QT+=svg

QT+=svgwidgets

#include <QSvgWidget>
#include<QtSvg>
#include<QSvgRenderer>
public:
    void wheelEvent(QWheelEvent *);//響應(yīng)鼠標(biāo)的滾動(dòng)事件，使SVG圖片可以通過(guò)鼠標(biāo)滾動(dòng)進(jìn)行縮放
private:
    QSvgRenderer *render;//用于圖片顯示尺寸的確定

SvgWidget::SvgWidget()
{
    render=renderer();
}

void SvgWidget::wheelEvent(QWheelEvent *e)
{
    const double diff=0.1;//diff的值表示每次滾輪滾動(dòng)一定的值,圖片大小改變的比例
    //用于獲取圖片顯示區(qū)的尺寸
    QSize size=render->defaultSize();
    int width=size.width();
    int height=size.height();
    //利用QWheelEvent的相關(guān)函數(shù)獲得滾輪滾動(dòng)的距離值,通過(guò)此值判斷滾輪滾動(dòng)的方向
    //若此值大于0,則表示滾輪向前(遠(yuǎn)離用戶方向)滾動(dòng);
    //若此值小于0,則表示滾輪向后(靠近用戶方向)滾動(dòng);
    //Qt6使用e->angleDelta().y()
    //Qt5請(qǐng)使用e->delta()
    if(e->angleDelta().y()>0){
        //對(duì)圖片的長(zhǎng)、寬值進(jìn)行放大
        width=int(this->width()+this->width()*diff);
        height=int(this->height()+this->height()*diff);
    }else{
        //對(duì)圖片的長(zhǎng)、寬值進(jìn)行縮小
        width=int(this->width()-this->width()*diff);
        height=int(this->height()-this->height()*diff);
    }
    resize(width,height);//重新調(diào)整大小
}

#include"svgwidget.h"
public:
    void setFile(QString);
    void mousePressEvent(QMouseEvent *);
    void mouseMoveEvent(QMouseEvent *);
private:
    SvgWidget *svgWidget;
    QPoint mousePressPos;
    QPoint scrollBarValuesMousePress;

    svgWidget=new SvgWidget;
    setWidget(svgWidget);

//設(shè)置新的文件
void SvgWindow::setFile(QString filename){
    svgWidget->load(filename);//將新的SVG文件加載到svgWidget中進(jìn)行顯示
    QSvgRenderer *render=svgWidget->renderer();
    svgWidget->resize(render->defaultSize());//按照SVG文件的默認(rèn)尺寸進(jìn)行顯示
}

//鼠標(biāo)按下響應(yīng)函數(shù)
void SvgWindow::mousePressEvent(QMouseEvent *e)
{
    mousePressPos=e->pos();
    scrollBarValuesMousePress.rx()=horizontalScrollBar()->value();
    scrollBarValuesMousePress.ry()=verticalScrollBar()->value();
    e->accept();
}

//鼠標(biāo)按下且拖拽響應(yīng)函數(shù)
void SvgWindow::mouseMoveEvent(QMouseEvent *e)
{
    horizontalScrollBar()->setValue(scrollBarValuesMousePress.x()-
                                    e->pos().x()+mousePressPos.x());//對(duì)水平滾動(dòng)條的新位置進(jìn)行設(shè)置
    verticalScrollBar()->setValue(scrollBarValuesMousePress.y()-
                                  e->pos().y()+mousePressPos.y());//對(duì)垂直滾動(dòng)條的新位置進(jìn)行設(shè)置
    horizontalScrollBar()->update();
    verticalScrollBar()->update();
    e->accept();
}

#include"svgwindow.h"

public slots:
    void slotOpenFile();//打開文件槽函數(shù)

private:
    SvgWindow *svgwindow; //用于調(diào)用相關(guān)函數(shù)傳遞選擇的文件名

    setWindowTitle("SVG Viewer");//設(shè)置窗口標(biāo)題
    QMenu *fileMenu=menuBar()->addMenu("文件");//菜單欄添加"文件"
    QAction *openAct=new QAction("打開",this);//"文件"中添加"打開"子菜單
    connect(openAct,SIGNAL(triggered()),this,SLOT(slotOpenFile()));//點(diǎn)擊打開觸發(fā)slotOpenFile()槽函數(shù)
    fileMenu->addAction(openAct);
    svgwindow=new SvgWindow;
    setCentralWidget(svgwindow);
    resize(800,600);//初始大小

//打開菜單的槽函數(shù)
void MainWindow::slotOpenFile()
{
    QString name=QFileDialog::getOpenFileName(this,"打開","/","svg files(*.svg)");
    svgwindow->setFile(name);
}