Qt学习（六） 软件启动界面 ，注册表使用 ，QT绘图， 视图和窗口绘图，Graphics View绘图框架：简易CAD

一 软件启动界面 注册表使用

• 知识点1：这样创建的界面是不可以拖动的，需要手动创建函数来进行拖动，以下的3个函数是从父类继承过来的函数

    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);

步骤1：新建Qt设计师类，进行界面设计

• 添加背景图片，label标签，pixmap可以直接在标签所在位置插入图片
  
  
• 对于确认和取消按钮里面的图片，在如下所示地方插入即可
  

步骤2：main.cpp文件中，添加对话框

#include "mainwindow.h"
#include <QApplication>
#include "dialoglogin.h"
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    DialogLogin *login = new DialogLogin();
    if(login->exec() != QDialog::Accepted)
    {
        return 0;
    }

    MainWindow w;
    w.show();
    return a.exec();
}

步骤3：代码

• dialoglogin.h

#ifndef DIALOGLOGIN_H
#define DIALOGLOGIN_H
#include <QDialog>
namespace Ui {
class DialogLogin;
}
class DialogLogin : public QDialog
{
    Q_OBJECT
public:
    explicit DialogLogin(QWidget *parent = nullptr);
    ~DialogLogin();
private slots:
    void on_pushButtonCancle_clicked();
    void on_pushButtonLog_clicked();
private:
    Ui::DialogLogin *ui;

    void loadSetting(); //读取本地的配置
    void saveSetting();
    QString m_user;
    QString m_pwd;
    int m_count = 0;
    QString Encrypt(const QString &str); //对密码加密

    bool m_moving= false;
    QPoint m_lastPosition;
    virtual void mousePressEvent(QMouseEvent *event);
    virtual void mouseReleaseEvent(QMouseEvent *event);
    virtual void mouseMoveEvent(QMouseEvent *event);
};

#endif // DIALOGLOGIN_H

• dialoglogin.cpp

#include "dialoglogin.h"
#include "ui_dialoglogin.h"
#include <QSettings>
#include <QCryptographicHash>
#include <QMessageBox>
#include <QMouseEvent>

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

    //设置密码
    ui->lineEditNameCode->setEchoMode(QLineEdit::Password);
    this->setAttribute(Qt::WA_DeleteOnClose);

    //去掉登录窗口的左上角的标题
    this->setWindowFlags(Qt::FramelessWindowHint);  //任务栏中会显示标题
    //this->setWindowFlag(Qt::SplashScreen); //任务栏中也不会显示标题

    //读取本地电脑存储的用户名和密码，演示注册表的使用
    loadSetting();
}

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

void DialogLogin::on_pushButtonCancle_clicked()
{
    this->reject();
}

void DialogLogin::on_pushButtonLog_clicked()
{
    QString useName = ui->lineEditName->text().trimmed();  //trimmed去掉首位空格
    QString pwd = ui->lineEditNameCode->text().trimmed();
    if(useName == m_user && Encrypt(pwd) == m_pwd){
        //保存注册表
        saveSetting();
        this->accept();
    }else{
        m_count ++;
        if(m_count > 3)
        {
            QMessageBox::critical(this,"错误","用户名和密码错误次数太多");
            this->reject();
        }
        else{
            QMessageBox::warning(this,"错误","用户名和密码错误");
        }
    }

}

void DialogLogin::loadSetting()
{
    QSettings setting("WD","IMAGE PROCESSING");  //公司名字 当前软件名字
    m_user = setting.value("user_name", "rook").toString();   //读默认值
    m_pwd = setting.value("pwd", Encrypt("123456")).toString();

    bool saved = setting.value("saved",false).toBool(); //默认保存

    if(saved){
        ui->lineEditName->setText(m_user);
        ui->checkBox->setChecked(saved);
    }
}

void DialogLogin::saveSetting()
{
     QSettings setting("WD","IMAGE PROCESSING");
     setting.setValue("user_name", m_user);
     setting.setValue("pwd", m_pwd);
     setting.setValue("saved", ui->checkBox->isChecked());
}

QString DialogLogin::Encrypt(const QString &str)
{
    //MD5加密
    QByteArray array;
    array.append(str);
    QCryptographicHash hash(QCryptographicHash::Md5); //设置加密算法
    hash.addData(array);

