可以在主窗口中绘制100*100网格吗，去掉背景色-QT开发中文网

当然可以。你可以通过重写paintEvent方法来在主窗口的画布中绘制一个100x100的网格，并去掉背景色。以下是修改后的代码示例：

#include <QApplication>
#include <QMainWindow>
#include <QScrollArea>
#include <QFrame>
#include <QVBoxLayout>
#include <QPainter>
#include <QMouseEvent>

class CanvasFrame : public QFrame {
    Q_OBJECT

public:
    CanvasFrame(QWidget *parent = nullptr) : QFrame(parent) {
        setMinimumSize(500, 500);
        setMouseTracking(true); // 启用鼠标跟踪
    }

protected:
    void paintEvent(QPaintEvent *event) override {
        Q_UNUSED(event);
        
        QPainter painter(this);
        
        // 设置线条颜色和宽度
        painter.setPen(QPen(Qt::gray, 1));

        int gridSize = 100;
        
        // 绘制横向网格线
        for (int i = 0; i <= height(); i += gridSize) {
            painter.drawLine(0, i, width(), i);
        }
        
        // 绘制纵向网格线
        for (int j = 0; j <= width(); j += gridSize) {
            painter.drawLine(j, 0, j, height());
        }
    }

    void mousePressEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            lastMousePos = event->pos();
            dragging = true;
        }
    }

    void mouseMoveEvent(QMouseEvent *event) override {
        if (dragging) {
            int dx = event->pos().x() - lastMousePos.x();
            int dy = event->pos().y() - lastMousePos.y();
            
            horizontalScrollBar()->setValue(horizontalScrollBar()->value() - dx);
            verticalScrollBar()->setValue(verticalScrollBar()->value() - dy);

            lastMousePos = event->pos();
        }
    }

    void mouseReleaseEvent(QMouseEvent *event) override {
        if (event->button() == Qt::LeftButton) {
            dragging = false;
        }
    }

private:
    QPoint lastMousePos;
    bool dragging = false;
};

class MainWindow : public QMainWindow {
public:
    MainWindow(QWidget *parent = nullptr)
      : QMainWindow(parent)
    {
       setWindowTitle("Grid Example");
       resize(800, 600);

       auto layout = new QVBoxLayout;

       auto leftFrame = new QFrame(this);
       leftFrame->setFixedWidth(200);
       leftFrame->setStyleSheet("background-color: green;");

       auto scrollArea = new QScrollArea(this);
       auto canvas = new CanvasFrame(scrollArea);

       scrollArea->setWidget(canvas);
       scrollArea->setWidgetResizable(true);

       layout->addWidget(leftFrame);
       layout->addWidget(scrollArea);

       QWidget *centralWidget = new QWidget(this);
       centralWidget->setLayout(layout);
       setCentralWidget(centralWidget);
   }
};

int main(int argc, char *argv[]) {
   QApplication a(argc, argv);
   MainWindow w;
   w.show();
   return a.exec();
}