#include"scanline.h" #include"qpainter.h" #include<QDebug> #include "mainwindow.h" #include "ui_mainwindow.h" ScanLine::ScanLine() { } void ScanLine::DDALine(QPainter* painter,int x0,int y0,int x1,int y1) { int x; float dy,dx,k,y; dx=x1-x0; dy=y1-y0; y=y0; k=dy/dx; for(x=x0;x<=x1;x++) { painter->drawPoint(x,int(y+0.5)); y+=k; } painter->drawLine(x0,y0,x1,y1); }以上函数无法被 MainWindow::~MainWindow() { delete ui; } void MainWindow::paintEvent(QPaintEvent *event) { Q_UNUSED(event); QPainter painter(this); // // 反走样 painter.setRenderHint(QPainter::Antialiasing, true); // // 设置画笔颜色 painter.setPen(QColor(0, 160, 230)); // // 绘制直线 //// painter.drawLine(QPointF(ScanLine())); if(menunum==1)//微分绘线 { line=new ScanLine(); line->DDALine(&painter, 30, 10, 10, 30); update(); }调用的解决办法

首先，需要修改ScanLine类的DDALine函数的返回值，让它返回一个QPointF类型的值，表示绘制直线的起点和终点坐标。修改后的代码如下：

#include "scanline.h"
#include <QPointF>

ScanLine::ScanLine() {}

QPointF ScanLine::DDALine(int x0, int y0, int x1, int y1) {
    int x;
    float dy, dx, k, y;
    dx = x1 - x0;
    dy = y1 - y0;
    y = y0;
    k = dy / dx;
    for (x = x0; x <= x1; x++) {
        y += k;
    }
    return QPointF(x0, y0) + QPointF(dx, dy);
}

然后在MainWindow的paintEvent函数中，调用DDALine函数获取绘制直线的起点和终点坐标，再使用QPainter的drawLine函数进行绘制。修改后的代码如下：

void MainWindow::paintEvent(QPaintEvent *event) {
    Q_UNUSED(event);
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing, true);
    painter.setPen(QColor(0, 160, 230));
    if (menunum == 1) {
        line = new ScanLine();
        QPointF end = line->DDALine(30, 10, 10, 30);
        painter.drawLine(QPointF(30, 10), end);
        update();
    }
}

最后，在MainWindow的析构函数中，需要释放line对象的内存，修改后的代码如下：

MainWindow::~MainWindow() {
    delete ui;
    if (line != nullptr) {
        delete line;
    }
}