    QByteArray result = hash.result();
    QString md5 = result.toHex();
    return md5;
}

void DialogLogin::mousePressEvent(QMouseEvent *event)
{
    if(event->button() ==Qt::LeftButton){
            m_moving = true;
            m_lastPosition = event->globalPos() - this->pos();
    }

    return QDialog::mousePressEvent(event);
}

void DialogLogin::mouseReleaseEvent(QMouseEvent *event)
{
    m_moving = false;
}

void DialogLogin::mouseMoveEvent(QMouseEvent *event)
{
    if(m_moving){
        move(event->globalPos() - m_lastPosition);
        m_lastPosition = event->globalPos()- this->pos();
    }
    return QDialog::mouseMoveEvent(event);
}

• mainwindow.cpp和mainwindow.h文件没有任何改变和代码添加

二 QT绘图

2.1 矩形

• 知识点：需要重写父类的virtual void paintEvent(QPaintEvent *event);

• widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Ui::Widget *ui;
    virtual void paintEvent(QPaintEvent *event);
};
#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);
}

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

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);

    QPen pen;
    pen.setWidth(4);  //线宽
    pen.setColor(Qt::red);
    painter.setPen(pen);

    //使用刷子进行填充
    QBrush brush;
    brush.setColor(Qt::green);
    brush.setStyle(Qt::SolidPattern);
    painter.setBrush(brush);

    QRect rect(50,50,200,200);  //左上角坐标（x，y,宽度，高度)
    painter.drawRect(rect);

}

2.1.1

• 圆角矩形：将2.1 函数void Widget::paintEvent(QPaintEvent *event)中 painter.drawRect(rect);代码修改为 painter.drawRoundedRect(rect,20,20);
• 椭圆：painter.drawEllipse(rect);
• 圆弧： //绘制圆弧 绘制0~90度 painter.drawArc(rect,0,90*16);，Qt最小度单位不是1度，是1/16度
• 弦长：painter.drawChord(rect, 0,*16,90*16)
• 多边形：

QPainter painter(this);
QPen
pen;
pen.setWidth(4); //线宽
pen.setColor(Qt::red); //划线颜色
painter.setPen(pen);
//注意，点的顺序，就是绘制的顺序
QPoint points[5] = {
{50, 100},
{100, 50},
{500, 160},
{200, 200},
{110, 400}};
painter.drawPolygon(
points,
5); //表示有几个点

• 图片

void Widget::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QRect rect(10, 10, 400, 300);
//QImage image(":image/bg.png");
QPixmap pixmap(":image/bg.png");
//会自动在 rect 区域进行缩放
//painter.drawImage(rect, image);
painter.drawPixmap(rect, pixmap);
}

• 直线

void Widget::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QPen
pen;
pen.setWidth(4); //线宽
pen.setColor(Qt::red); //划线颜色
painter.setPen(pen);
QLine line(50, 50, 400, 400);
painter.drawLine(line);
}

• 多条直线

void Widget::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QPen
pen;
pen.setWidth(4); //线宽
pen.setColor(Qt::red); //划线颜色
painter.setPen(pen);
QRect rect(50, 50, 400, 300);
QVector<QLine>lines;
lines.append(QLine(rect.topLeft(), rect.bottomRight()));
lines.append(QLine(rect.bottomLeft(), rect.topRight()));
lines.append(QLine(rect.topLeft(), rect.bottomLeft()));
painter.drawLines(lines);
}

• 绘制多条连接的直线

void Widget::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QPen
pen;
pen.setWidth(4); //线宽
pen.setColor(Qt::red); //划线颜色
painter.setPen(pen);
//注意，点的顺序，就是绘制的顺序
QPoint points[5] = {
{50, 100},
{100, 50},
{500, 160},
{200, 200},
{110, 400}};
painter.drawPolyline(points, 5);
}

• 绘制线路径

void Widget::paintEvent(QPaintEvent *event)
{
QPainter painter(this);
QPen
pen;
pen.setWidth(4); //线宽
pen.setColor(Qt::red); //划线颜色
painter.setPen(pen);
QRect rect(50, 50, 400, 300);
//绘制由 QPaintPath 对象定义的路线
QPainterPath path;
path.addEllipse(rect); //在 rect 内的内接椭圆
path.addRect(rect);
painter.drawPath(path);
}

• 绘制扇形
  
• 画点
  
• 绘制文本
  
• 擦除指定区域
• 
• 填充指定位置
  

三 坐标变换

3.1 平移

• 知识点：依然是需要继承父类的void Widget::paintEvent(QPaintEvent *event)函数，在改函数内进行相应的实现

3.2 旋转

3.3 扭转

3.4 放大缩小

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    QImage img(":/images/bg.png");

    QRect rect(0,0,200,150);
    painter.drawImage(rect,img);

    QRect rect2(200,200,200,150);
    painter.scale(2.0,1.0);
    painter.drawImage(rect2,img);

