QTday4

作业

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPainter>
#include <QPen>
#include <QColorDialog>
#include <QMouseEvent>
#include <QVector>
#include <QKeyEvent>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE


// 定义 LineInfo 结构体
struct LineInfo {
    QLine line;
    QColor color;
    int width;
};

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

private:
    Ui::Widget *ui;
    QPen pen;
    QPoint start;
    QPoint end;
    QColor color;
    QColor precolor;
    int width;

    QVector<LineInfo> lines;  // 保存所有线段
    bool iser = false;

protected:
    virtual void paintEvent(QPaintEvent *event) override;
    virtual void mouseMoveEvent(QMouseEvent *event) override;
    virtual void mousePressEvent(QMouseEvent *event) override;
    virtual void mouseReleaseEvent(QMouseEvent *event) override;

    virtual void keyPressEvent(QKeyEvent *event)override;

private slots:
    void on_pushButton_clicked();  // 打开调色板
    void on_pushButton_2_clicked(); // 设置线宽为1
    void on_pushButton_3_clicked(); // 设置线宽为5
    void on_pushButton_4_clicked(); // 设置线宽为10
    void on_pushButton_5_clicked();
};

#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    color = Qt::black;  // 默认颜色为黑色
    width = 1;          // 默认线宽为1
}

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

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

    // 遍历所有线段并绘制
    for (auto perline : lines) {
        // 设置当前线段的颜色和宽度
        painter.setPen(QPen(perline.color, perline.width));

        // 绘制线段
        painter.drawLine(perline.line);
    }
}

void Widget::mouseMoveEvent(QMouseEvent *event)
{
    if (event->buttons() & Qt::LeftButton) {
        end = event->pos();


        QLine line(start, end);  // 设置线段

        lines.append({line,color,width});      // 设置颜色




        start = end;  // 更新起点
        update();     // 触发重绘
    }
}

void Widget::mousePressEvent(QMouseEvent *event)
{
    if (event->button() == Qt::LeftButton) {
        start = event->pos();  // 记录起点
    }
}

void Widget::mouseReleaseEvent(QMouseEvent *event)
{

    end = event->pos();
}

void Widget::keyPressEvent(QKeyEvent *event)
{
    if (event->modifiers()==Qt::ControlModifier && event->key() == Qt::Key_Z) {
         if (!lines.isEmpty()) {
             lines.pop_back(); // 删除最后一条线段
             update(); // 触发重绘
         }
     } else {
         QWidget::keyPressEvent(event); // 调用基类的 keyPressEvent 处理其他按键事件
     }
}

// 打开调色板
void Widget::on_pushButton_clicked()
{
    color = QColorDialog::getColor(Qt::black, this, "选择颜色");
}

void Widget::on_pushButton_2_clicked()
{
    width = 1;
}

void Widget::on_pushButton_3_clicked()
{
    width = 5;
}

void Widget::on_pushButton_4_clicked()
{
    width = 10;
}

void Widget::on_pushButton_5_clicked()
{
    iser = !iser;
    if(iser){
           // 进入橡皮擦模式，保存当前颜色并将画笔颜色设置为窗口背景色
           precolor = color;
           // 橡皮擦设置为背景色
           color = palette().color(QPalette::Window);
           // 按钮文字状态改为“切换到画笔”
           ui->pushButton_5->setText("切换到画笔");
       }else{
           // 退出橡皮擦模式，恢复画笔颜色为之前保存的颜色
           color = precolor;
           // 按钮文字状态改为“橡皮擦”
           ui->pushButton_5->setText("橡皮擦");
       }
}