基于QT绘制一个漂亮的预警仪表

2023-05-14 17:14

短信预约 -IT技能 免费直播动态提醒

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 <QMainWindow>
#include <QGraphicsScene>
#include <QGraphicsEllipseItem>
#include <QGraphicsPolygonItem>
#include <QGraphicsLineItem>
 
QT_BEGIN_NAMESPACE
namespace Ui { class MainWindow; }
QT_END_NAMESPACE
 
class MainWindow : public QMainWindow
{
    Q_OBJECT
 
public:
    MainWindow(QWidget *parent = nullptr);
    ~MainWindow();
 
protected:
    void timerEvent(QTimerEvent *event);
 
private:
    Ui::MainWindow *ui;
    QGraphicsScene *scene;
    QGraphicsEllipseItem *outerCircle;
    QGraphicsEllipseItem *centerCircle;
    QGraphicsPolygonItem *pointer;
    QList<QGraphicsLineItem*> 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