}

3.5 案例展示

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing); //使得图行没有锯齿

    QPen  pen;
    pen.setWidth(4);
    pen.setColor(Qt::red);
    painter.setPen(pen);

    QFont font;
    font.setPointSize(20);
    painter.setFont(font);

    qreal r = 200;  //qreal其实就是double
    qreal unit = 72*3.141596/180;

    QPoint points[5] = {
        QPoint(r,0),
        QPoint(r*cos(unit),r*sin(unit)),
        QPoint(r*cos(2*unit),r*sin(2*unit)),
        QPoint(r*cos(3*unit),r*sin(3*unit)),
        QPoint(r*cos(4*unit),r*sin(4*unit))
    };

    QPainterPath path;
    path.moveTo(points[0]);  //把画笔移动到该位置
    path.lineTo(points[2]);
    path.lineTo(points[4]);
    path.lineTo(points[1]);
    path.lineTo(points[3]);
    path.closeSubpath();

    path.addText(points[0],font,"0");
    path.addText(points[1],font,"1");
    path.addText(points[2],font,"2");
    path.addText(points[3],font,"3");
    path.addText(points[4],font,"4");

    //保存此时坐标
    painter.save();
    painter.translate(250,210);
    painter.rotate(-18);

    painter.drawPath(path);
    painter.restore();

}

四 视图和窗口绘图

• 功能，能使得建立的图片，随着窗口的大小变化而变化
• 知识点：需要重写void paintEvent( QPaintEvent *event);
• 知识点：也就是说，painter.setWindow是重定义视口的原点的逻辑大小

案例1：

void Widget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);

    //设计一个视口，也即是绘图窗口
    QPainter painter(this);
    painter.drawRect(QRect(200,0,200,200));

    painter.setViewport(
                200,0,    //视口区域的左上角坐标，实际大小
                200,200); //视口区域的左上角宽度和高度，实际大小

	//设置视口后，一定要设置对应的窗口坐标
	//否则会使用默认的窗口坐标，导致绘制效果不是预期的
	//如下代码表示在当前的视口区域内，设置一个窗口坐标，
	//在这个窗口坐标下，视口的左上角坐标是（-50， -50），
	//视口的宽度是 100 个逻辑大小，视口的高度是 100 个逻辑大小
    painter.setWindow(
                -50,-50,  //在这个窗口坐标系下，视口左上角的坐标
                100, //在这个窗口坐标系下，视图区域的宽度大小，逻辑大小，不是实际大小
                100);//在这个窗口坐标系下，视图区域的高度大小，逻辑大小，不是实际大小

    QPen pen;
    pen.setColor(Qt::red);
    painter.setPen(pen);

    painter.drawRect(QRect(0,0,50,50));
}

案例2：

void Widget::paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);

    //设计一个视口，也即是绘图窗口
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);

    int w= qMin(this->width(), this->height());
    QRect rect((this->width() - w)/2,(this->height() - w)/2,w,w);
    painter.drawRect(rect);


    //设置视口区域
    painter.setViewport(rect);
    //设置视口的窗口坐标系
    painter.setWindow(-100,-100,200,200);

    QPen pen;
    pen.setColor(Qt::red);
    pen.setWidth(1);
    pen.setStyle(Qt::SolidLine);
    painter.setPen(pen);

    int count = 10;
    for(int i =0; i< count ;i ++){
        painter.drawEllipse(QPoint(50,0),50,50);
        painter.rotate(360/count);
    }
}

五 Graphics View绘图框架

5.1 案例1 视图，场景，图形项之间的关系

• 知识点1： scene->addItem(item3);默认父节点是场景，如果要设置其他的图形项是当前图i图形项目的父节点，需要使用函数`item->setParentItem(item2)
• 知识点2：设置item可拖动

    item2->setFlags(QGraphicsItem::ItemIsSelectable |
                    QGraphicsItem::ItemIsMovable |
                    QGraphicsItem::ItemIsFocusable);

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

    //创建场景，当前的原点创建在了场景的中心
    scene =  new QGraphicsScene(-200,-100,   //场景区域的左上角在场景坐标下的坐标，也就是原点被设置成矩形框的正中心
                                400,200);  //场景的宽度，场景的高度
    ui->graphicsView->setScene(scene);


    //图形项 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item = new QGraphicsRectItem(
                                    -200,-100,  //矩形图形项的左上角在图像项内部的坐标系下的坐标
                                    400,200);

    //设置图形项的原点，在场景坐标系下的位置
    item->setPos(0,0);

    //设置图形项的画笔
    QPen pen;
    pen.setColor(Qt::blue);
    pen.setWidth(2);
    item->setPen(pen);

    scene->addItem(item);


