qt 简单实验创建一个可以拖拽和缩放的矩形

news2024/10/7 0:28:06

1.概要

2.代码

2.1 resizablewidget.h

#ifndef RESIZABLEWIDGET_H
#define RESIZABLEWIDGET_H

#include <QWidget>
#include <QMouseEvent>

class ResizableWidget: public QWidget
{
    Q_OBJECT
public:
    ResizableWidget(QWidget *parent = nullptr);
protected:
    void mousePressEvent(QMouseEvent *event);
    void mouseMoveEvent(QMouseEvent *event);
    void mouseReleaseEvent(QMouseEvent *event);
    void paintEvent(QPaintEvent *event);
private:
    bool resizing;
    QPoint resizeStart;
};

#endif // RESIZABLEWIDGET_H

2.2 resizablewidget.cpp

#include "resizablewidget.h"
#include <QPainter>


ResizableWidget::ResizableWidget(QWidget *parent) : QWidget(parent), resizing(false) {
    // 启用鼠标追踪
    setMouseTracking(true);
}

void ResizableWidget::mousePressEvent(QMouseEvent *event) {
    if (event->button() == Qt::LeftButton) {
        // 检查是否接近右下角
        if (event->pos().x() > width() - 10 && event->pos().y() > height() - 10) {
            resizing = true;
            resizeStart = event->pos();
        }
    }
}

void ResizableWidget::mouseMoveEvent(QMouseEvent *event) {
    if (resizing) {
        int dx = event->x() - resizeStart.x();
        int dy = event->y() - resizeStart.y();

        // 调整控件大小，同时保持位置不变
        resize(width() + dx, height() + dy);

        // 更新起始位置，以便下一次移动
        resizeStart = event->pos();
    }
}

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

void ResizableWidget::paintEvent(QPaintEvent *event)  {
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);
    painter.setBrush(Qt::blue);
    painter.drawRect(rect()); // 绘制一个矩形，其大小由QWidget的size决定
}

2.3 widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui {
class Widget;
}
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

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

private:
    Ui::Widget *ui;
};
#endif // WIDGET_H

2.4 widget.cpp

#include "widget.h"
#include "ui_widget.h"
//#include "resizablerectwidget.h"
#include <QPushButton>
#include "resizablewidget.h"

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    //QPushButton *button = new QPushButton("My Button", this);
    // 设置按钮的位置和大小（可选）
    // 注意：在 QMainWindow 中，你可能需要先设置一个 central widget 或其他容器
    //button->setGeometry(QRect(10, 10, 100, 30));


    //ResizableRectWidget* widget = new ResizableRectWidget(this);
    //widget->setGeometry(100, 100, 200, 100); // 设置初始位置和大小
    //widget.show();

    ResizableWidget* p_rw = new ResizableWidget(this);
    p_rw->setGeometry(0, 0, 200, 100); // 设置初始位置和大小
}

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

2.5 main.cpp

#include "widget.h"
//#include "resizablewidget.h"

#include <QApplication>
//创建一个可以拖拽并且缩放的矩形
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    Widget w;
    w.show();
    //ResizableWidget rw;
    //rw.show();
    return a.exec();
}