QT时钟绘制

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include<QRect>
#include<QDateTime>
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    this->drawpixmap();//先画画布，再初始化窗口
    ui->setupUi(this);

    this->setWindowTitle(tr("Deom"));
    timer=new QTimer(this);
    timer->start(1000);//每秒触发一次
    connect(timer,SIGNAL(timeout()),this,SLOT(update()));
}

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

void MainWindow::paintEvent(QPaintEvent *event)
{
    //手动双缓冲
    QPainter paint(this);
    paint.setRenderHint(QPainter::Antialiasing,true);//反走样处理打开
    //在50，50的位置画入画布/所以圆点位置在窗口的160，160
    paint.drawPixmap(50,50,*pix);
    recttext=new QRect(50,50,220,220);

    QTime time=QDateTime::currentDateTime().time();
    int hour=time.hour();
    int minute=time.minute();
    int second=time.second();

    if(hour>12)
    {
        paint.drawText(*recttext,Qt::AlignTop|Qt::AlignHCenter,"PM");

    }
    else
    {
        paint.drawText(*recttext,Qt::AlignTop|Qt::AlignHCenter,"AM");
    }

    QTransform transformminute;
    //以圆点坐标160，160做旋转中心
    //画时分秒针
    transformminute.translate(160,160);
    transformminute.rotate(minute*6+0.1*second);
    paint.setTransform(transformminute);
    paint.drawLine(-0,-80,0,0);



    QTransform transformsecond;
    transformsecond.translate(160,160);
    transformsecond.rotate(6*second);
    paint.setTransform(transformsecond);
    paint.drawLine(-0,-60,0,0);

    QTransform transformhour;
    transformhour.translate(160,160);
    transformhour.rotate(30*hour+0.5*minute);//忽略秒对时针的摆
    paint.setTransform(transformhour);
    paint.drawLine(-0,-40,0,0);

}





void MainWindow::drawpixmap()
{
    //画布大小220*220
    pix=new QPixmap(220,220);
    //用窗口背景色填充画布背景
    pix->fill(this->palette().background().color());
    QPainter paint(pix);
    paint.setRenderHint(QPainter::Antialiasing,true);//反走样处理打开
    //画圆
    //圆心为110，110
    paint.drawEllipse(10,10,200,200);
    //这个rect适用于旋转和画数字刻度的
    QRect* rect=new QRect(-30,-90,60,20);
    QTransform tran;
    //以圆心为旋转中心
    tran.translate(110,110);
    for(int i=1;i<=12;i++)
    {
        //总共12个刻度，12段，每段30度
        tran.rotate(30);
        paint.setTransform(tran);
        //绘制数字刻度，垂直最上，水平居中，
        paint.drawText(*rect,Qt::AlignTop|Qt::AlignHCenter,QString::number(i));
        //绘制线条刻度,
        paint.drawLine(0,-100,0,-92);
    }
    //画圆点
    paint.setBrush(Qt::black);
    paint.drawEllipse(-1,-1,2,2);

}

QPainter paint(this);

QTransform transformsecond;

transformsecond.translate(160,160);

 transformsecond.rotate(30);

 paint.setTransform(transformsecond);

paint.drawLine(0,-60,0,0);