    //图形项2 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item2 = new QGraphicsRectItem(
                                       0,0,  //矩形图形项的左上角在图像项内部的坐标系下的坐标，也就是原点被设置成左上角
                                       200,100);
    //设置图形项的原点，在场景坐标系下的位置
    item2->setPos(-200,-100);
    item2->setBrush(QBrush(Qt::red));
    scene->addItem(item2);


    //图形项2 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item3 = new QGraphicsRectItem(
                                        -100,-50,  //矩形图形项的左上角在图像项内部的坐标系下的坐标，也就是原点被设置图形项的正中心
                                        200,100);

    //设置图形项的原点，在场景坐标系下的位置,
    item3->setPos(0,0);
    item3->setBrush(QBrush(Qt::yellow));
    scene->addItem(item3);默认父节点是场景
}

5.1 案例2： 拖动鼠标或者图形项，显示鼠标当前所在位置的，对应的视图，场景以及图形项中的坐标

• 也是图形项发出信号

• mainwindow

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsScene>
#include "mygraphicview.h"

QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    QGraphicsScene *scene;

private slots:
    void on_graphicsView_mousePress(QPoint point);
    void on_graphicsView_mouseMove(QPoint point);
};
#endif // MAINWINDOW_H

#######################################################################################
#######################################################################################
#######################################################################################
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QGraphicsRectItem>

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

    //创建场景，当前的原点创建在了场景的中心
    scene =  new QGraphicsScene(-200,-100,   //场景区域的左上角在场景坐标下的坐标，也就是原点被设置成矩形框的正中心
                                400,200);  //场景的宽度，场景的高度
    ui->graphicsView->setScene(scene);


    //图形项 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item = new QGraphicsRectItem(
                                    -200,-100,  //矩形图形项的左上角在图像项内部的坐标系下的坐标
                                    400,200);

    //设置图形项的原点，在场景坐标系下的位置
    item->setPos(0,0);

    //设置图形项的画笔
    QPen pen;
    pen.setColor(Qt::blue);
    pen.setWidth(2);
    item->setPen(pen);

    scene->addItem(item);


    //图形项2 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item2 = new QGraphicsRectItem(
                                       0,0,  //矩形图形项的左上角在图像项内部的坐标系下的坐标，也就是原点被设置成左上角
                                       200,100);
    //设置图形项的原点，在场景坐标系下的位置
    item2->setPos(-200,-100);
    item2->setBrush(QBrush(Qt::red));
    scene->addItem(item2);
    item2->setFlags(QGraphicsItem::ItemIsSelectable |
                    QGraphicsItem::ItemIsMovable |
                    QGraphicsItem::ItemIsFocusable);

    //图形项2 当前创建了和场景一样大小的图形项
    QGraphicsRectItem *item3 = new QGraphicsRectItem(
                                        -100,-50,  //矩形图形项的左上角在图像项内部的坐标系下的坐标，也就是原点被设置图形项的正中心
                                        200,100);

    //设置图形项的原点，在场景坐标系下的位置,
    item3->setPos(0,0);
    item3->setBrush(QBrush(Qt::yellow));
    scene->addItem(item3);


}

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

void MainWindow::on_graphicsView_mousePress(QPoint point)
{
    //把视图坐标转换成场景坐标
    QPointF pointSence =ui->graphicsView->mapToScene(point);

    //判断当前按下了哪个图形项
    QGraphicsItem *item = scene->itemAt(pointSence,ui->graphicsView->transform());

    if(item)
    {
        //把场景坐标，进一步转换成对应的图形项的坐标
        QPointF pointItem = item->mapFromScene(pointSence);
        ui->labelGraph->setText(QString::asprintf("item坐标：%.0f, %.0f",
                                 pointItem.x(),pointItem.y() ));
    }
}

void MainWindow::on_graphicsView_mouseMove(QPoint point)
{
    ui->labelView->setText(QString::asprintf("视图坐标：%d, %d",
                                             point.x(),point.y() ));
    QPointF pointSence =ui->graphicsView->mapToScene(point);
    ui->labelSence->setText(QString::asprintf("场景坐标：%.0f, %.0f",
                                             pointSence.x(),pointSence.y() ));
}

• MyGraphicView

#ifndef MYGRAPHICVIEW_H
#define MYGRAPHICVIEW_H

#include <QObject>
#include <QGraphicsView>

class MyGraphicView : public QGraphicsView
{
    Q_OBJECT
public:
    explicit MyGraphicView(QObject *parent = nullptr);

signals:
    //这里是自己定义的，不是查的
    void mousePress(QPoint point);
    void mouseMove(QPoint point);
private:
    //重载父类QGraphicsView鼠标事件
    void mousePressEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
};

