QGraphicsItem图形项

将QGraphicsView视图-优快云博客中的QGraphicsRectItem换成此类MyItem 。

//myitem.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QGraphicsItem>

class MyItem : public QGraphicsItem
{
public:
    MyItem();
    ~MyItem();
    QRectF boundingRect() const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
};
#endif // MAINWINDOW_H

//myitem.cpp

#include "myitem.h"
#include <QPainter>

MyItem::MyItem()
{
}

MyItem::~MyItem()
{
}

//用来返回要绘制图形项的矩形区域
//使用图形项坐标
QRectF MyItem::boundingRect() const
{
    qreal pen_width = 1;
    return QRectF(0 - pen_width / 2, 0 - pen_width / 2, 20 + pen_width, 20 + pen_width);
}

//用来执行实际的绘图操作
void MyItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    painter->setBrush(Qt::red);
    painter->drawRect(0, 0, 350, 20);
}