从'QEvent *'到'QPaintEvent *'的无效转换

时间:2011-06-13 12:08:59

标签: qt events qt4 qpainter touch-event

尝试查找触摸事件是否发生,或者只是绘制它们。


bool MyWidget::event(QEvent *event)
{
    switch (event->type())
    {
            case QEvent::TouchBegin:
            case QEvent::TouchUpdate:
            case QEvent::TouchEnd: 
        {

            QTouchEvent *touchEvent = static_cast(event);

            if (touchEvent->touchPoints().count() == 2) 
            {
                const QTouchEvent::TouchPoint &touchPoint1 = touchEvent->touchPoints().first();
                const QTouchEvent::TouchPoint &touchPoint2 = touchEvent->touchPoints().last();
                nx=touchPoint1.scenePos().x();
                ny=touchPoint1.scenePos().y();
                pix = QPixmap::grabWidget (this,nx,ny,1,1);
                img = pix.toImage();
                rgb = img.pixel(0,0);
                color.setRgb(rgb);
                drawBit=1;
            }
        break;
         }

            case QEvent::Paint:

                  return MyWidget::paintEvent( event);  
              break;

         default:
            return false;
            break;
    }

     return true;
}



void MyWidget::paintEvent(QPaintEvent *event)
{

time_counter++;
for(i=0;(ired,b[i]->green,b[i]->blue,255), Qt::SolidPattern));
painter.drawEllipse(b[i]->x,b[i]->y,b[i]->w, b[i]->w);
painter.drawLine(b[i]->x+b[i]->w/2,b[i]->y+b[i]->w,b[i]->x+b[i]->w/2,b[i]->y+2*b[i]->w);

if(b[i]->ballDead==false)
b[i]->y+=b[i]->vy;

if(drawBit==1 && b[i]->red==color.red() && b[i]->green==color.green() && b[i]->blue==color.blue())
ballHit(i);


}
}



this code shows error like:
mywidget.cpp:116:47: error: invalid conversion from ‘QEvent*’ to ‘QPaintEvent*’
mywidget.cpp:116:47: error:   initializing argument 1 of ‘virtual void MyWidget::paintEvent(QPaintEvent*)’
mywidget.cpp:116:47: error: void value not ignored as it ought to be

2 个答案:

答案 0 :(得分:3)

直接调用paintEvent()不是一个好习惯。请调用repaint()update()。然后这些方法会使用正确的参数调用paintEvent()

答案 1 :(得分:3)

如果您想致电paintEvent,则需要投放QEvent*,例如:

paintEvent(static_cast<QPaintEvent*>(event));
return true;

但是正如其他人所说的那样,如果你发现自己处于无休止的重复循环或者其他事件循环中,请不要抱怨。

如果您想要定期重新绘制,请设置QTimer并让它调用小部件的update()广告位。