013-Qt 事件系统的小案例

auther: abinng date: 2026-05-09 09:36 createDate:2026-05-09 09:36

1. 多功能鼠标操作窗口

目的：了解一下鼠标事件

实现的效果：

• 启动后，改变鼠标默认显示样式，松开和摁下左键的效果
• 双击鼠标左键来使其全屏
• 按着鼠标右键则使指针变为一个自定义的图片
• 可以在界面上按着鼠标左键来拖动窗口
• 使用滚轮可以放大或缩小编辑器中的内容

点击展开

main.cppMouswWidget.hMouseWidget.cpp

#include <QApplication>
#include "MouseWidget.h"

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

#ifndef EX17_MOUSE_MOUSEWIDGET_H
#define EX17_MOUSE_MOUSEWIDGET_H
#include <QWidget>
#include <QTextEdit>

class MouseWidget final : public QWidget {
    Q_OBJECT
public:
    explicit MouseWidget(QWidget* parent = nullptr);
    ~MouseWidget() override = default;
protected:
    void mousePressEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *event) override;
    void mouseDoubleClickEvent(QMouseEvent *event) override;
    void mouseMoveEvent(QMouseEvent *event) override;
    void wheelEvent(QWheelEvent *event) override;
    void closeEvent(QCloseEvent *event) override;
private:
    QPointF offset;
    QTextEdit* edit;
};

#endif //EX17_MOUSE_MOUSEWIDGET_H

#include <QCursor>
#include <QMouseEvent>
#include <QWheelEvent>
#include <QMessageBox>
#include "MouseWidget.h"

#include <QApplication>

MouseWidget::MouseWidget(QWidget *parent) : QWidget(parent) {
    setGeometry(100, 100, 400, 400);
    QCursor cursor;
    cursor.setShape(Qt::OpenHandCursor);
    setCursor(cursor);

    edit = new QTextEdit(this);
    edit->resize(200, 200);
    edit->move(100, 100);
}

void MouseWidget::mousePressEvent(QMouseEvent *event) {
    if (event->button() == Qt::LeftButton) {
        QCursor cursor;
        cursor.setShape(Qt::ClosedHandCursor);
        QApplication::setOverrideCursor(cursor);    // 暂时改变
        offset = event->globalPosition() - pos();
    } else if (event->button() == Qt::RightButton) {
        QPixmap pixmap("./Doraemon.png");
        qreal dpr = qApp->primaryScreen()->devicePixelRatio();
        QSize logicalSize(64, 64);
        QSize realSize = logicalSize * dpr;
        pixmap = pixmap.scaled(realSize, Qt::KeepAspectRatio, Qt::SmoothTransformation);
        pixmap.setDevicePixelRatio(dpr);
        QCursor cursor(pixmap, logicalSize.width(), logicalSize.height());
        QApplication::setOverrideCursor(cursor);
    }
    QWidget::mousePressEvent(event);
}

void MouseWidget::mouseReleaseEvent(QMouseEvent *event) {
    Q_UNUSED(event);
    QApplication::restoreOverrideCursor();      // 恢复鼠标指针
}

void MouseWidget::mouseDoubleClickEvent(QMouseEvent *event) {
    if (event->button() == Qt::LeftButton) {
        if (windowState() != Qt::WindowFullScreen)
            setWindowState(Qt::WindowFullScreen);
        else
            setWindowState(Qt::WindowNoState);
    }
    QWidget::mouseDoubleClickEvent(event);
}

void MouseWidget::mouseMoveEvent(QMouseEvent *event) {
    if (event->buttons() & Qt::LeftButton) {
        QPointF temp = event->globalPosition() - offset;

        move(temp.x(), temp.y());
    }
}

void MouseWidget::wheelEvent(QWheelEvent *event) {
    if (event->angleDelta().y() > 0) {
        edit->zoomIn();
    } else {
        edit->zoomOut();
    }
}

void MouseWidget::closeEvent(QCloseEvent *event) {
    QString title = "鼠标事件框";
    QString info = "确定退出吗？";
    QMessageBox::StandardButton result = QMessageBox::question(this, title, info, QMessageBox::Yes | QMessageBox::No | QMessageBox::Cancel);
    if (result == QMessageBox::Yes) {
        event->accept();
    } else {
        event->ignore();
    }
}

2. 键盘支持和定时器事件

目的：了解一下键盘事件和定时器事件

实现的效果：

• 支持 W, S, A, D 键或上下左右实现按键控件的移动
• 支持Ctrl + Q退出当前主窗口
• 按键上面显示时间，格式为 “mm:ss”

点击展开

main.cppkeyWidget.hkeyWidget.cpp

#include <QApplication>
#include "keyWidget.h"

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

#ifndef EX18_KEYEVENT_KEYWIDGET_H
#define EX18_KEYEVENT_KEYWIDGET_H
#include <QWidget>
#include <QPushButton>

class keyWidget : public QWidget {
public:
    explicit keyWidget(QWidget* parent = nullptr);
    ~keyWidget() override = default;
protected:
    void keyPressEvent(QKeyEvent *event) override;
    void timerEvent(QTimerEvent *event) override;
private:
    QPushButton* btn_move;
    int id1;
    int id2;
};


#endif //EX18_KEYEVENT_KEYWIDGET_H

#include "keyWidget.h"
#include <QKeyEvent>
#include <QTimerEvent>
#include <QTimer>
#include <QTime>

keyWidget::keyWidget(QWidget *parent) : QWidget(parent) {
    setGeometry(100, 100, 400, 400);
    setFocusPolicy(Qt::StrongFocus);
    setFocus();
    btn_move = new QPushButton(this);
    btn_move->resize(80, 80);
    btn_move->setText("Move Button");

    id1 = startTimer(1000);
    id2 = startTimer(2500);
    QTimer *timer = new QTimer(this);
    timer->start(1000);

    connect(timer, &QTimer::timeout, [=]() {
        QTime abc = QTime::currentTime();
        btn_move->setText(abc.toString("mm:ss"));
    });
}

void keyWidget::keyPressEvent(QKeyEvent *event) {
    QPoint pt = btn_move->pos();
    if (event->key() == Qt::Key_A || event->key() == Qt::Key_Left) {
        btn_move->move(pt.x() - 20, pt.y());
    } else if (event->key() == Qt::Key_S || event->key() == Qt::Key_Down) {
        btn_move->move(pt.x(), pt.y() + 20);
    } else if (event->key() == Qt::Key_D || event->key() == Qt::Key_Right) {
        btn_move->move(pt.x() + 20, pt.y());
    } else if (event->key() == Qt::Key_W || event->key() == Qt::Key_Up) {
        btn_move->move(pt.x(), pt.y() - 20);
    } else if (event->modifiers() == Qt::ControlModifier && event->key() == Qt::Key_Q) {
        emit close();
    }
    event->accept();
}

void keyWidget::timerEvent(QTimerEvent *event) {
    static int id1_cnt;
    if (event->timerId() == id1) {
        id1_cnt++;
        qDebug() << "timer1";
        if (id1_cnt == 5) {
            killTimer(id1);
        }
    } else if (event->timerId() == id2) {
        qDebug() << "timer2";
    } else {
        qDebug() << "other timer";
    }
}