以下是用Qt实现漂亮预警仪表的步骤和代码：

1. 创建一个Qt项目，并添加一个主窗口。

2. 在主窗口中添加QGraphicsView控件，用于绘制预警仪表。

3. 创建一个QGraphicsScene对象，并将其设置为QGraphicsView的场景。

   QGraphicsScene *scene = new QGraphicsScene(this);
   ui->graphicsView->setScene(scene);
   

4. 创建一个QGraphicsEllipseItem对象，用于表示预警仪表的外框。

   QGraphicsEllipseItem *outerCircle = new QGraphicsEllipseItem(QRectF(-120,-120,240,240));
   outerCircle->setPen(QPen(Qt::black, 4));
   scene->addItem(outerCircle);
   

5. 创建一个QGraphicsEllipseItem对象，用于表示预警仪表的中心点。

   QGraphicsEllipseItem *centerCircle = new QGraphicsEllipseItem(QRectF(-15,-15,30,30));
   centerCircle->setBrush(QBrush(Qt::red));
   centerCircle->setPen(QPen(Qt::black, 2));
   centerCircle->setZValue(1);
   scene->addItem(centerCircle);
   

6. 创建一些QGraphicsLineItem对象，用于表示预警仪表的刻度线。

   for (int i = 0; i < 12; i++) {QGraphicsLineItem *line = new QGraphicsLineItem(-100, 0, -80, 0);line->setPen(QPen(Qt::black, 3));line->setRotation(i * 30);line->setPos(0, 0);scene->addItem(line);
   }
   

7. 创建一个QGraphicsPolygonItem对象，用于表示预警仪表的指针。

   QPolygonF polygon;
   polygon << QPointF(-10, 0) << QPointF(0, -120) << QPointF(10, 0);
   QGraphicsPolygonItem *pointer = new QGraphicsPolygonItem(polygon);
   pointer->setBrush(QBrush(Qt::red));
   pointer->setPen(QPen(Qt::black, 2));
   pointer->setZValue(2);
   pointer->setPos(0, 0);
   scene->addItem(pointer);
   

8. 在主窗口的定时器中更新指针的旋转角度。

   void MainWindow::timerEvent(QTimerEvent *event)
   {Q_UNUSED(event);int angle = ui->spinBox->value();QGraphicsItem *item = ui->graphicsView->scene()->items().at(3);item->setRotation(angle);
   }
   

完整的代码如下：

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H#include 
#include 
#include 
#include 
#include QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACEclass MainWindow : public QMainWindow
{Q_OBJECTpublic:MainWindow(QWidget *parent = nullptr);~MainWindow();protected:void timerEvent(QTimerEvent *event);private:Ui::MainWindow *ui;QGraphicsScene *scene;QGraphicsEllipseItem *outerCircle;QGraphicsEllipseItem *centerCircle;QGraphicsPolygonItem *pointer;QList lines;
};
#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget *parent): QMainWindow(parent), ui(new Ui::MainWindow)
{ui->setupUi(this);// 创建场景scene = new QGraphicsScene(this);ui->graphicsView->setScene(scene);// 创建外框outerCircle = new QGraphicsEllipseItem(QRectF(-120,-120,240,240));outerCircle->setPen(QPen(Qt::black, 4));scene->addItem(outerCircle);// 创建中心点centerCircle = new QGraphicsEllipseItem(QRectF(-15,-15,30,30));centerCircle->setBrush(QBrush(Qt::red));centerCircle->setPen(QPen(Qt::black, 2));centerCircle->setZValue(1);scene->addItem(centerCircle);// 创建指针QPolygonF polygon;polygon << QPointF(-10, 0) << QPointF(0, -120) << QPointF(10, 0);pointer = new QGraphicsPolygonItem(polygon);pointer->setBrush(QBrush(Qt::red));pointer->setPen(QPen(Qt::black, 2));pointer->setZValue(2);pointer->setPos(0, 0);pointer->setRotation(0);scene->addItem(pointer);// 创建刻度线for (int i = 0; i < 12; i++) {QGraphicsLineItem *line = new QGraphicsLineItem(-100, 0, -80, 0);line->setPen(QPen(Qt::black, 3));line->setRotation(i * 30);line->setPos(0, 0);lines.append(line);scene->addItem(line);}// 启动定时器startTimer(100);
}MainWindow::~MainWindow()
{delete ui;
}void MainWindow::timerEvent(QTimerEvent *event)
{Q_UNUSED(event);int angle = ui->spinBox->value();QGraphicsItem *item = ui->graphicsView->scene()->items().at(3);pointer->setRotation(angle);
}

用Qt画一个漂亮预警仪表，具有立体感，代码，描述设计步骤

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