#endif // MYGRAPHICVIEW_H

#######################################################################################
#######################################################################################
#######################################################################################
#include "mygraphicview.h"
#include <QMouseEvent>
MyGraphicView::MyGraphicView(QObject *parent)
{
    setMouseTracking(true); //直接拖动鼠标，也能显示坐标的改变
}

void MyGraphicView::mousePressEvent(QMouseEvent *event)
{
    if(event->button() == Qt::LeftButton){
        QPoint point = event->pos();
        emit mousePress(point);
    }
    QGraphicsView::mousePressEvent(event); //调用父类的mousePressEvent
}

void MyGraphicView::mouseMoveEvent(QMouseEvent *event)
{
    QPoint point = event->pos();
    emit mouseMove(point);

    QGraphicsView::mouseMoveEvent(event); //调用父类的mouseMoveEvent
}

5.1.1 创建项目的步骤

-Graphics View组件对应的类对象是QGraphicsView，是标准类对象，无法进行修改，需要自定义一个视图，去重载该类的鼠标事件

步骤1：自定义视图类

• add new->c++ class->QObject
  选项里面并没有我们要继承的QGraphicsView类，所以可以随便选一个要继承的类，在代码里进行修改即可
  

步骤2：修改自定义视图类，使其继承QGraphicsView，在QGraphicsView中寻找到鼠标相关时事件，在自定义视图类中重写。由于本身本没有信号，但是要实现鼠标移动或单击时发送信号，因此要MyGraphicView中定义信号，在mianwindow中定义槽函数

`MyGraphicView`

signals:
    //这里是自己定义的，不是查的
    void mousePress(QPoint point);
    void mouseMove(QPoint point);
private:
    //重载父类QGraphicsView鼠标事件
    void mousePressEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;

mainwindow


private slots:
    void on_graphicsView_mousePress(QPoint point);
    void on_graphicsView_mouseMove(QPoint point);

步骤3：选中graphics View组件，右键单击，选择提升为，

6 案例2 简易版CAD项目

• 知识点：如何添加侧面的toolbox
  

6.1 创建界面

1. 定义界面

2.自定义mygraphicsview.h``,Add new->c++->c++ class ->父类选择Qobject, 步骤同5中的创建步骤，新定义的继承QObject类的来要修改成继承QGraphicsView`

6.2 代码

• mainWindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QGraphicsScene>
#include <QLabel>
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();

private:
    Ui::MainWindow *ui;
    QGraphicsScene *sence;

    int itemZvalue = 0;  //图形堆叠的顺序，数字越大，叠放越上面

    int itemID =0;
    static const int ITEM_ID = 1; //图形项的编号
    static const int ITEM_DISCRIPTION = 2;  //图形项的描述信息

    //手动代码添加标签
     QLabel *labelViewCoord;  //视图坐标
     QLabel *labelFigureCoord;   //图形项坐标
     QLabel *labelSenceCoord;   //场景坐标
     QLabel *itemName;
private slots:
    void on_graphicsView_keyPress(QKeyEvent *event);
    void on_graphicsView_mouseDouble(QPoint point);
    void on_graphicsView_mousePress(QPoint point);
    void on_graphicsView_mouseMove(QPoint point);

    void on_actionRectangle_triggered();
    void on_actionElipse_triggered();
    void on_actionCilcle_triggered();
    void on_actionTriangle_triggered();
    void on_actionLine_triggered();
    void on_actionTixing_triggered();
    void on_actionText_triggered();
    void on_actionZoom_triggered();
    void on_actionSmall_triggered();
    void on_actionRestore_triggered();
    void on_actionLeft_triggered();
    void on_actionRight_triggered();
    void on_actionTop_triggered();
    void on_actionBottom_triggered();
    void on_actionCombine_triggered();
    void on_actionDepart_triggered();
    void on_actionDel_triggered();
    void on_actionExit_triggered();
};
#endif // MAINWINDOW_H

• mygraphicsview.h

#ifndef MYGRAPHICSVIEW_H
#define MYGRAPHICSVIEW_H

#include <QObject>
#include <QGraphicsView>

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

signals:
    void keyPress(QKeyEvent *event);
    void mouseDouble(QPoint point);
    void mousePress(QPoint point);
    void mouseMove(QPoint point);
protected:
    //override重载关键字
    void keyPressEvent(QKeyEvent *event) override;  //按键按下
    void mouseDoubleClickEvent(QMouseEvent *event) override;
    void mousePressEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
};

