有些图形或者精美设计的可以用painter画刷实现。
案例汽车仪表盘：实现代码：#include "mainwindow.h"
#include "ui_mainwindow.h"
MainWindow::MainWindow(QWidget *parent)
: QMainWindow(parent)
, ui(new Ui::MainWindow)
{
ui->setupUi(this);
setFixedSize(1280,800);
//设置背景墙
this->setStyleSheet("#MainWindow{background-image:url(:/res/pic/background.png)}");
//定时器动态增加时速
myTimer = new QTimer(this);
connect(myTimer,SIGNAL(timeout()),this,SLOT(slot_speed_changed()));
}
void MainWindow::paintEvent(QPaintEvent*)
{
QPainter painter(this);
int width=this->width();
int height=this->height() - 100;//移动仪表盘的高度
int radius=((width>height)?height:width)/2.0;//仪表盘的中心位置
//移动画笔到中下方
painter.translate(width/2,height*0.6);
//启用反锯齿
painter.setRenderHint(QPainter::Antialiasing, true);
painter.setPen(Qt::NoPen);
//设置画刷颜色
painter.setBrush(QColor(138,43,226));
DrawSmallScale(painter,radius-60);//刻度线
DrawDigital(painter,radius-90);//刻度数字
/*所有形状绘画*/
// DrawCircle_bom(painter,radius-40); //扇形大圆
DrawCircle(painter,radius-35); //渐变发光外扇形
DrawCircle_arc(painter,radius - 40);//动态扇形环
DrawPointer(painter,radius-130);//指针
DrawCircle_line(painter,radius-35); //最外细圆线
DrawCircle_bom_big(painter,radius-150);//中间大圆
DrawCircle_bom_shine(painter,radius - 230);//渐变发光内圈
DrawCircle_bom_small(painter,radius - 200);//中间小圆
DrawUnit(painter,radius - 390);//单位
DrawNum(painter,radius-300);//时速
}
//绘制外圈点
void MainWindow::DrawPoint(QPainter& painter,int radius)
{
//组装点的路径图
QPainterPath pointPath;
pointPath.moveTo(-2,-2);
pointPath.lineTo(2,-2);
pointPath.lineTo(2,2);
pointPath.lineTo(0,4);
pointPath.lineTo(-2,2);
//绘制13个小点
for(int i=0;i<13;++i){
QPointF point(0,0);
painter.save();
painter.setBrush(QColor(250,252,78));
//计算并移动绘图对象中心点
point.setX(radius*qCos(((210-i*20)*M_PI)/180));
point.setY(radius*qSin(((210-i*20)*M_PI)/180));
//计算并移动绘图对象的中心点
painter.translate(point.x(),-point.y());
//计算并选择绘图对象坐标
painter.rotate(-120+i*20);
//绘制路径
painter.drawPath(pointPath);
painter.restore();
}
}
void MainWindow::DrawDigital(QPainter& painter,int radius)
{
//设置画笔，画笔默认NOPEN
painter.setPen(QColor(255,255,255));
QFont font;
font.setFamily("Arial");
font.setPointSize(15);
font.setBold(true);
painter.setFont(font);
for(int i=0;i<13;++i){
QPointF point(0,0);
painter.save();
point.setX(radius*qCos(((210-i*20)*M_PI)/180));
point.setY(radius*qSin(((210-i*20)*M_PI)/180));
painter.translate(point.x(),-point.y());
painter.rotate(-120+i*20);
painter.drawText(-25, 0, 50, 20,Qt::AlignCenter,QString::number(i*20));
painter.restore();
}
//还原画笔
painter.setPen(Qt::NoPen);
}
void MainWindow::DrawCircle_bom(QPainter& painter,int radius)
{
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath outRing;
outRing.moveTo(0,0);
outRing.arcTo(-radius,-radius, 2*radius,2*radius,-30,240);
outRing.closeSubpath();
//设置画刷
painter.setBrush(QColor(14,15,33));
painter.drawPath(outRing);
painter.restore();
}
void MainWindow::DrawCircle_bom_shine(QPainter& painter,int radius)
{
painter.save();
QRadialGradient radialGradient(0,0,radius,0,0);
// radialGradient.setColorAt(0.5,QColor(8,77,197));
radialGradient.setColorAt(0.5,QColor(10,68,185,150));
radialGradient.setColorAt(1.0,Qt::transparent);
painter.setBrush(QBrush(radialGradient));
painter.drawRect(-radius,-radius,2*(radius),2*(radius));
painter.restore();
}
void MainWindow::DrawCircle_bom_big(QPainter& painter,int radius)
