void MainWindow::mousePressEvent(QMouseEvent* event)//鼠標設置障礙物起始，終點 { if(event->button()==Qt::LeftButton&&mode==0)//障礙物 { int j=(event->y()-50)/25-1,i=(event->x()-200)/25; _MAP[i][j]=!_MAP[i][j]; update(); }，將鼠標點擊變爲框選完整代碼

完整代码如下：

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QMouseEvent>
#include <QPainter>

const int MAP_WIDTH = 20;
const int MAP_HEIGHT = 20;

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

    setFixedSize(600, 600);
    setWindowTitle("A* Path Finding");

    mode = 0;
    isSelecting = false;
    memset(_MAP, 0, sizeof(_MAP));
}

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

void MainWindow::mousePressEvent(QMouseEvent* event)
{
    if (event->button() == Qt::LeftButton && mode == 0)
    {
        int j = (event->y() - 50) / 25 - 1;
        int i = (event->x() - 200) / 25;
        // 判断鼠标是否在地图区域内
        if (i >= 0 && i < MAP_WIDTH && j >= 0 && j < MAP_HEIGHT)
        {
            // 记录下鼠标的起点，并将 isSelecting 标记为 true
            startPoint = endPoint = QPoint(i, j);
            isSelecting = true;
            update();
        }
    }
}

void MainWindow::mouseMoveEvent(QMouseEvent* event)
{
    if (isSelecting)
    {
        int j = (event->y() - 50) / 25 - 1;
        int i = (event->x() - 200) / 25;
        // 判断鼠标是否在地图区域内
        if (i >= 0 && i < MAP_WIDTH && j >= 0 && j < MAP_HEIGHT)
        {
            // 记录下鼠标的终点，并调用 update 函数进行界面更新
            endPoint = QPoint(i, j);
            update();
        }
    }
}

void MainWindow::mouseReleaseEvent(QMouseEvent* event)
{
    if (event->button() == Qt::LeftButton && mode == 0 && isSelecting)
    {
        // 标记为框选结束
        isSelecting = false;

        // 获取框选的矩形
        int left = qMin(startPoint.x(), endPoint.x());
        int top = qMin(startPoint.y(), endPoint.y());
        int right = qMax(startPoint.x(), endPoint.x());
        int bottom = qMax(startPoint.y(), endPoint.y());

        // 将框选的矩形内的格子设置为障碍物
        for (int i = left; i <= right; i++)
        {
            for (int j = top; j <= bottom; j++)
            {
                if (i >= 0 && i < MAP_WIDTH && j >= 0 && j < MAP_HEIGHT)
                {
                    _MAP[i][j] = true;
                }
            }
        }

        update();
    }
}

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

    // 绘制地图
    painter.setPen(Qt::black);
    painter.setBrush(Qt::white);
    for (int i = 0; i < MAP_WIDTH; i++)
    {
        for (int j = 0; j < MAP_HEIGHT; j++)
        {
            if (_MAP[i][j])
            {
                painter.fillRect(QRect(i * 25 + 200, j * 25 + 50, 25, 25), Qt::black);
            }
            else
            {
                painter.drawRect(QRect(i * 25 + 200, j * 25 + 50, 25, 25));
            }
        }
    }

    // 绘制框选的矩形
    if (isSelecting)
    {
        painter.setPen(Qt::red);
        painter.setBrush(Qt::NoBrush);
        painter.drawRect(QRect(startPoint, endPoint));
    }
}

这个代码实现了在地图上鼠标框选多个格子，并将其设置为障碍物的功能。你可以在窗口中按下鼠标左键并拖动鼠标来进行框选。