#endif // MYGRAPHICSVIEW_H

• mainWindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QGraphicsRectItem>
#include <QTime>
#include <QPoint>
#include <QInputDialog>
#include <QDebug>
#include <QColorDialog>
#include <QColor>
#include <QFontDialog>
#include <QKeyEvent>
//设置填充色
template <class T>
void setItemBrushColor(T *item){
   QColor color = item->brush().color();
   color = QColorDialog::getColor(color, NULL, "选择填充颜色");
   if(color.isValid()){
       item->setBrush(color);
   }
}

//设置画笔色
template <class T>
void setItemPenColor(T *item){
   QPen pen = item->pen();
   QColor color = pen.color();
   color = QColorDialog::getColor(color, NULL, "选择填充颜色");
   if(color.isValid()){
       pen.setColor(color);
       item->setPen(pen);
   }
}

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

    ui->graphicsView->setCursor(Qt::CrossCursor); //设置鼠标样式是十字

    //设置鼠标跟踪
    ui->graphicsView->setMouseTracking(true);

    //设置视图的拖动模式
    ui->graphicsView->setDragMode(QGraphicsView::RubberBandDrag);

    //创建场景
    sence = new QGraphicsScene(-300,-100,600,200);
    ui->graphicsView->setScene(sence);

    //设置随机种子
    qsrand(QTime::currentTime().second());


    labelViewCoord = new QLabel("视图坐标:");
    labelViewCoord->setMinimumWidth(150);
    ui->statusbar->addWidget(labelViewCoord);


    labelSenceCoord = new QLabel("场景坐标:");
    labelSenceCoord->setMinimumWidth(150);
    ui->statusbar->addWidget(labelSenceCoord);

    labelFigureCoord = new QLabel("图形项坐标:");
    labelFigureCoord->setMinimumWidth(150);
    ui->statusbar->addWidget(labelFigureCoord);


    itemName = new QLabel("图形项信息:");
    itemName->setMinimumWidth(150);
    ui->statusbar->addWidget(itemName);



}

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

//按键控制旋转平移操作
void MainWindow::on_graphicsView_keyPress(QKeyEvent *event)
{
    //只管选一个的情况
    if(sence->selectedItems().count() != 1){
        return;
    }

    auto item = sence->selectedItems().at(0);
    if(event->key() == Qt::Key_Delete){
        sence->removeItem(item);
    }else if(event->key() == Qt::Key_Space){
        item->setRotation(item->rotation() + 10);
    }else if(event->key() == Qt::Key_PageUp){
        item->setScale(item->scale() +0.1);
    }else if(event->key() == Qt::Key_PageDown){
        item->setScale(item->scale() -0.1);
    }else if(event->key() == Qt::Key_Left){
        item->setX(item->x() -1);
    }else if(event->key() == Qt::Key_Right){
        item->setX(item->x() +1);
    }else if(event->key() == Qt::Key_Up){
        item->setY(item->y() -1);
    }else if(event->key() == Qt::Key_Down){
            item->setY(item->y() +1);
    }

}

void MainWindow::on_graphicsView_mouseDouble(QPoint point)
{
    //双击图形项，自动弹出颜色编辑器
    //QGraphicsRectItem : public QAbstractGraphicsShapeItem
   // QGraphicsEllipseItem : public QAbstractGraphicsShapeItem
    //QGraphicsPolygonItem : public QAbstractGraphicsShapeItem 三角形
    //QGraphicsPolygonItem : public QAbstractGraphicsShapeItem 梯形

    qDebug() << "in in --------------";
    //由于不同图形继承的类不同
    QPointF pointSence = ui->graphicsView->mapToScene(point);  //获取场景坐标
    QGraphicsItem *item = sence->itemAt(pointSence, ui->graphicsView->transform()); //计算改场景坐标对应是哪个图形
    if(!item){
        return;
    }

    switch (item->type()) {
    case QGraphicsRectItem::Type:{
        //矩形
        auto item2 =qgraphicsitem_cast<QGraphicsRectItem*>(item);
        setItemBrushColor(item2);
        break;
    }
    case QGraphicsEllipseItem::Type:{
        //椭圆/园
        auto item2 =qgraphicsitem_cast<QGraphicsEllipseItem*>(item);
        setItemBrushColor(item2);
        break;
    }
    case QGraphicsPolygonItem::Type:{
        //多边形
        auto item2 =qgraphicsitem_cast<QGraphicsPolygonItem*>(item);
        setItemBrushColor(item2);
        break;
    }
    case QGraphicsLineItem::Type:{
        //直线
        auto item2 =qgraphicsitem_cast<QGraphicsLineItem*>(item);
        setItemPenColor(item2);
        break;
    }
    case QGraphicsTextItem::Type:{
        //多边形
        auto item2 =qgraphicsitem_cast<QGraphicsTextItem*>(item);
        QFont font = item2->font();
        bool ok = false;
        font = QFontDialog::getFont(&ok,font, this,"设置字体");
        if(ok)
        {
            item2->setFont(font);
        }
        break;
    }
    }
}

