授人以鱼不如授人以渔-圆形刻度盘或者进度条各种计算公式 - QTCN开发网

网上实在找不到计算公式，下面是我动手制作过程中摸索出来的，不准的地方望海涵，有了这公式，刻度盘，进度条随你搞，哈哈哈哈！
遇到事情还是要多动手！！！
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#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QLabel>
#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();
    void paintEvent(QPaintEvent *event);
private:
    Ui::MainWindow *ui;
    QLabel    *l1;
    QLabel    *l2;
    QLabel    *l3;
};

#endif // MAINWINDOW_H

#include "mainwindow.h"
#include "ui_mainwindow.h"

#include <QPainter>
//当前值
const int u =43;
//最大刻度
const int nMax = 100;
//最小刻度
const int nMin = 0;
//旋转角度
const double nPercentRotate = 40;
//
const int nMaxRadus = 200;

const int nMinRadus = 150;

const int nDistance = 50;
//最外面的大圆
const int nDistance2 = 70;
//原点
int nOrgXpos     = 0;
int nOrgYpos     = 0;

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

    nOrgXpos = width() / 2;

    nOrgYpos = height() / 2;

    l1 = new QLabel(this);

    l1->setText(QString("44"));

    l1->move(nOrgXpos   ,nOrgYpos );

    l2 = new QLabel(this);

    l3 = new QLabel(this);

    l2->setText(QString("Min"));
    //这个地方要注意
    l2->move(nOrgXpos - nMinRadus, nOrgYpos + nMinRadus );

    l3->setText(QString("Max"));

    l3->move(nOrgXpos  + (nMinRadus ) , nOrgYpos +  (nMinRadus ) );

}

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

void MainWindow::paintEvent(QPaintEvent *event)
{
    QColor use(112,222,121);
    QColor nouse(223,123,111);
    QPainter p(this);
    double nRotate = (360.0 - 2 * nPercentRotate) / (nMax - nMin);
    p.setRenderHint(QPainter::Antialiasing);
    p.setRenderHint(QPainter::SmoothPixmapTransform);

    p.save();
    p.translate(nOrgXpos, nOrgYpos);
    p.rotate(nPercentRotate);
    p.setPen(use);
    for(int i = 0 ; i < u; i++){

        p.drawLine(0,nMinRadus,0,nMaxRadus);
        p.rotate(nRotate);
    }
    p.setPen(nouse);
    for(int i = u ; i < nMax ; i++){

        p.drawLine(0,nMinRadus,0,nMaxRadus);
        p.rotate(nRotate);
    }
    p.restore();

    p.setPen(QColor(11,22,33));
    p.drawEllipse(nOrgXpos - nMinRadus + nDistance/2  , nOrgYpos  - nMinRadus  + nDistance/2   , nMinRadus * 2 - nDistance , nMinRadus * 2 - nDistance );

    p.restore();
    p.setPen(QColor(11,22,33));
    p.drawEllipse(nOrgXpos -  nMaxRadus - nDistance2/2  , nOrgYpos  -  nMaxRadus -  nDistance2/2 , nMaxRadus * 2 + nDistance2, nMaxRadus * 2 + nDistance2);
}