Qt：玩转QPainter后转之时钟(步骤详细、包含源码)

血不热了2024-09-03 13:28

前言

简单了解了QPainter之后当然是要找两个例子练练手啦。

正文

先看效果图

在绘制之前我们要先构思好自己要绘制的对象可以分成几部分，比如我要绘制时钟的话，我可以分成：外边框(圆环或者圆)，圆形背景，刻度，时间数字，秒针，分针，时针，中心点；
当然也可以不分这么细，或者分的更细，留下接口以实现更多的效果。

绘制外边框

cpp 复制代码 
ClockPainter::ClockPainter(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::ClockPainter)
{
    ui->setupUi(this);
    // 外半径
    outRadius = 108;
    // 内半径
    inRadius = 100;
    crownColorStart = QColor(255,0,0);
    crownColorEnd = QColor(64,156,250);
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
}

void ClockPainter::drawCrown(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 渐变
    QLinearGradient gradient(-outRadius, -outRadius, outRadius, outRadius);
    gradient.setColorAt(0, crownColorStart);
    gradient.setColorAt(1, crownColorEnd);
    painter->setBrush(gradient);
    painter->drawEllipse(-outRadius, -outRadius, outRadius<<1, outRadius<<1);
    painter->restore();
}
效果

绘制背景

cpp 复制代码 
ClockPainter::ClockPainter(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::ClockPainter)
{
    ui->setupUi(this);
    // 外半径
    outRadius = 108;
    // 内半径
    inRadius = 100;
    crownColorStart = QColor(255,0,0);
    crownColorEnd = QColor(64,156,250);
}


void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
}

void ClockPainter::drawBg(QPainter *painter)
{
    painter->save();
    painter->setBrush(Qt::black);
    painter->drawEllipse(-inRadius, -inRadius, inRadius<<1, inRadius<<1);
    painter->restore();
}
效果

绘制刻度

cpp 复制代码 
void ClockPainter::drawScale(QPainter *painter)
{
    painter->save();
    QPen pen;
    pen.setColor(Qt::white);

    for (int i = 0; i < 60; ++i) {
        // 长的和短的粗细不一样
        if (i % 5 == 0) {
            pen.setWidth(2);
            pen.setCapStyle(Qt::RoundCap);
            painter->setPen(pen);
            painter->drawLine(inRadius - 8, 0, inRadius, 0);
        } else {
            pen.setWidth(1);
            painter->setPen(pen);
            painter->drawLine(inRadius - 4, 0, inRadius, 0);
        }
        painter->rotate(6);
    }
    painter->restore();
}


void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
}
效果

绘制时间数字

cpp 复制代码 
QRectF ClockPainter::textRectF(qreal radius, int pointSize, qreal angle)
{
    // 用于计算每个数字所在的矩形
    QRectF rectF;
    rectF.setX(radius*qCos(angle*M_PI/180.0) - pointSize*2);
    rectF.setY(radius*qSin(angle*M_PI/180.0) - pointSize/2.0);
    rectF.setWidth(pointSize*4);
    rectF.setHeight(pointSize*1.5);
    return rectF;
}

void ClockPainter::drawScaleNum(QPainter *painter)
{
    painter->save();
    // 获取当前字体
    QFont font = painter->font();
    // 设置粗体
    font.setBold(true);
    painter->setFont(font);
    int pointSize = font.pointSize();
    painter->setPen(Qt::white);
    int nHour = 0;
    for (int i = 0; i < 12; ++i) {
      nHour = i + 3;
      if (nHour > 12)
        nHour -= 12;
      painter->drawText(textRectF(inRadius*0.8, pointSize, i * 30), Qt::AlignCenter, QString::number(nHour));
    }
    painter->restore();
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
}
效果

绘制中心点

cpp 复制代码 
void ClockPainter::drawCenterDot(QPainter *painter)
{
    painter->save();
    painter->setPen(Qt::NoPen);
    QLinearGradient gradient(-10, -10, 10, 10);
    gradient.setColorAt(0, Qt::gray);
    gradient.setColorAt(0.2,Qt::black);
    gradient.setColorAt(1, Qt::gray);

    painter->setBrush(gradient);
    painter->drawEllipse(-5,-5,10,10);
    painter->restore();
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
    drawCenterDot(&painter);

}
效果

绘制秒针

cpp 复制代码 
void ClockPainter::drawSec(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-3,-2)<<QPoint(70,-1)<<QPoint(70,1)<<QPoint(-3,2);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
    drawSec(&painter);
    drawCenterDot(&painter);

}
效果

绘制分针

cpp 复制代码 
void ClockPainter::drawMin(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-6,-3)<<QPoint(63,-2)<<QPoint(63,2)<<QPoint(-6,3);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
    drawMin(&painter);
    drawSec(&painter);
    drawCenterDot(&painter);