//图形项目坐标需要单击选中图形项 
void MainWindow::on_graphicsView_mousePress(QPoint point)
{
    QPointF pointScene = ui->graphicsView->mapToScene(point);  //视图坐标转场景坐标
    QGraphicsItem *item = sence->itemAt(pointScene,
                                        ui->graphicsView->transform());

    //图形项坐标
    if(item){
        QPointF pointItem = item->mapFromScene(pointScene);  //获取点的图形项坐标
        labelFigureCoord->setText(QString::asprintf("图形项坐标：%.0f %.0f",pointItem.x(),pointItem.y()));
        itemName->setText(item->data(ITEM_DISCRIPTION).toString());
    }

}

void MainWindow::on_graphicsView_mouseMove(QPoint point)
{
    labelViewCoord->setText(QString::asprintf("视图坐标：%d %d",point.x(),point.y()));
    QPointF pointScene = ui->graphicsView->mapToScene(point);
    labelSenceCoord->setText(QString::asprintf("场景坐标：%.0f %.0f",pointScene.x(),pointScene.y()));
}


void MainWindow::on_actionRectangle_triggered()
{
    QGraphicsRectItem *item = new QGraphicsRectItem(-100,-50,200,100);
    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setBrush(QBrush(Qt::lightGray));  //填充颜色
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"矩形");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionElipse_triggered()
{
    QGraphicsEllipseItem *item = new QGraphicsEllipseItem(-100,-50,200,100);
    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setBrush(QBrush(Qt::blue));  //填充颜色
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"椭圆");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionCilcle_triggered()
{
    QGraphicsEllipseItem *item = new QGraphicsEllipseItem(-100,-100,200,200);
    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setBrush(QBrush(Qt::yellow));  //填充颜色
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"圆");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionTriangle_triggered()
{
    QGraphicsPolygonItem *item = new QGraphicsPolygonItem;

    QPolygonF points;
    points.append(QPointF(0,-80));
    points.append(QPointF(-50,0));
    points.append(QPointF(0,50));
    item->setPolygon(points);

    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setBrush(QBrush(Qt::red));  //填充颜色
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"三角形");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionLine_triggered()
{
    QGraphicsLineItem *item = new QGraphicsLineItem(50, 50, 200, 200);

    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"直线");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionTixing_triggered()
{
    QGraphicsPolygonItem *item = new QGraphicsPolygonItem;

    QPolygonF points;
    points.append(QPointF(-50,-50));
    points.append(QPointF(-100,50));
    points.append(QPointF(100,50));
    points.append(QPointF(50,-50));
    item->setPolygon(points);

    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);
    item->setBrush(QBrush(Qt::black));  //填充颜色
    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"梯形");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionText_triggered()
{
    //弹出文本提示框，输入文本
    QString str = QInputDialog::getText(this,"输入文本","请输入文本");
    if(str.isEmpty()){
        return;
    }

    QGraphicsTextItem *item = new QGraphicsTextItem(str);
    item->setFlags(QGraphicsItem::ItemIsMovable |
                   QGraphicsItem::ItemIsFocusable |
                   QGraphicsItem:: ItemIsSelectable);

    QFont font;
    font.setFamily("微软雅黑");
    font.setPointSize(20);
    font.setBold(true);
    item->setFont(font);

    item->setZValue(itemZvalue++);

    //设置图形项位置，在视图的中心位置附近设计随机变量 0~100 -50
    item->setPos(qrand()%100-50,qrand()%100-50);

    //设置图形项的自定义数据
    item->setData(ITEM_ID,itemID++);
    item->setData(ITEM_DISCRIPTION,"文本");

    sence->addItem(item);
    sence->clearSelection();
    item->setSelected(true); //选中当前新生成的图形
}

void MainWindow::on_actionZoom_triggered()
{
    //如果当前选择了一个图元，那么对这个图元进行放大
    //如果选择了多个图，对多个放大
    int count = sence->selectedItems().count();
    if(count ==1)
    {
       QGraphicsItem *item= sence->selectedItems().at(0); //取出图形
       item->setScale(item->scale()+0.1);
    }else if(count >1)
    {
        for(int i =0 ; i < count; i++)
        {
            QGraphicsItem *item= sence->selectedItems().at(i); //取出图形
            item->setScale(item->scale()+0.1);
        }
    }
}

