使用QT绘图和绘图事件，完成仪表盘绘图，如下图：

 程序运行结果：

 

代码：

widget.h

#ifndef WIDGET_H
#define WIDGET_H#include <QWidget>
#include <QPainter>
#include <QPen>
#include <QBrush>
#include <QDebug>QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACEclass Widget : public QWidget
{Q_OBJECTpublic:Widget(QWidget *parent = nullptr);~Widget();void paintEvent(QPaintEvent *event) override;public slots:void horizontalSliderValueChanged(int);private:Ui::Widget *ui;
};
#endif // WIDGET_H

widget.cpp

#include "widget.h"
#include "ui_widget.h"Widget::Widget(QWidget *parent): QWidget(parent), ui(new Ui::Widget)
{ui->setupUi(this);ui->horizontalSlider->setValue(0);ui->horizontalSlider->setMinimum(0);ui->horizontalSlider->setMaximum(280);connect(ui->horizontalSlider,SIGNAL(valueChanged(int)), this, SLOT(horizontalSliderValueChanged(int)));
}Widget::~Widget()
{delete ui;
}void Widget::paintEvent(QPaintEvent *event)
{//QPainter p (this);QPen pen;QBrush brush;p.translate(this->width()/2,this->height()/2);//p.setPen(Qt::NoPen);//画外部圆brush.setColor(QColor(100,100,100));brush.setStyle(Qt::SolidPattern);p.setBrush(brush);p.drawEllipse(-150,-150,300,300);//画内部圆brush.setColor(QColor(60,60,60));p.setBrush(brush);p.drawEllipse(-140,-140,280,280);//画蓝色圈brush.setColor(QColor(0,105,210));p.setBrush(brush);p.drawEllipse(-40,-40, 80, 80);//画中心圆brush.setColor(QColor(60,60,60));p.setBrush(brush);p.drawEllipse(-20,-20,40,40);brush.setColor(QColor(0,255,255));p.setBrush(brush);p.drawEllipse(-5,-5,10,10);//画刻度pen.setWidth(3);pen.setStyle(Qt::SolidLine);p.rotate(130);for (int i = 0; i <= 40; i++ ) {pen.setColor(QColor(255,240-i*6,0));p.setPen(pen);if(i%2 == 0){p.drawLine(130,0,115,0);}else{p.drawLine(130,0,120,0);}p.rotate(7);}//画指针p.rotate(73);p.rotate(ui->horizontalSlider->value());pen.setColor(QColor(0,255,255));p.setPen(pen);p.drawLine(106,0,0,0);}void Widget::horizontalSliderValueChanged(int)
{//通知，整个窗口重绘this->update();
}

widget.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0"><class>Widget</class><widget class="QWidget" name="Widget"><property name="geometry"><rect><x>0</x><y>0</y><width>400</width><height>400</height></rect></property><property name="minimumSize"><size><width>400</width><height>400</height></size></property><property name="windowTitle"><string>仪表盘</string></property><widget class="QSlider" name="horizontalSlider"><property name="geometry"><rect><x>100</x><y>370</y><width>200</width><height>20</height></rect></property><property name="orientation"><enum>Qt::Horizontal</enum></property></widget></widget><resources/><connections/>
</ui>