}
效果

绘制时针

cpp 复制代码 
void ClockPainter::drawHour(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-6,-4)<<QPoint(50,-3)<<QPoint(50,3)<<QPoint(-6,4);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
    drawHour(&painter);
    drawMin(&painter);
    drawSec(&painter);
    drawCenterDot(&painter);

}
效果

其实从话指针就很容易看出来，只要会画一个，其余的就改动一点，代码重复性极高

添加定时器使得指针动起来

cpp 复制代码 
ClockPainter::ClockPainter(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::ClockPainter)
{
    ui->setupUi(this);
    // 外半径
    outRadius = 108;
    // 内半径
    inRadius = 100;
    crownColorStart = QColor(255,0,0);
    crownColorEnd = QColor(64,156,250);
    // 初始化时间
    QTime time = QTime::currentTime();
    hour = time.hour();
    min = time.minute();
    sec = time.second();
    // 初始化定时器
    timer = new QTimer(this);
    connect(timer, &QTimer::timeout, this, &ClockPainter::updateTime);
    // 设置时间间隔为1s
    timer->start(1000);

}
void ClockPainter::updateTime()
{
    QTime time = QTime::currentTime();
    hour = time.hour();
    // 12小时制
    if (hour > 12) {
        hour -= 12;
    }
    min = time.minute();
    sec = time.second();
    // 更新图像
    update();
}
//关键是要在相应的绘制指针的函数中调用rotate函数，使得绘制的图像旋转
效果

总体代码

这里我定义了指针的颜色，但是我并没有使用，是想留一个接口进行下一步开发。

头文件

cpp 复制代码 
#ifndef CLOCKPAINTER_H
#define CLOCKPAINTER_H

#include <QWidget>

QT_BEGIN_NAMESPACE
namespace Ui { class ClockPainter; }
QT_END_NAMESPACE

class ClockPainter : public QWidget
{
    Q_OBJECT

public:
    ClockPainter(QWidget *parent = nullptr);
    ~ClockPainter();


protected:
    void paintEvent(QPaintEvent *);
    // 画外边框
    void drawCrown(QPainter *painter);
    // 画背景
    void drawBg(QPainter *painter);
    // 画刻度
    void drawScale(QPainter *painter);
    // 画刻度上的数字
    void drawScaleNum(QPainter *painter);
    // 时针
    void drawHour(QPainter *painter);
    // 分针
    void drawMin(QPainter *painter);
    // 秒针
    void drawSec(QPainter *painter);
    // 画中心点
    void drawCenterDot(QPainter *painter);
    // 处理数字位置
    QRectF textRectF(qreal radius, int pointSize, qreal angle);


private slots:
    void updateTime();
private:
    Ui::ClockPainter* ui;
    // 外边框半径
    int outRadius;
    // 内边框半径
    int inRadius;
    // 外边框渐变开始颜色
    QColor crownColorStart;
    // 外边框渐变结束颜色
    QColor crownColorEnd;
    // 背景色
    QColor background;
    // 时钟指针颜色
    QColor pointerHourColor;
    // 分钟指针颜色
    QColor pointerMinColor;
    // 秒钟指针颜色
    QColor pointerSecColor;
    // 定时器绘制
    QTimer *timer;
    // 时分秒
    int hour, min, sec;
};

#endif // CLOCKPAINTER_H

源文件

cpp 复制代码 
#include "clockpainter.h"
#include "ui_clockpainter.h"
#include "qpainter.h"
#include "qpen.h"
#include "qcolor.h"
#include "qpolygon.h"
#include "qfont.h"
#include "qtimer.h"
#include "qmath.h"
#include "qrect.h"
#include "qtransform.h"
#include <QTime>
#include <QLinearGradient>
#include "qdebug.h"

ClockPainter::ClockPainter(QWidget *parent)
    : QWidget(parent)
    , ui(new Ui::ClockPainter)
{
    ui->setupUi(this);
    // 外半径
    outRadius = 108;
    // 内半径
    inRadius = 100;
    crownColorStart = QColor(255,0,0);
    crownColorEnd = QColor(64,156,250);
    // 初始化时间
    QTime time = QTime::currentTime();
    hour = time.hour();
    min = time.minute();
    sec = time.second();
    // 初始化定时器
    timer = new QTimer(this);
    connect(timer, &QTimer::timeout, this, &ClockPainter::updateTime);
    // 设置时间间隔为1s
    timer->start(1000);