void MainWindow::on_actionSmall_triggered()
{
    int count = sence->selectedItems().count();
    if(count ==1)
    {
       QGraphicsItem *item= sence->selectedItems().at(0); //取出图形
       item->setScale(item->scale()-0.1);
    }else if(count >1)
    {
        for(int i =0 ; i < count; i++)
        {
            QGraphicsItem *item= sence->selectedItems().at(i); //取出图形
            item->setScale(item->scale()-0.1);
        }
    }
}

void MainWindow::on_actionRestore_triggered()
{
    int count = sence->selectedItems().count();
    for(int i =0 ; i < count; i++)
    {
        QGraphicsItem *item= sence->selectedItems().at(i); //取出图形
        item->setScale(1);
        item->setRotation(0);
    }
}

void MainWindow::on_actionLeft_triggered()
{
    int count = sence->selectedItems().count();
    if(count ==1)
    {
       QGraphicsItem *item= sence->selectedItems().at(0); //取出图形
       item->setRotation(item->rotation()-30);
    }else if(count >1)
    {
        for(int i =0 ; i < count; i++)
        {
            QGraphicsItem *item= sence->selectedItems().at(i); //取出图形
            item->setRotation(item->rotation()-30);
        }
    }
}

void MainWindow::on_actionRight_triggered()
{
    int count = sence->selectedItems().count();
    if(count ==1)
    {
       QGraphicsItem *item= sence->selectedItems().at(0); //取出图形
       item->setRotation(item->rotation()+30);
    }else if(count >1)
    {
        for(int i =0 ; i < count; i++)
        {
            QGraphicsItem *item= sence->selectedItems().at(i); //取出图形
            item->setRotation(item->rotation()+30);
        }
    }
}

void MainWindow::on_actionTop_triggered()
{
    int count = sence->selectedItems().count();
    if(count >0)
    {
        QGraphicsItem *item= sence->selectedItems().at(0);
        item->setZValue(item->zValue()+1);
    }
}

void MainWindow::on_actionBottom_triggered()
{
    int count = sence->selectedItems().count();
    if(count >0)
    {
        QGraphicsItem *item= sence->selectedItems().at(0);
        item->setZValue(item->zValue()-1);
    }
}

void MainWindow::on_actionCombine_triggered()
{
    int count = sence->selectedItems().count();
    qDebug() <<"count = " << count;
    if(count >=2)
    {
        QGraphicsItemGroup *group = new QGraphicsItemGroup;
        sence->addItem(group);
        for(int i =0 ; i < count; i++)
        {
            auto item = sence->selectedItems().at(0);  //获取每次循环的第一个item
            item->setSelected(false);
            item->clearFocus();
            group->addToGroup(item);
        }

        group->setFlags(QGraphicsItem::ItemIsMovable |
                        QGraphicsItem::ItemIsFocusable |
                        QGraphicsItem:: ItemIsSelectable);

        group->setZValue(itemZvalue++);
        sence->clearSelection();
        group->setSelected(true);
    }
}

void MainWindow::on_actionDepart_triggered()
{
    int count = sence->selectedItems().count();
    if(count ==1)
    {
        auto group = (QGraphicsItemGroup *)sence->selectedItems().at(0);
        sence->destroyItemGroup(group);
    }
}

void MainWindow::on_actionDel_triggered()
{
        int count = sence->selectedItems().count();
        if(count > 0){
            auto item = sence->selectedItems().at(0);
            sence->removeItem(item);
        }
}

void MainWindow::on_actionExit_triggered()
{
    close();
}

• mygraphicsview.cpp

#include "mygraphicsview.h"
#include <QMouseEvent>
#include <QDebug>
MyGraphicsView::MyGraphicsView(QWidget *parent):QGraphicsView(parent)
{

}

void MyGraphicsView::keyPressEvent(QKeyEvent *event)
{
    emit keyPress(event);
    QGraphicsView::keyPressEvent(event);
}

void MyGraphicsView::mouseDoubleClickEvent(QMouseEvent *event)
{
    //qDebug() << "mouseDoubleClickEvent ";

    if(event->button() == Qt::LeftButton){
        //获取视图坐标
        QPoint point = event->pos();
        emit mouseDouble(point);
    }
    QGraphicsView::mouseDoubleClickEvent(event);
}

void MyGraphicsView::mousePressEvent(QMouseEvent *event)
{

    if(event->button() == Qt::LeftButton){
        //获取视图坐标
        QPoint point = event->pos();
        emit mousePress(point);
    }
    QGraphicsView::mousePressEvent(event);
}

void MyGraphicsView::mouseMoveEvent(QMouseEvent *event)
{
    QPoint point = event->pos();
    emit mouseMove(point);
    QGraphicsView::mouseMoveEvent(event);
}