{
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath inRing;
inRing.moveTo(0,0);
inRing.addEllipse(-radius+50,-radius + 50,2*(radius-50),2*(radius-50));
//设置画刷
painter.setBrush(QColor(10,20,30));
painter.drawPath(inRing);
painter.restore();
}
void MainWindow::DrawCircle_bom_small(QPainter& painter,int radius)
{
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath inRing;
inRing.moveTo(0,0);
inRing.addEllipse(-radius+50,-radius + 50,2*(radius-50),2*(radius-50));
//设置画刷
painter.setBrush(QColor(10,20,30));
painter.drawPath(inRing);
painter.restore();
}
void MainWindow::DrawCircle_arc(QPainter& painter,int radius)
{
QRect rect(-radius,-radius,2*radius,2*radius);
QConicalGradient Conical(0,0,-70);
Conical.setColorAt(0.1,QColor(255,88,127,200));//红色
Conical.setColorAt(0.5,QColor(53,179,251,150));//蓝色
painter.setBrush(Conical);
painter.drawPie(rect,210*16,-(degRotate)*16);
}
void MainWindow::DrawCircle(QPainter& painter,int radius)
{
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath outRing;
QPainterPath inRing;
outRing.moveTo(0,0);
inRing.moveTo(0,0);
outRing.arcTo(-radius,-radius, 2*radius,2*radius,-30,240);
inRing.addEllipse(-radius+50,-radius + 50,2*(radius-50),2*(radius-50));
outRing.closeSubpath();
//设置渐变色k
QRadialGradient radialGradient(0,0,radius,0,0);
radialGradient.setColorAt(1,QColor(0,82,199));
radialGradient.setColorAt(0.92,Qt::transparent);
//设置画刷
painter.setBrush(radialGradient);
//大圆减小圆
painter.drawPath(outRing.subtracted(inRing));
painter.restore();
}
void MainWindow::DrawCircle_line(QPainter& painter,int radius)
{
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath outRing;
QPainterPath inRing;
outRing.moveTo(0,0);
inRing.moveTo(0,0);
outRing.arcTo(-radius,-radius, 2*radius,2*radius,-30,240);
inRing.addEllipse(-radius+2,-radius+2,2*(radius-2),2*(radius-2));
outRing.closeSubpath();
//设置画刷
painter.setBrush(QColor(5,228,255));
//大圆减小圆
painter.drawPath(outRing.subtracted(inRing));
painter.restore();
}
//绘制刻度
void MainWindow::DrawSmallScale(QPainter& painter,int radius)
{
//组装点的路径图
QPainterPath pointPath_small;
pointPath_small.moveTo(-2,-2);
pointPath_small.lineTo(2,-2);
pointPath_small.lineTo(2,8);
pointPath_small.lineTo(-2,8);
QPainterPath pointPath_big;
pointPath_big.moveTo(-2,-2);
pointPath_big.lineTo(2,-2);
pointPath_big.lineTo(2,20);
pointPath_big.lineTo(-2,20);
//绘制121个小点
for(int i=0;i<121;i+=2){
QPointF point(0,0);
painter.save();
point.setX(radius*qCos(((210-i*2)*M_PI)/180));
point.setY(radius*qSin(((210-i*2)*M_PI)/180));
painter.translate(point.x(),-point.y());
painter.rotate(-120+i*2);
if(i<80)
{
painter.setBrush(QColor(255,255,255));
}
if(i>=80)
{
painter.setBrush(QColor(235,70,70));
}
if(i%5 == 0)
{
painter.drawPath(pointPath_big);//绘画大刻度
}else
{
painter.drawPath(pointPath_small);//绘画小刻度
}
painter.restore();
}
}
//绘制文字
void MainWindow::DrawUnit(QPainter& painter,int radius)
{
painter.save();
painter.setPen(QColor(255,255,255));
QFont font;
font.setFamily("Arial");
font.setPointSize(16);
font.setBold(true);
painter.setFont(font);
painter.drawText(-50, -radius, 100, 20,Qt::AlignCenter,QString("km/h"));
painter.drawText(-60, -radius + 130, 120, 40,Qt::AlignCenter,QString(u8"当前车速"));
painter.setPen(QColor(255,255,255,50));
