要求：使用QT绘图，完成仪表盘绘制，如下图。

素材

 

 运行效果：

代码： 

widget.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QPainter>
#include <QPen>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
    void paintEvent(QPaintEvent *event) override;

public slots:
    void horizontalSliderValueChangedSlot(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->setMaximum(100);
    ui->horizontalSlider->setMinimum(0);

    connect(ui->horizontalSlider, SIGNAL(valueChanged(int) ), this, SLOT(horizontalSliderValueChangedSlot(int)));
}

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

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter p(this);

    double R  = this->width()*0.375;

    p.translate(this->width()/2,this->height()/2);


    p.drawPixmap(-R*1.01,-R*0.98,2*R,2*R,QPixmap(":/rs/Pan.png"));

    p.rotate(ui->horizontalSlider->value() * 2.8 + 130);
    p.drawPixmap(-R*0.08,-R*0.085,R*0.72,R*0.15,QPixmap(":/rs/Point.png"));

}

void Widget::horizontalSliderValueChangedSlot(int)
{
    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="sizeIncrement">
   <size>
    <width>0</width>
    <height>0</height>
   </size>
  </property>
  <property name="baseSize">
   <size>
    <width>0</width>
    <height>0</height>
   </size>
  </property>
  <property name="windowTitle">
   <string>仪表盘</string>
  </property>
  <layout class="QVBoxLayout" name="verticalLayout">
   <property name="leftMargin">
    <number>100</number>
   </property>
   <property name="topMargin">
    <number>10</number>
   </property>
   <property name="rightMargin">
    <number>100</number>
   </property>
   <property name="bottomMargin">
    <number>10</number>
   </property>
   <item>
    <spacer name="verticalSpacer">
     <property name="orientation">
      <enum>Qt::Vertical</enum>
     </property>
     <property name="sizeHint" stdset="0">
      <size>
       <width>20</width>
       <height>40</height>
      </size>
     </property>
    </spacer>
   </item>
   <item>
    <widget class="QSlider" name="horizontalSlider">
     <property name="orientation">
      <enum>Qt::Horizontal</enum>
     </property>
    </widget>
   </item>
  </layout>
 </widget>
 <resources/>
 <connections/>
</ui>