QT中使用rubberband橡皮筋等方法进行选中多个物体

逃离我推掉我的手 2022-03-24 14:58 589阅读 0赞

### 文章目录 ###

*  功能介绍
 *  代码介绍
 *   *  myitem.h/cpp 图形项
     *  myview.h/cpp场景
     *  主函数
 *  结果展示
 *  代码下载
 *  参考

# 功能介绍 #

*  点击左键、按 Shift 键可以单选，按下 Ctrl 可进行多选。
 *  选中时候点击右键，可以选择隐藏物体，归位
 *  移动：点击左键，选择 item，然后移动鼠标

# 代码介绍 #

## myitem.h/cpp 图形项 ##

**myitem.h**

#ifndef MYITEM_H
    #define MYITEM_H
    
    #include <QGraphicsItem>
    
    class MyItem : public QGraphicsItem
    {
    public:
        MyItem();
        ~MyItem();
        QRectF boundingRect() const;
        void paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget);
        void setColor(const QColor &color){brushColor = color;};
    
    private:
        QColor brushColor;
    
    protected:
        void keyPressEvent(QKeyEvent *event);
        void mousePressEvent(QGraphicsSceneMouseEvent *event);
        void hoverEnterEvent(QGraphicsSceneMouseEvent *event);
        void contextMenuEvent(QGraphicsSceneContextMenuEvent *event);
    
    };
    
    #endif // MYITEM_H

**myitem.cpp**

#include "myitem.h"
    #include<QPainter>
    #include<QDebug>
    #include<QCursor>
    #include<QKeyEvent>
    #include<QGraphicsSceneHoverEvent>
    #include<QGraphicsSceneContextMenuEvent>
    #include<QMenu>
    
    MyItem::MyItem()
    {
        brushColor = Qt::red;
        //设置图形项可以移动
        setFlag(QGraphicsItem::ItemIsMovable);
        //设置图形项可以选择
        setFlag(QGraphicsItem::ItemIsSelectable);
        //设置接受鼠标悬停事件
        setAcceptHoverEvents(true);
    }
    
    MyItem::~MyItem()
    {
    
    }
    
    
    //设置包围盒，返回图形项矩形区域
    //详细信息参考：http://doc.qt.io/archives/qt-4.8/qgraphicsitem.html
    QRectF MyItem::boundingRect() const
    {
        //画笔宽度
        qreal adjust = 0.5;
        //因为paint函数中的矩形是以(-10,-10)为原点画出的长宽均为20的矩形
        return QRectF(-10 - adjust, -10 - adjust, 20 + adjust, 20 + adjust);
    }
    
    
    //执行实际的绘图操作
    void MyItem::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
    {
        //判断是否被选中
        if (isSelected()){
            //设置轮廓为白色
            painter->setPen(QPen(QColor(255, 255, 255, 200)));
        }else{
            painter->setPen(QPen(QColor(100, 100, 100, 100)));
        }
        //设置填充颜色
        painter->setBrush(brushColor);
        //绘制矩形
        painter->drawRect(-10, -10, 20, 20);
    }
    
    
    //键盘按下处理函数，判断是否向下按下方向键，是的话，则向下移动图形项
    void MyItem::keyPressEvent(QKeyEvent *event)
    {
        if (event->key() == Qt::Key_Down)
        {
            moveBy(0, 10);
        }
        else if (event->key() == Qt::Key_Up)
        {
            moveBy(0, -10);
        }
        else if (event->key() == Qt::Key_Right)
        {
            moveBy(10, 0);
        }
        else if (event->key() == Qt::Key_Left)
        {
            moveBy(-10, 0);
        }
    }
    
    
    //鼠标按下事件处理函数，设置被点击的图形项是否被选中，并改变外观
    //系统默认Ctrl+鼠标左键可实现多选
    void MyItem::mousePressEvent(QGraphicsSceneMouseEvent *event)
    {
        //设置鼠标形状
        setCursor(Qt::ClosedHandCursor);
        if (event->button() == Qt::LeftButton)
        {
            //设置shift+鼠标左键单选
            if (event->modifiers() == Qt::ShiftModifier)
            {
                qDebug() << "item left clicked with shift key";
                setSelected(true);
            }
            else
            {
                qDebug() << "item left clicked";
                QGraphicsItem::mousePressEvent(event);
            }
        }
    //	else if (event->button() == Qt::RightButton)
    //	{
    //		qDebug() << "item right clicked";
    //	}
    }
    
