Qt 使用QGraphicsItem绘制复杂的图形

程序运行截图如下：

原理：使用QPainter一个部分，一个部分的画

源码：

mygraphicsitem.h

ifndef MYGRAPHICSITEM_H
#define MYGRAPHICSITEM_H
 
#include <QGraphicsItem>
 
class MyGraphicsItem:public QGraphicsItem
{
public:
    MyGraphicsItem(QGraphicsItem *parent=0);
    ~MyGraphicsItem();
 
protected:
    QRectF boundingRect()const;
    void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
};
 
#endif // MYGRAPHICSITEM_H

widget.h

#ifndef WIDGET_H
#define WIDGET_H
 
#include <QWidget>
class QGraphicsScene;
 
namespace Ui {
class Widget;
}
 
class Widget : public QWidget
{
    Q_OBJECT
 
public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();
 
private:
    Ui::Widget *ui;
    QGraphicsScene *m_scene;
};
 
#endif // WIDGET_H

main.cpp

#include "widget.h"
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
 
    return a.exec();
}

mygraphicsitem.cpp

#include "mygraphicsitem.h"
#include <QPainter>
#include <QPen>
#include <QRectF>
 
MyGraphicsItem::MyGraphicsItem(QGraphicsItem *parent):
    QGraphicsItem(parent)
{
    setFlags(QGraphicsItem::ItemIsSelectable|QGraphicsItem::ItemIsMovable);
}
 
MyGraphicsItem::~MyGraphicsItem()
{
 
}
 
QRectF MyGraphicsItem::boundingRect() const
{
    return QRectF(-14,-50,55,70);
}
 
void MyGraphicsItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(option)
    Q_UNUSED(widget)
    painter->setPen(QPen(Qt::white,1));
    painter->drawRect(-14,-50,55,70);
    painter->setPen(QPen(Qt::red,2));
    painter->drawLine(0,0,0,10);
    painter->drawLine(0,10,30,10);
    painter->drawLine(30,10,30,0);
    painter->drawLine(15,10,15,-20);
    painter->drawLine(15,-20,0,-20);
    QRectF rectangle(0,-33,30,30);
    int startAngle=-180*16;
    int spanAngle=270*16;
    painter->drawArc(rectangle, startAngle, spanAngle);
    painter->drawLine(15,-35,15,-40);
}

widget.cpp

#include "widget.h"
#include "ui_widget.h"
#include "mygraphicsitem.h"
#include <QGraphicsScene>
 
Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
    m_scene=new QGraphicsScene;
    ui->graphicsView->setScene(m_scene);
    ui->graphicsView->setRenderHint(QPainter::Antialiasing);
    m_scene->setBackgroundBrush(QBrush(Qt::black));
    MyGraphicsItem *item=new MyGraphicsItem;
    item->setPos(0,0);
    m_scene->addItem(item);
}
 
Widget::~Widget()
{
    delete ui;
}