line doesn't appear, I am just wondering how this could happen? Can anyone do me a favor, many thanks!

[wysota]

The code is all wrong. Do you by any chance come from the Java world? It looks you are used to having a garbage collector and allocating everything on the heap. Don't do that with QImage and QPainter. Furthermore don't put the code in paintEvent as it may be called without you knowing and it is crucial that it executes as fast as possible. Fix the errors and then we can continue.