[SOLVED] Subclassing QWidget not working

guidupas

Hello all!

I need to subclass QWidget, but its not working. When I call the function desenhaFluxo(), it returns the error:
QWidget::paintEngine: Should no longer be called
QPainter::begin: Paint device returned engine == 0, type: 1
QPainter::setPen: Painter not active

How can I do that?

@
#include "fluxocaixawidget.h"

fluxoCaixaWidget::fluxoCaixaWidget(QWidget *parent) :
QWidget(parent)
{

}

void fluxoCaixaWidget::paintEvent(QPaintEvent *)
{
QPainter painter(this);

QPen caneta(Qt::black);
caneta.setWidth(4);
painter.setPen(caneta);



painter.drawLine(20, this->parentWidget()->height() / 2 - 20, this->parentWidget()->width()-40, this->parentWidget()->height() / 2 - 20);

}

void fluxoCaixaWidget::desenhaFluxo()
{
QPainter painter(this);

QPen caneta(Qt::black);
caneta.setWidth(4);
painter.setPen(caneta);

painter.drawLine(10,10,50,10);

}

@

sierdzio

Quoting from the documentation:
[quote]Each widget performs all painting operations from within its paintEvent() function. This is called whenever the widget needs to be redrawn, either as a result of some external change or when requested by the application.[/quote]

I hope the reason for your warnings is clear now.

guidupas

Thanks for the reply Sierdzio!

I got it. But how could I do draw other lines calling a function like the code above?

MuldeR

Re-implement paintEvent() and perform all required drawing operations in there. As the docs say, Qt will call that method whenever your Widget needs to be (re)drawn. Of course you can call sub-functions, like desenhaFluxo(), from there. Just do not call functions which perform painting operations directly!

guidupas

Worked fine after clean the project