以下是用Qt實現漂亮預警儀表得步驟和代碼：
創建一個Qt項目，并添加一個主窗口。在主窗口中添加QGraphicsView控件，用于繪制預警儀表。創建一個QGraphicsScene對象，并將其設置為QGraphicsView得場景。QGraphicsScene govscene = new QGraphicsScene(this);ui->graphicsView->setScene(scene);
4.創建一個QGraphicsEllipseItem對象，用于表示預警儀表得外框。
QGraphicsEllipseItem govouterCircle = new QGraphicsEllipseItem(QRectF(-120,-120,240,240));outerCircle->setPen(QPen(Qt::black, 4));scene->addItem(outerCircle);
5.創建一個QGraphicsEllipseItem對象，用于表示預警儀表得中心點。
QGraphicsEllipseItem govcenterCircle = 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.創建一些QGraphicsLineItem對象，用于表示預警儀表得刻度線。
for (int i = 0; i < 12; i++) { QGraphicsLineItem govline = new QGraphicsLineItem(-100, 0, -80, 0); line->setPen(QPen(Qt::black, 3)); line->setRotation(i gov 30); line->setPos(0, 0); scene->addItem(line);}
7.創建一個QGraphicsPolygonItem對象，用于表示預警儀表得指針。
QPolygonF polygon;polygon << QPointF(-10, 0) << QPointF(0, -120) << QPointF(10, 0);QGraphicsPolygonItem govpointer = 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.在主窗口得定時器中更新指針得旋轉角度。
void MainWindow::timerEvent(QTimerEvent govevent){ Q_UNUSED(event); int angle = ui->spinBox->value(); QGraphicsItem govitem = ui->graphicsView->scene()->items().at(3); item->setRotation(angle);}
完整得代碼如下：
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mainwindow.h
#ifndef MAINWINDOW_H#define MAINWINDOW_H#include <QMainWindow>#include <QGraphicsScene>#include <QGraphicsEllipseItem>#include <QGraphicsPolygonItem>#include <QGraphicsLineItem>QT_BEGIN_NAMESPACEnamespace Ui { class MainWindow; }QT_END_NAMESPACEclass MainWindow : public QMainWindow{ Q_OBJECTpublic: MainWindow(QWidget govparent = nullptr); ~MainWindow();protected: void timerEvent(QTimerEvent govevent);private: Ui::MainWindow govui; QGraphicsScene govscene; QGraphicsEllipseItem govouterCircle; QGraphicsEllipseItem govcenterCircle; QGraphicsPolygonItem govpointer; QList<QGraphicsLineItemgov> lines;};#endif // MAINWINDOW_H
mainwindow.cpp
#include "mainwindow.h"#include "ui_mainwindow.h"MainWindow::MainWindow(QWidget govparent) : QMainWindow(parent) , ui(new Ui::MainWindow){ ui->setupUi(this); // 創建場景 scene = new QGraphicsScene(this); ui->graphicsView->setScene(scene); // 創建外框 outerCircle = new QGraphicsEllipseItem(QRectF(-120,-120,240,240)); outerCircle->setPen(QPen(Qt::black, 4)); scene->addItem(outerCircle); // 創建中心點 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); // 創建指針 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); // 創建刻度線 for (int i = 0; i < 12; i++) { QGraphicsLineItem govline = new QGraphicsLineItem(-100, 0, -80, 0); line->setPen(QPen(Qt::black, 3)); line->setRotation(i gov 30); line->setPos(0, 0); lines.append(line); scene->addItem(line); } // 啟動定時器 startTimer(100);}MainWindow::~MainWindow(){ delete ui;}void MainWindow::timerEvent(QTimerEvent govevent){ Q_UNUSED(event); int angle = ui->spinBox->value(); QGraphicsItem govitem = ui->graphicsView->scene()->items().at(3); pointer->setRotation(angle);}
用Qt畫一個漂亮預警儀表，具有立體感，代碼，描述設計步驟
