涂鸦板练习（20200214）

亦凉 2023-07-05 10:23 13阅读 0赞

1. 头文件

#include <QWidget>
    #include <QPainter>
    #include <QMouseEvent>
    #include <QDebug>
    
    class MainWidget : public QWidget
    {
        Q_OBJECT
    
    public:
        MainWidget(QWidget *parent = 0);
        ~MainWidget();
    private:
        QPixmap pix;
        QPoint lastPoint;
        QPoint endPoint;
    protected:
        void paintEvent(QPaintEvent *event);
        void mouseMoveEvent(QMouseEvent *event);
        void mousePressEvent(QMouseEvent *event);
        void mouseReleaseEvent(QMouseEvent *event);
    };

2. cpp文件

#include "mainwidget.h"
    
    MainWidget::MainWidget(QWidget *parent)
        : QWidget(parent)
    {
        resize(600, 500);    //窗口大小设置为600*500
        pix = QPixmap(200, 200);
        pix.fill(Qt::white);
    
    }
    
    MainWidget::~MainWidget()
    {
    
    }
    
    void MainWidget::paintEvent(QPaintEvent *event)
    {
        QPainter pp(&pix);                   // 根据鼠标指针前后两个位置就行绘制直线
        pp.drawLine(lastPoint, endPoint);    // 让前一个坐标值等于后一个坐标值，这样就能实现画出连续的线
        lastPoint = endPoint;
        QPainter painter(this);
        painter.drawPixmap(0, 0, pix);
    }
    
    void MainWidget::mouseMoveEvent(QMouseEvent *event)
    {
        if (event->buttons() == Qt::LeftButton){
            endPoint = event->pos();
            update();
        }
    }
    
    void MainWidget::mousePressEvent(QMouseEvent *event)
    {
        if (event->button() == Qt::LeftButton) {
            lastPoint = event->pos();
        }
    }
    
    void MainWidget::mouseReleaseEvent(QMouseEvent *event)
    {
        if (event->button() == Qt::LeftButton){
            endPoint = event->pos();
            update();
        }
    }

参考资料：

1. [http://shouce.jb51.net/qt-beginning/21.html][http_shouce.jb51.net_qt-beginning_21.html]

2. [mouseMoveEvent中判断鼠标状态][mouseMoveEvent]

[http_shouce.jb51.net_qt-beginning_21.html]: http://shouce.jb51.net/qt-beginning/21.html
[mouseMoveEvent]: https://blog.csdn.net/vXueYing/article/details/86717660