基於QT5實現一個時鐘桌面

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++11

# You can make your code fail to compile if it uses deprecated APIs.
# In order to do so, uncomment the following line.
#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0

SOURCES += \
    main.cpp \
    analogclock.cpp

HEADERS += \
    analogclock.h

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

#ifndef ANALOGCLOCK_H
#define ANALOGCLOCK_H

#include <QWidget>

class AnalogClock : public QWidget
{
    Q_OBJECT

public:
    AnalogClock(QWidget *parent=0);
protected:
    void paintEvent(QPaintEvent *event) override;
};
#endif // WIDGET_H

#include <QtWidgets>
#include "analogclock.h"
AnalogClock::AnalogClock(QWidget *parent)
    : QWidget(parent)
{
    QTimer *timer = new QTimer(this);
    //實例一個QTimer的類
    connect(timer, SIGNAL(timeout()), this, SLOT(update()));
    //監控timeout（）信號是否發出
    //timeout()表示：This signal is emitted when the timer times out.
    //指計時器發出信號，即下面的延時器發出信號
    timer->start(1000);//設置1s的延時
   /*
    *for a function
    * void QTimer::start(int msec)
    * Starts or restarts the timer with a timeout interval of msec milliseconds.
    * If the timer is already running, it will be stopped and restarted.
    * If singleShot is true, the timer will be activated only once.
    * 單位是毫秒，表示每一秒設置一個信號發出
    */
    setWindowTitle(tr("Analog Clock"));
    //void setWindowTitle(const QString &)
    resize(200, 200);
    //初始值大小
}
void AnalogClock::paintEvent(QPaintEvent *)
 {
    /*
     *
     *   repaint() or update() was invoked,
     *   the widget was obscured and has now been uncovered, or
     *   many other reasons.
     *
     *
     */
    static const QPoint hourHand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -40)
    };//用於繪制時針的三角形
    static const QPoint minuteHand[3] = {
        QPoint(7, 8),
        QPoint(-7, 8),
        QPoint(0, -60)
    };//用於繪制分針的三角形
    static const QPoint secondHand[3]={
        QPoint(7,8),
        QPoint(-7,8),
        QPoint(0,-90)
    };//用於繪制秒針的三角形

    QColor hourColor(127, 0, 127);
    QColor minuteColor(0, 127, 127, 191);
    //QColor::QColor(int r, int g, int b, int a = 255)a表示透明度
    QColor secondColor(220,20,60,100);
    //為每一個圖形繪制顏色及透明度

    int side = qMin(width(), height());
    //我認為這一句的作用在於找到最小標出，用於坐標系的繪制

    QTime time = QTime::currentTime();
    qDebug()<<time<<'\n';//用於檢驗現在的時間

    QPainter painter(this);//Qt強大的畫圖工具
    painter.setRenderHint(QPainter::Antialiasing);// 用於反鋸齒
    //針對所有的組件，都反鋸齒//表示設置渲染提示

    painter.translate(width() / 2, height() / 2);//將原點放在中心
    painter.scale(side / 200.0, side / 200.0);//Scales the coordinate system by (sx, sy).標尺坐標系
    //Qt畫板的x和y表示什麼，x表示橫線嗎，y表示縱線嗎？對的
    //說明橫坐標的范圍是-100到100
    //   縱坐標的范圍是-100到100

//時針：
    painter.setPen(Qt::NoPen);//一般用於描邊，Qt::NoPen表示畫筆沒有邊界
    painter.setBrush(hourColor);//一般用於填充

    //先將原先的painter存儲起來，對目前的painter操作，目前的操作不對原本的產生影響，即原本不旋轉
    painter.save();//首先將原先畫筆類似於入棧，對另一個畫筆操作
    painter.rotate(30.0 * ((time.hour() + time.minute() / 60.0)));//表示旋轉，若缺少painter.save(),會對整個painter類旋轉
    painter.drawConvexPolygon(hourHand, 3);//繪制多邊形
    painter.restore();//與painter.save()配套使用


    painter.setPen(hourColor);

    for (int i = 0; i < 12; ++i) {
        painter.drawLine(88, 0, 96, 0);
        painter.rotate(30.0);//畫橫線，表示時間示數的標尺
    }//分針和秒針同時針

//分針：
    painter.setPen(Qt::NoPen);
    painter.setBrush(minuteColor);

    painter.save();
    painter.rotate(6.0 * (time.minute() + time.second() / 60.0));
    painter.drawConvexPolygon(minuteHand, 3);
    painter.restore();

    painter.setPen(minuteColor);
    for (int j = 0; j < 60; ++j) {
        if ((j % 5) != 0)
            painter.drawLine(92, 0, 96, 0);
        painter.rotate(6.0);
    }

//時針：
    painter.setPen(Qt::NoPen);
    painter.setBrush(secondColor);

    painter.save();
    painter.rotate(6*time.second());
    painter.drawConvexPolygon(secondHand,3);
    painter.restore();


}

#include "analogclock.h"

#include <QApplication>

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