    //悬停事件处理函数，设置光标外观和提示
    void MyItem::hoverEnterEvent(QGraphicsSceneMouseEvent *event)
    {
        setCursor(Qt::OpenHandCursor);
    }
    
    //右键菜单事件处理函数，为图形项添加一个右键菜单
    void MyItem::contextMenuEvent(QGraphicsSceneContextMenuEvent *event)
    {
        QMenu menu;
        QAction *moveAction = menu.addAction("move back");
        QAction *hideAction = menu.addAction("hide");
        QAction *showAction = menu.addAction("show");
        QAction *selectedAction = menu.exec(event->screenPos());
        //让图形项归位到场景原点
        if (selectedAction == moveAction)
        {
            setPos(0, 0);
        }
        else if (selectedAction == hideAction)
        {
             setVisible(false);
        }
        else if (selectedAction == showAction)
        {
            setVisible(true);
        }
    }

## myview.h/cpp场景 ##

**myview.h**

#ifndef MYVIEW_H
    #define MYVIEW_H
    #include <QGraphicsView>
    
    class MyView : public QGraphicsView
    {
        Q_OBJECT
    public:
        explicit MyView(QWidget *parent = 0);
    //    MyView();
        ~MyView();
    
    protected:
        void mousePressEvent(QMouseEvent *event);
        void mouseReleaseEvent(QMouseEvent *event);
    
    };
    
    #endif // MYVIEW_H

**myview.cpp**

#include "myview.h"
    #include <QKeyEvent>
    #include <QMouseEvent>
    #include <QGraphicsView>
    
    MyView::MyView(QWidget *parent) :
        QGraphicsView(parent)
    {
        //设置橡皮筋选择选项
        setDragMode(QGraphicsView::RubberBandDrag);
    }
    
    MyView::~MyView()
    {
    
    }
    
    void MyView::mousePressEvent(QMouseEvent *event)
    {
        QGraphicsView::mousePressEvent(event);
    }
    
    void MyView::mouseReleaseEvent(QMouseEvent *event)
    {
        QGraphicsView::mouseReleaseEvent(event);
    }

## 主函数 ##

#include "myitem.h"
    #include "myview.h"
    #include <QApplication>
    #include <QTime>
    #include <QGraphicsScene>
    
    int main(int argc, char *argv[])
    {
        QApplication a(argc, argv);
        //设置随机种子
        qsrand(QTime(0, 0, 0).secsTo(QTime::currentTime()));
    
        //设置场景
        QGraphicsScene scene;
        scene.setSceneRect(-200, -150, 400, 300);
    
        //随机生成5个颜色不同的矩形
        for (int i = 0; i < 5; i++)
        {
            MyItem *item = new MyItem;
            item->setColor(QColor(qrand() % 256, qrand() % 256, qrand() % 256));
            item->setPos(i * 50 - 90, -50);
            //将图形项添加到场景中
            scene.addItem(item);
        }
    
        MyView view;
        //为视图添加场景
        view.setScene(&scene);
        //设置场景背景
        view.setBackgroundBrush(Qt::gray);
        //显示
        view.show();
    
        return a.exec();
    }

# 结果展示 #

![在这里插入图片描述][20190122112611529.gif]

# 代码下载 #

[https://download.csdn.net/download/sty945/10931750][https_download.csdn.net_download_sty945_10931750]

# 参考 #

[https://blog.csdn.net/liang19890820/article/details/53504323][https_blog.csdn.net_liang19890820_article_details_53504323]

[20190122112611529.gif]: /images/20220323/24b0b32451fc499ba3cc6b364d5e9d67.png
[https_download.csdn.net_download_sty945_10931750]: https://download.csdn.net/download/sty945/10931750
[https_blog.csdn.net_liang19890820_article_details_53504323]: https://blog.csdn.net/liang19890820/article/details/53504323