Qt总结之六：QPaintEvent绘制雷达图

前言

关于雷达样式可参考文章：https://blog.csdn.net/Aidam_Bo/article/details/84260883

一、代码

头文件.h

#ifndef RADARSCAN_H
#define RADARSCAN_H

#include <QtWidgets/QWidget>
#include "ui_radarscan.h"

class RadarScan : public QWidget
{
	Q_OBJECT

public:
	RadarScan(QWidget *parent = 0);
	~RadarScan();

	QPixmap paintWidget();

protected:
	void paintEvent(QPaintEvent *event);
	void resizeEvent(QResizeEvent *event);
	protected slots:
	void timerTimeOut();

private:
	QTimer *timer;
	QPoint point;
	int i_diameter = 0;
	double d_angle = 0;
	QList<QPixmap> list_pixmap;

private:
	Ui::RadarScanClass ui;
};

#endif // RADARSCAN_H

实现.cpp

#include "radarscan.h"
#include <QPainter>
#include <QPen>
#include <QDebug>
#include <QLinearGradient>
#include <QTimer>
#include <QTime>

RadarScan::RadarScan(QWidget *parent)
	: QWidget(parent)
{
	ui.setupUi(this);

	this->setStyleSheet("background-color:black");//设置窗口背景色为黑色
	timer = new QTimer();
	connect(timer, SIGNAL(timeout()), this, SLOT(timerTimeOut()));

	timer->start(10);
}

RadarScan::~RadarScan()
{

}
void RadarScan::resizeEvent(QResizeEvent *event)
{
	if (this->width() > this->height()){
		point = QPoint((this->width() - this->height()) / 2 + (this->height() - 12) / 2, this->height() / 2);
		i_diameter = this->height() - 12;
	}
	else{
		point = QPoint(this->width() / 2, (this->height() - this->width()) / 2 + (this->width() - 12) / 2);
		i_diameter = this->width() - 12;
	}
}

void RadarScan::timerTimeOut()
{
	timer->start(10);
	d_angle += 3.14 / 720;
	if (d_angle >= 6.28){
		d_angle = 0;
	}
	update();

}

void RadarScan::paintEvent(QPaintEvent *event)
{
	QPainter p_painter(this);
	//反锯齿
	p_painter.setRenderHint(QPainter::Antialiasing);

	p_painter.drawPixmap(0, 0, this->width(), this->height(), paintWidget());

	QWidget::paintEvent(event);
}

QPixmap RadarScan::paintWidget()
{
	QPixmap pixmap(this->width(), this->height());
	QPainter p_painter(&pixmap);
	QPen pen;
	QTime timedebug;
	timedebug.start();
	//反锯齿
	p_painter.setRenderHint(QPainter::Antialiasing);
	pixmap.fill(Qt::black);

	pen.setColor(Qt::green);
	p_painter.setPen(pen);

	pen.setColor(Qt::gray);
	p_painter.setPen(pen);
	p_painter.drawLine(point.x(), point.y() - i_diameter / 2 - 10, point.x(), point.y() + i_diameter / 2 + 10);//画坐标
	p_painter.drawLine(point.x() - i_diameter / 2 - 10, point.y(), point.x() + i_diameter / 2 + 10, point.y());
	pen.setColor(Qt::green);
	p_painter.setPen(pen);
	for (int i = 0; i<6; i++){
		p_painter.drawEllipse(point.x() - i_diameter*0.2*i / 2, point.y() - i_diameter*0.2*i / 2, i_diameter*0.2*i, i_diameter*0.2*i);
	}

	QConicalGradient conical_gradient(point, (6.28 - d_angle) / 6.28 * 720);//定义圆心和渐变的角度
	conical_gradient.setColorAt(0, Qt::green);
	conical_gradient.setColorAt(0.2, QColor(255, 255, 255, 0));
	p_painter.setBrush(conical_gradient);
	p_painter.drawEllipse(point.x() - i_diameter / 2, point.y() - i_diameter / 2, i_diameter, i_diameter);

	qDebug() << "time_end=" << timedebug.elapsed() << "ms";

	return pixmap;

}

二、细节实现

（1）重写resizeEvent函数，当窗口缩放时，对绘图的大小也进行缩放：

void RadarScan::resizeEvent(QResizeEvent *event)
{
    if(this->width() > this->height()){
        point = QPoint((this->width()-this->height())/2+(this->height()-12)/2,this->height()/2);
        i_diameter = this->height()-12;
    }else{
        point = QPoint(this->width()/2,(this->height()-this->width())/2+(this->width()-12)/2);
        i_diameter = this->width()-12;
    }
}

（2）在绘图函数中主要使用了QPixmap的定义画布，QPEN定义画笔，QConicalGradient对图形进行渐变填充，drawEllipse进行画圆：

QPixmap Widget::paintWidget()
{
    QPixmap pixmap(this->width(),this->height());
    QPainter p_painter(&pixmap);
    QPen pen;
    QTime timedebug;
    timedebug.start();
    //反锯齿
    p_painter.setRenderHint(QPainter::Antialiasing);
    pixmap.fill(Qt::black);
 
    pen.setColor(Qt::green);
    p_painter.setPen(pen);
 
    pen.setColor(Qt::gray);
    p_painter.setPen(pen);
    p_painter.drawLine(point.x(),point.y()-i_diameter/2-10,point.x(),point.y()+i_diameter/2+10);//画坐标
    p_painter.drawLine(point.x()-i_diameter/2-10,point.y(),point.x()+i_diameter/2+10,point.y());
    pen.setColor(Qt::green);
    p_painter.setPen(pen);
    for(int i=0; i<6; i++){
        p_painter.drawEllipse(point.x()-i_diameter*0.2*i/2,point.y()-i_diameter*0.2*i/2,i_diameter*0.2*i,i_diameter*0.2*i);
    }
 
    QConicalGradient conical_gradient(point,(6.28-d_angle)/6.28*720);//定义圆心和渐变的角度
    conical_gradient.setColorAt(0,Qt::green);
    conical_gradient.setColorAt(0.2,QColor(255,255,255,0));
    p_painter.setBrush(conical_gradient);
    p_painter.drawEllipse(point.x()-i_diameter/2,point.y()-i_diameter/2,i_diameter,i_diameter);
 
 
    qDebug()<<"time_end="<<timedebug.elapsed()<<"ms";
 
    return pixmap;
 
}

（3）QTimer定义定时器连接槽函数，当定时溢出时对图像进行刷新，同时重新开启定时，定时单位是毫秒：

void Widget::timerTimeOut()
{
    timer->start(10);
    d_angle += 3.14/720;
    if(d_angle >= 6.28){
        d_angle = 0;
    }
    update();
 
}

（4）最后对paintEven进行重构：

void Widget::paintEvent(QPaintEvent *event)
{
    QPainter p_painter(this);
    //反锯齿
    p_painter.setRenderHint(QPainter::Antialiasing);
 
    p_painter.drawPixmap(0,0,this->width(),this->height(),paintWidget());
 
    QWidget::paintEvent(event);
}