Qt实现仪表盘

#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
m_foreground = Qt::magenta;
m_background = Qt::black;
m_title = "温度";
m_startAngle = 45;
m_endAngle = 45;
m_scaleMajor = 10;
m_minValue = 0;
m_maxValue = 50;
m_scaleMinor = 5;
m_value = 0;

}

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

void MainWindow::paintEvent(QPaintEvent *)
{
QPainter painter(this);
QFont font("宋体", 14);
painter.setFont(font);
painter.setRenderHint(QPainter::Antialiasing);
painter.translate(width() / 2, height() / 2);           
//坐标变换为窗体中心
int side = qMin(width(), height());
painter.scale(side / 400.0, side / 400.0);              
//比例缩放
drawCrown(&painter);                                    
//画表盘边框
drawScaleNum(&painter);                                 
//画刻度数值
drawScale(&painter);                                    
//画刻度线
drawTitle(&painter);                                    
//画单位
//    drawNumericValue(&painter);                             
//画数字显示
drawIndicator(&painter);
}

void MainWindow::drawCrown(QPainter *painter)
{
painter->save();
int radius = 200;
painter->setBrush(m_background = QColor(20,20,20));
QLinearGradient lg1(0, -220, 0, 220);
lg1.setColorAt(0, Qt::darkCyan);
lg1.setColorAt(1, QColor(20, 20, 20));
painter->setBrush(lg1);
painter->setPen(Qt::NoPen);
painter->drawEllipse(-radius, -radius, radius << 1, radius <<1);
painter->setBrush(m_background = QColor(20, 20, 20));
painter->drawEllipse(-180, -180, 360, 360);
painter->restore();
}

void MainWindow::drawTitle(QPainter *painter)
{
painter->save();
painter->setPen(QColor(220,200,200,200));
QString str(m_title);
QFontMetricsF fm(this->font());
painter->drawText(-30, -50, str);
painter->restore();
}

void MainWindow::drawScaleNum(QPainter *painter)
{
painter->save();
painter->setPen(QPen(QColor(255,255,255)));
QFontMetricsF fm(this->font());
int radius = 200;
int r=(int)(radius*0.8);
int Angle=45;
int gap = (360-Angle*2) / 10;
for(int i=0; i<=10; i+=1)
    {
int angle = 90+Angle+gap*i;                                 //角度,每隔10格子画一个刻度值
float angleArc =( angle % 360) * 3.14159 / 180;                //转换为弧度
int x = (r)*cos(angleArc);
int y = (r)*sin(angleArc);
QString value =QString( "%1" ).arg(i*5);
//字体大小及位置要微调
int h = fm.size(Qt::TextSingleLine,value).height();
x = x -10;
y = y + h/2;
painter->drawText(QPointF(x, y),value);
    }
painter->restore();
}

void MainWindow::drawScale(QPainter *painter)
{
painter->save();
painter->rotate(m_startAngle);
int steps = (m_scaleMajor * m_scaleMinor);                          //总刻度数量
double angleStep = (360.0 - m_startAngle - m_endAngle) / steps;     //每一个份数的角度
for (int i = 0; i <= steps; i++)
    {
if (i % m_scaleMinor == 0)                                      //大刻度
        {
QPen pen ;
pen.setColor(Qt::lightGray);
pen.setWidth(2);
painter->setPen(pen);
painter->drawLine(0, 125, 0, 145);
        }
else                                                            //小刻度
        {
QPen pen ;
pen.setColor(Qt::darkGray);
pen.setWidth(1);
painter->setPen(pen);
painter->drawLine(0, 125, 0, 135);
        }
painter->rotate(angleStep);
    }
painter->restore();
}

void MainWindow::drawIndicator(QPainter *painter)
{
painter->save();
QPolygon pts;
pts.setPoints(5, -2,0, -4,30, 0,120, 4,30, 2,0);            
//第一个参数是坐标的个数，记下来是坐标
painter->rotate(m_startAngle);
double degRotate =  (360.0 - m_startAngle - m_endAngle)/(m_maxValue - m_minValue)*(m_value - m_minValue);

//画指针
painter->rotate(degRotate);                                

//顺时针旋转坐标系统
QRadialGradient haloGradient(0, 0, 60, 0, 0);               
//辐射渐变
haloGradient.setColorAt(0, QColor(60,60,60));
haloGradient.setColorAt(1, QColor(160,160,160));
painter->setPen(Qt::yellow);                                 
//定义线条文本颜色  设置线条的颜色
painter->setBrush(haloGradient);                           
//刷子定义形状如何填满 填充后的颜色
painter->drawConvexPolygon(pts);
painter->restore();
//画中心点
QColor niceBlue(150, 150, 200);
QConicalGradient coneGradient(0, 0, -90.0);                 
//角度渐变
coneGradient.setColorAt(0.0, Qt::darkGray);
coneGradient.setColorAt(0.2, niceBlue);
coneGradient.setColorAt(0.5, Qt::yellow);
coneGradient.setColorAt(1.0, Qt::darkGray);
painter->setPen(Qt::NoPen);
painter->setBrush(coneGradient);
painter->drawEllipse(-8, -8, 16, 16);
}