Qt5-雷达项目

 界面:

widget.h 

#ifndef WIDGET_H
#define WIDGET_H

#include <QTimer>
#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui { class Widget; }
QT_END_NAMESPACE

class Widget : public QWidget
{
    Q_OBJECT

public:
    Widget(QWidget *parent = nullptr);
    ~Widget();
protected:
    void paintEvent(QPaintEvent *event) override;
private:
    Ui::Widget *ui;
    QTimer *timer;
    int startAngle=0;
};
#endif // WIDGET_H

widget.c 

#include "widget.h"
#include "ui_widget.h"

#include <QPainter>
#include <QTimer>

Widget::Widget(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::Widget)
{
    ui->setupUi(this);
    
    timer = new QTimer(this);
    connect(timer, &QTimer::timeout,[=](){
        //不断变化扇形的启动位置
        startAngle += 4;
        if(startAngle >= 360){
            startAngle = 0;
        }
        update();
    });
    timer->start(30);
    
}

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

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter paint(this);//实列化一个画家
    paint.setRenderHint(QPainter::Antialiasing,true);//时画出来的看起来更顺滑
    QBrush brush(Qt::gray);//实列化一个画刷
    paint.setBrush(brush);//将画刷交给画家paint
    
    //应为现在画家拿的是黑色画刷所有画出来黑色的矩形,rect为窗口这个矩形
    paint.drawRect(rect());
    paint.setBrush(Qt::NoBrush);//将画家的画刷丢掉
    QPen pen(Qt::green,3);//实力画一个粗细程度为3的绿色画笔
    paint.translate(rect().center());//设置0点
    paint.setPen(pen);//将画笔交给画家,现在画家拿的是画笔
    
    /*画圆*/
    paint.drawEllipse(QPoint(0,0),1,1);//在(0,0)画一个100圆
    paint.drawEllipse(QPoint(0,0),50,50);//在(0,0)画一个100圆
    paint.drawEllipse(QPoint(0,0),100,100);//在(0,0)画一个100圆
    paint.drawEllipse(QPoint(0,0),150,150);//在(0,0)画一个100圆
    paint.drawEllipse(QPoint(0,0),200,200);//在(0,0)画一个100圆
    paint.drawEllipse(QPoint(0,0),250,250);//在(0,0)画一个100圆
    
    
    /*画横线*/
    paint.drawLine(0,-250,0,250);
    paint.drawLine(-250,0,250,0);
    
    /*锥形渐变*/
    QConicalGradient conicalGradient(0, 0, -startAngle);
    conicalGradient.setColorAt(0,QColor(0,255,0,200));
    conicalGradient.setColorAt(0.1,QColor(0,255,0,100));
    conicalGradient.setColorAt(0.2,QColor(0,255,0,0));
    conicalGradient.setColorAt(1,QColor(0,255,0,0));
    paint.setBrush(conicalGradient);
    paint.setPen(Qt::NoPen);
    
    /*画扇形*/
    QRect Rect_Pie(-250,-250,500,500);
    paint.drawPie(Rect_Pie,-startAngle*16,120*16);
    
    
}