今天写个简单的时钟的程序，秒钟、分钟，时钟能够自动的正确的显示现在的时间，但是不能够修改。这个程序非常简单需要的基本知识是：
1.Qpainter类
2.QTimer
步骤：
1.先新建一个widget
2.重新定义void paintEvent(QPainter *painter)
3.定义一个画图的函数 void draw(QPainter *painter)
main.cpp
#include <QtGui/QApplication>
#include "timer.h"
#include<QTextCodec>
int main(int argc, char *argv[])
{ QApplication a(argc, argv);
QTextCodec::setCodecForTr(QTextCodec::codecForLocale());
Timer w;
w.show();
return a.exec();
}
timer.h
#ifndef TIMER_H
#define TIMER_H
#include <QWidget>
namespace Ui { class Timer;
}
class Timer : public QWidget
{ Q_OBJECT
public:
explicit Timer(QWidget *parent = 0);
~Timer();
void paintEvent(QPaintEvent *);
void draw(QPainter *painter);
private:
Ui::Timer *ui;
};
#endif // TIMER_H
timer.cpp
#include "timer.h"
#include "ui_timer.h"
#include<QtGui>
Timer::Timer(QWidget *parent) :
QWidget(parent),
ui(new Ui::Timer)
{ ui->setupUi(this);
QTimer *timer = new QTimer;//新建一个定时器来定时刷新图
connect(timer,SIGNAL(timeout()),this,SLOT(update()));
timer->start(1000);//每隔1秒钟重新绘制一下
setWindowTitle(tr("深海的小鱼儿"));//定义widget的标题 resize(200,200);//初始固定大小为200x200
}
Timer::~Timer()
{ delete ui;
}
void Timer::paintEvent(QPaintEvent *)
{ QPainter painter(this); //定义一个画笔
painter.setRenderHint(QPainter::Antialiasing);//开启反转使你画的图比较光滑
int side = qMin(width(), height());//取长宽的最小值来作为你放大和缩小的标准值（也就是说你的
painter.translate(width() / 2, height() / 2);//长宽是一样的，这样缩放时不会变形。移到中心点，这时width/height=200
painter.scale(side / 200.0, side / 200.0);
draw(&painter);//开始画图
}
void Timer::draw(QPainter *painter)
{ static const QPoint hourHand[3] = { QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -40)
};//定义时针的图像
static const QPoint minuteHand[3] = { QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -65)
};//定义分针的图像
static const QPoint secondHand[3] = { QPoint(7, 8),
QPoint(-7, 8),
QPoint(0, -85)
};//定义秒针的图像
QColor hourColor(127, 0, 127);//定义时针的颜色
QColor minuteColor(0, 127, 127, 191);//定义分针的颜色
QColor secondColor(0, 0,255);//定义秒针的颜色
QTime time = QTime::currentTime();//取系统的时间
painter->setPen(Qt::NoPen);//开始画秒针的在系统时间的位置
painter->setBrush(secondColor);
painter->save();
painter->rotate(time.second()*6);//360/60=6
painter->drawConvexPolygon(secondHand, 3);
painter->restore();
painter->setPen(Qt::NoPen);//开始画分针的在系统时间的位置
painter->setBrush(hourColor);
painter->save();
painter->rotate(30.0 * ((time.hour() + time.minute() / 60.0)));
painter->drawConvexPolygon(hourHand, 3);
painter->restore();
painter->setPen(hourColor);
for (int i = 0; i < 12; ++i)
{ painter->drawLine(88, 0, 96, 0);
painter->rotate(30.0);
}
painter->setPen(Qt::NoPen);//开始画时针的在系统时间的位置
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);
}