29 基本绘图操作

绘图事件：void paintEvent(QPaintEvent *);

 展示：

 代码

//widget.h
#ifndef WIDGET_H
#define WIDGET_H

#include 

namespace Ui {
class Widget;
}

class Widget : public QWidget
{
    Q_OBJECT

public:
    explicit Widget(QWidget *parent = 0);
    ~Widget();

    void paintEvent(QPaintEvent *);

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

//widget.cpp
#include "widget.h"
#include "ui_widget.h"
#include "QPainter"

Widget::Widget(QWidget *parent) :
    QWidget(parent),
    ui(new Ui::Widget)
{
    ui->setupUi(this);
}

//重写绘图事件
void Widget::paintEvent(QPaintEvent *){
    QPainter painter(this); //this指代绘图设备，画家想当前窗口绘图

    //画笔
    QPen pen(QColor(255,0,0));

    //设置画笔宽度
    pen.setWidth(3);

    //设置画笔风格
    pen.setStyle(Qt::DotLine);

    //画家使用画笔
    painter.setPen(pen);

    //画刷 可以 填充封闭的图案
    QBrush brush(Qt::cyan);

    //设置画刷风格
    brush.setStyle(Qt::CrossPattern);

    //画家使用画刷
    painter.setBrush(brush);

    //画线
    painter.drawLine(QPoint(0,0),QPoint(100,100));

    //画圆
    painter.drawEllipse(QPoint(100,100),50,50);//center x y

    //画矩形
    painter.drawRect(QRect(20,20,50,50)); //x y w h

    //画字
    painter.setFont(QFont("华文彩云",20));
    painter.drawText(QRect(0,200,150,100),"好好学习，天天向上");

}

Widget::~Widget()
{
    delete ui;
}