14、绘制图形（QPainter）

效果

// 定义一个新的类
#ifndef PAINTERAREA_H
#define PAINTERAREA_H

#include <QObject>
#include <QWidget>

//QPen  画笔是基本的图形对象，绘制直线、曲线、多边形等形状
#include <QPen>
//QBrush 画刷是基本的图形对象，主要用于填充，比如矩形、多边形等形状
#include <QBrush>

#include <QPainter>

class PainterArea : public QWidget
{
    Q_OBJECT
public:
    explicit PainterArea(QWidget *parent = nullptr);

    // 绘制直线、长方形
    enum shape{Line,Rectangle};

    void setshape(shape);//次函数实现绘制形状
    void setPen(QPen);
    void setBrush(QBrush);

    void paintEvent(QPaintEvent *event); //重绘事件（本来就有的函数）
    void setFillrule(Qt::FillRule); //填充规则

signals:

public slots:

private:
    shape shp; //形状
    QPen pen;  //画笔
    QBrush qbrush; //画刷
    Qt::FillRule fillrle; //规则


public slots:
};

#endif // PAINTERAREA_H

//实现定的的新的类
#include "painterarea.h"

PainterArea::PainterArea(QWidget *parent) : QWidget(parent)
{
    //调色板来改变背景颜色
    setPalette(QPalette(Qt::blue));
    // 用于当前窗口是否需要绘制背景
    setAutoFillBackground(true);

    //设置最小尺寸
    setMinimumSize(400,400);

}

void PainterArea::setshape(shape sh){
    shp=sh;
    update();
}

void PainterArea::setPen(QPen sh)
{
    pen=sh;
    update();
}

void PainterArea::setBrush(QBrush sh)
{
    qbrush = sh;
    update();
}

void PainterArea::paintEvent(QPaintEvent *event)
{
    QPainter p(this);
    p.setPen(pen);
    p.setBrush(qbrush);

    QRect rect(55,110,290,180);

    switch (shp) {
    case Line://实现直线
        p.drawLine(rect.topLeft(),rect.bottomRight());
        break;
    case Rectangle:
        p.drawRect(rect);
        break;
    default:
        break;
    }
}

void PainterArea::setFillrule(Qt::FillRule rle)
{
    fillrle=rle;
    update();//重新绘制区域窗体
}

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include "painterarea.h"
#include <QLabel>
#include <QGridLayout>
#include <QComboBox>
//颜色
#include <QColorDialog>

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    PainterArea *labelshapeArea;
    QLabel *labelshap;
    QComboBox *comboboxShape;

    QGridLayout *glayout;

private slots:
    void dispShapeFunc(int);
};

#endif // WIDGET_H

#include "widget.h"
#include <QDebug>


Widget::Widget(QWidget *parent)
    : QWidget(parent)
{
    labelshapeArea=new PainterArea;

    glayout = new QGridLayout; //控制面板布局

    setWindowTitle("QT绘图框架测试（QPainter）类");

    labelshap = new QLabel("绘制形状");

    comboboxShape = new QComboBox;

    comboboxShape->addItem("Line",PainterArea::Line);
    comboboxShape->addItem("Rectangle",PainterArea::Rectangle);

    glayout->addWidget(labelshap,0,0);
    glayout->addWidget(comboboxShape,0,1);

    QHBoxLayout *mainLayout= new QHBoxLayout(this); //整体布局
    mainLayout->addWidget(labelshapeArea); //向布局 添加控件
    mainLayout->addLayout(glayout); //向布局添加布局

    connect(comboboxShape,SIGNAL(activated(int)),this,SLOT(dispShapeFunc(int)));
}

Widget::~Widget()
{

}

void Widget::dispShapeFunc(int v)
{
    PainterArea::shape sp=PainterArea::shape(comboboxShape->itemData(v,Qt::UserRole).toInt());
    qDebug() << sp;
    labelshapeArea->setshape(sp);
}