painter.drawText(-120, -radius + 280, 250, 40,Qt::AlignCenter,QString(u8"-请按space键加速-"));
painter.restore();
}
//绘制实时时速数字
void MainWindow::DrawNum(QPainter& painter,int radius)
{
painter.save();
painter.setPen(QColor(255,255,255));
QFont font;
font.setFamily("Arial");
font.setPointSize(45);
painter.setFont(font);
painter.drawText(-75, -radius - 20, 150, 100,Qt::AlignCenter,QString::number(degRotate));
painter.restore();
}
//绘制指针
void MainWindow::DrawPointer(QPainter& painter,int radius)
{
//组装点的路径图
QPainterPath pointPath;
pointPath.moveTo(10,0);
pointPath.lineTo(1,-radius);
pointPath.lineTo(-1,-radius);
pointPath.lineTo(-10,0);
pointPath.arcTo(-10,0,20,20,180,180);
QPainterPath inRing;
inRing.addEllipse(-5,-5,10,10);
painter.save();
//计算并选择绘图对象坐标
painter.rotate(degRotate - 120);
painter.setBrush(QColor(255,255,255));
painter.drawPath(pointPath.subtracted(inRing));
painter.restore();
}
//动态增加时速画面效果
void MainWindow::slot_speed_changed()
{
if(direction == 1)//加速
{
degRotate++;
if(degRotate > 240)
degRotate = 240;
}
else if(direction == 0)//减速
{
degRotate--;
if(degRotate < 0)
{
degRotate = 0;
myTimer->stop();
}
}
update();//刷新画面。很重要！
}
void MainWindow::keyPressEvent(QKeyEvent *event)
{
if(event->key() == Qt::Key_Space)
{
if(direction == 0)
{
myTimer->start(1);
direction = 1;
}
}
}
//按键释放事件
void MainWindow::keyReleaseEvent(QKeyEvent *event)
{
if(event->key() == Qt::Key_Space)
{
direction = 0;
}
}
MainWindow::~MainWindow()
{
delete ui;
}代码分析：QPainter QPainter的核心功能是绘图，但该类也提供了几个函数，允许用户自定义QPainter的设置及其渲染质量，以及其他支持剪切的功能。此外，还可以通过指定画家的构图模式来控制不同的形状如何合并在一起。QPainter只能在paintEvent()函数中或被paintEvent()调用的函数中使用。
上面代码常用的一些设置：
//移动画笔到中下方
painter.translate(width/2,height*0.6);
//启用反锯齿
painter.setRenderHint(QPainter::Antialiasing, true);
painter.setPen(Qt::NoPen);
//设置画刷颜色
painter.setBrush(QColor(138,43,226));常用的函数：
drawEllipsevoid QPainter::drawEllipse(const QRectF &rectangle)上面主要是画椭圆，但前提是要给定长方形，在其中画椭圆
addEllipsevoid QPainterPath::addEllipse(qreal x, qreal y, qreal w, qreal h)上面函数是椭圆或圆或圆弧，当x,y两个点为正方形，画的为圆
//-radius+50,-radius + 50 是以此为坐标点，创建一个高为2*(radius-50)，宽为2*(radius-50)的内切圆
inRing.addEllipse(-radius+50,-radius + 50,2*(radius-50),2*(radius-50));
//arcTo
void QPainterPath::arcTo(qreal x, qreal y, qreal w, qreal h, qreal startAngle, qreal arcLength)跟addEllipse一样也是创建内切圆，但是它定义了起始位置
//定义 内切圆后去-30到240度的圆弧，逆时针绘制所以是-30度到240度
outRing.arcTo(-radius,-radius, 2*radius,2*radius,-30,240);
内切圆的用法：
//保存绘图对象
painter.save();
//计算大小圆路径
QPainterPath outRing;
QPainterPath inRing;
outRing.moveTo(0,0);
inRing.moveTo(0,0);
outRing.arcTo(-radius,-radius, 2*radius,2*radius,-30,240);
inRing.addEllipse(-radius+50,-radius+50,2*(radius-50),2*(radius-50));
outRing.closeSubpath();
//设置渐变色k
QRadialGradient radialGradient(0,0,radius,0,0);
radialGradient.setColorAt(1,QColor(0,82,199));
radialGradient.setColorAt(0.92,Qt::transparent);
//设置画刷
painter.setBrush(radialGradient);
//大圆减小圆
painter.drawPath(outRing.subtracted(inRing));
painter.restore();translate变更坐标原点
inline void QPainter::translate(qreal dx, qreal dy)//将坐标原点变更为 point.x(),-point.y()
QPointF point(0,0);
painter.save();
//应用三角函数知识确定x,y坐标的位置
point.setX(radius*qCos(((210-i*2)*M_PI)/180));
point.setY(radius*qSin(((210-i*2)*M_PI)/180));
painter.translate(point.x(),-point.y());rotate
顺时针旋转一个角度
//因为画是个圆弧，两边各多了30度，可以将此行注释点观察，不旋转的样子，来进行推断
painter.rotate(-120+i*2);