C++版QT：电子时钟

digiclock.h

#ifndef DIGICLOCK_H
#define DIGICLOCK_H
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#include <QLCDNumber>
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class DigiClock : public QLCDNumber
{
    Q_OBJECT
public:
    DigiClock(QWidget* parent = 0);
    void mousePressEvent(QMouseEvent*);
    void mouseMoveEvent(QMouseEvent*);
public slots:
    void showTime();                   //显示当前的时间
private:
    QPoint dragPosition;              //保存鼠标点相对电子时钟窗体左上角的偏移值
    bool showColon;                    //用于显示时间时是否显示“：”
};
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#endif // DIGICLOCK_H
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digiclock.cpp

#include "digiclock.h"
#include <QTimer>
#include <QTime>
#include <QMouseEvent>
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DigiClock::DigiClock(QWidget* parent)
    :QLCDNumber(parent)
{
    QPalette p = palette();
    p.setColor(QPalette::Window, Qt::blue);
    setPalette(p);
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    setWindowFlags(Qt::FramelessWindowHint);
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    setWindowOpacity(0.5);
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    QTimer* timer = new QTimer(this);
    connect(timer, SIGNAL(timeout()), this, SLOT(showTime()));
    timer->start(1000);
    showTime();
    resize(150, 60);
    showColon = true;                                 //初始化
}
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void DigiClock::showTime()
{
    QTime time = QTime::currentTime();
    QString text = time.toString("hh:mm");
    if (showColon)
    {
        text[2] = ':';
        showColon = false;
    }
    else
    {
        text[2] = ' ';
        showColon = true;
    }
    display(text);
}
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void DigiClock::mousePressEvent(QMouseEvent* event)
{
    if (event->button() == Qt::LeftButton)
    {
        dragPosition = event->globalPos() - frameGeometry().topLeft();
        event->accept();
    }
    if (event->button() == Qt::RightButton)
    {
        close();
    }
}
void DigiClock::mouseMoveEvent(QMouseEvent* event)
{
    if (event->buttons() & Qt::LeftButton)
    {
        move(event->globalPos() - dragPosition);
        event->accept();
    }
}
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main.cpp

#include <QApplication>
#include "digiclock.h"
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int main(int argc, char* argv[])
{
    QApplication a(argc, argv);
    DigiClock clock;
    clock.show();
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    return a.exec();
}
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