QTmotormeter 程序

#ifndef WIDGET_H
#define WIDGET_H

#include
#include
#include
#include

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();

private:
    Ui::Widget *ui;
    qreal qValues;
    const static int radius;
    const static int maxvelocity;
    const static int minvelocity;
    QTimer *timer;
    bool _isForward;

public:
    void setvalue(qreal iValues);
    void paintEvent(QPaintEvent *event);

private slots:
    void inputValue();

};
#endif // WIDGET_H

---------------------------------------

#include "widget.h"
#include "ui_widget.h"

const int Widget::radius=150;
const int Widget::maxvelocity=400;
const int Widget::minvelocity=0;

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    qValues=0;
    _isForward=true;

    timer=new QTimer(this);
    timer->setInterval(100);
    timer->start();
    connect(timer,&QTimer::timeout,this,&Widget::inputValue);
}

Widget::~Widget()
{
    delete ui;
}

void Widget::setvalue(qreal iValues)
{
    qValues = iValues;
    update();
}

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter painter(this);
    painter.setRenderHint(QPainter::Antialiasing);
    QPoint center(width()/2,height()/2);
    painter.save();

    painter.translate(center);
    painter.setPen(Qt::NoPen);
    painter.setBrush(QColor(142,142,142));
    const int backgroundradius=radius+3;
    painter.drawEllipse(QPoint(),backgroundradius,backgroundradius);

    painter.rotate(-135);
    const int longstep=10;
    const int shortstep=50;

    for(int i=0;i<=shortstep;i++)
    {
        painter.setPen((i

        if (i%(shortstep/longstep)!=0)
        {

            QPoint p1(0,-(radius-8));
            QPoint p2(0,-radius);
            painter.drawLine(p1,p2);
        }
        else
        {
            QPoint p1(0,-(radius-14));
            QPoint p2(0,-radius);
            painter.drawLine(p1,p2);
        }
        painter.rotate(270.0/shortstep);
    }

    painter.restore();
    QFontMetrics fm=painter.fontMetrics();
    int tx=center.x();
    int ty=int(center.y()+(radius/1.4142));

    QString title="yibiaopan";
    QSize tsz=fm.size(0,title);

    QRect trect(QPoint(tx-tsz.width()/2,ty-tsz.height()/2),tsz);
    painter.setPen(QColor(127,127,127));
    painter.setBrush(QColor(173,163,163));
    painter.drawRoundRect(trect.adjusted(-6,-4,6,4),3,3);
    painter.setPen(QColor(243,243,243));
    painter.setBrush(Qt::NoBrush);
    painter.drawText(trect,title);
    painter.setPen(QColor(243,243,243));
    const int hand=radius-21;

    for(int i=0;i<=longstep;i++)
    {
        qreal angle=qDegreesToRadians(-135.0+i*(270.0/longstep));
        QString etext=QString::number(minvelocity+i*(maxvelocity-minvelocity)/longstep);
        QPointF dirvec(qSin(angle),-qCos(angle));
        QPointF ecenter(center.x()+hand*dirvec.x(),center.y()+hand*dirvec.y());
        QSize esz=fm.size(0,etext);
        QRectF erect(QPointF(ecenter.x()-esz.width()/2,ecenter.y()-esz.height()/2),esz);
        painter.drawText(erect,etext);
    }

    painter.save();
    QPoint triangle[]={
        {-5,0},
        {0,25-radius},
        {5,0}
    };

    qreal degree=-135.0+270.0*(qValues-minvelocity)/(maxvelocity-minvelocity);
    painter.translate(center);
    painter.rotate(degree);
    painter.setPen(Qt::NoPen);
    painter.setBrush(Qt::red);
    painter.drawPolygon(triangle,3);
    painter.setPen(QPen(QColor(214,0,0),2));
    painter.drawEllipse(QPoint(),7,7);
    painter.restore();
}

void Widget::inputValue()
{
    if(_isForward)
        qValues+=1;
    else
        qValues-=1;

    if(qValues>=maxvelocity)
    {
        qValues=maxvelocity;
        _isForward=false;
    }
    if(qValues<=minvelocity)
    {
        qValues=minvelocity;
        _isForward=true;
    }

    setvalue(qValues);
}