}

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

void ClockPainter::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    // 设置图形和文本抗锯齿
    painter.setRenderHints(QPainter::Antialiasing | QPainter::TextAntialiasing);
    // 将绘制点移动到窗口中心
    painter.translate(width() / 2, height() / 2);
    drawCrown(&painter);
    drawBg(&painter);
    drawScale(&painter);
    drawScaleNum(&painter);
    drawHour(&painter);
    drawMin(&painter);
    drawSec(&painter);
    drawCenterDot(&painter);

}

void ClockPainter::drawCrown(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 渐变
    QLinearGradient gradient(-outRadius, -outRadius, outRadius, outRadius);
    gradient.setColorAt(0, crownColorStart);
    gradient.setColorAt(1, crownColorEnd);
    painter->setBrush(gradient);
    painter->drawEllipse(-outRadius, -outRadius, outRadius<<1, outRadius<<1);
    painter->restore();
}

void ClockPainter::drawBg(QPainter *painter)
{
    painter->save();
    painter->setBrush(Qt::black);
    painter->drawEllipse(-inRadius, -inRadius, inRadius<<1, inRadius<<1);
    painter->restore();
}

void ClockPainter::drawScale(QPainter *painter)
{
    painter->save();
    QPen pen;
    pen.setColor(Qt::white);

    for (int i = 0; i < 60; ++i) {
        // 长的和短的粗细不一样
        if (i % 5 == 0) {
            pen.setWidth(2);
            pen.setCapStyle(Qt::RoundCap);
            painter->setPen(pen);
            painter->drawLine(inRadius - 8, 0, inRadius, 0);
        } else {
            pen.setWidth(1);
            painter->setPen(pen);
            painter->drawLine(inRadius - 4, 0, inRadius, 0);
        }
        painter->rotate(6);
    }
    painter->restore();
}

void ClockPainter::drawScaleNum(QPainter *painter)
{
    painter->save();
    // 获取当前字体
    QFont font = painter->font();
    // 设置粗体
    font.setBold(true);
    painter->setFont(font);
    int pointSize = font.pointSize();
    painter->setPen(Qt::white);
    int nHour = 0;
    for (int i = 0; i < 12; ++i) {
      nHour = i + 3;
      if (nHour > 12)
        nHour -= 12;
      painter->drawText(textRectF(inRadius*0.8, pointSize, i * 30), Qt::AlignCenter, QString::number(nHour));
    }
    painter->restore();
}

void ClockPainter::drawHour(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-6,-4)<<QPoint(50,-3)<<QPoint(50,3)<<QPoint(-6,4);
    // 旋转,角度需要减去90，因为不减的话，是从12开始计算角度
    painter->rotate(30.0 * ((hour + min / 60.0)) - 90);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::drawMin(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-6,-3)<<QPoint(63,-2)<<QPoint(63,2)<<QPoint(-6,3);
    // 旋转,角度需要减去90，因为不减的话，是从12开始计算角度
    painter->rotate(6.0 * (min + sec / 60.0) - 90);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::drawSec(QPainter *painter)
{
    painter->save();
    // 接下来的绘制不用笔，如果没有填充的话将什么效果都没有
    painter->setPen(Qt::NoPen);
    // 画一个四边形，两头大，两头小
    painter->setBrush(Qt::gray);
    QPolygon polygon;
    polygon<<QPoint(-3,-2)<<QPoint(70,-1)<<QPoint(70,1)<<QPoint(-3,2);
    // 旋转,角度需要减去90，因为不减的话，是从12开始计算角度
    painter->rotate(6.0 * sec - 90);
    painter->drawPolygon(polygon);
    painter->restore();
}

void ClockPainter::drawCenterDot(QPainter *painter)
{
    painter->save();
    painter->setPen(Qt::NoPen);
    QLinearGradient gradient(-10, -10, 10, 10);
    gradient.setColorAt(0, Qt::gray);
    gradient.setColorAt(0.2,Qt::black);
    gradient.setColorAt(1, Qt::gray);

    painter->setBrush(gradient);
    painter->drawEllipse(-5,-5,10,10);
    painter->restore();
}

QRectF ClockPainter::textRectF(qreal radius, int pointSize, qreal angle)
{
    // 用于计算每个数字所在的矩形
    QRectF rectF;
    rectF.setX(radius*qCos(angle*M_PI/180.0) - pointSize*2);
    rectF.setY(radius*qSin(angle*M_PI/180.0) - pointSize/2.0);
    rectF.setWidth(pointSize*4);
    rectF.setHeight(pointSize*1.5);
    return rectF;
}

void ClockPainter::updateTime()
{
    QTime time = QTime::currentTime();
    hour = time.hour();
    // 12小时制
    if (hour > 12) {
        hour -= 12;
    }
    min = time.minute();
    sec = time.second();
    // 更新图像
    update();
}
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