1、概述
源码放在文章末尾

该项目实现了可交互的动画验证码控件，趣味性十足：

字符变换动画
噪音动画
可拖动交互

项目demo演示如下所示：

项目部分代码如下所示：

#ifndef CAPTCHAMOVABLELABEL_H
#define CAPTCHAMOVABLELABEL_H#include <QLabel>
#include <QTime>
#include <QPropertyAnimation>
#include <QDebug>
#include <QMouseEvent>
#include <QPainter>
#include <QPainterPath>
#include <QApplication>
#include <QGraphicsDropShadowEffect>
#include <cmath>
#include <QTimer>#define CAPTCHA_REFRESH_DURATION 300 // 刷新的动画时长
#define CAPTCHA_CHAR_ANGLE_MAX 20 // 最大旋转角：20°
#define CAPTCHA_SHADOW_BLUR_MAX 80 // 最大的阴影模糊半径class CaptchaMovableLabel : public QLabel
{Q_OBJECTQ_PROPERTY(int refreshProgress READ getRefreshProgress WRITE setRefreshProgress)Q_PROPERTY(int pressProgress READ getPressProgress WRITE setPressProgress)
public:CaptchaMovableLabel(QWidget* parent);void setAngle(int angle);void setColor(QColor color);void setText(QString ch);void startRefreshAnimation();void setMoveBorder(QRect rect);QString text();protected:void paintEvent(QPaintEvent *) override;void mousePressEvent(QMouseEvent *ev) override;void mouseMoveEvent(QMouseEvent *ev) override;void mouseReleaseEvent(QMouseEvent *ev) override;private:void startPressAnimation(int end);void setRefreshProgress(int g);int getRefreshProgress();inline bool isNoAni();void setPressProgress(int g);int getPressProgress();private slots:void slotMovePos();private:QPoint press_pos;bool dragging =  false;bool moved = false;QGraphicsDropShadowEffect effect;QString ch;QColor color;int angle = 0;int refreshProgress = 100;QString prevCh;QColor prevColor;int prevAngle = 0;QString prevChar;int pressProgress = 0;bool inited = false;QTimer movingTimer;int moveR, moveG, moveB;
};#endif // CAPTCHAMOVABLELABEL_H

#include "captchamovablelabel.h"CaptchaMovableLabel::CaptchaMovableLabel(QWidget *parent) : QLabel(parent)
{effect.setOffset(0, 0);
//    effect.setBlurRadius(8);setGraphicsEffect(&effect);movingTimer.setInterval(30);movingTimer.setSingleShot(false);connect(&movingTimer, SIGNAL(timeout()), this, SLOT(slotMovePos()));
}void CaptchaMovableLabel::setAngle(int angle)
{this->prevAngle = this->angle;this->angle = angle;
}void CaptchaMovableLabel::setColor(QColor color)
{this->prevColor = this->color;this->color = color;moveR = qrand() % 5;moveG = qrand() % 5;moveB = qrand() % 5;movingTimer.start();
}void CaptchaMovableLabel::setText(QString text)
{this->prevCh = this->ch;this->ch = text;// 计算合适的高度QFontMetrics fm(this->font());double w = fm.horizontalAdvance(text)+2;double h = fm.height();const double PI = 3.141592;int xieHalf = sqrt(w*w/4+h*h/4); // 斜边的一半double a = atan(w/h) + CAPTCHA_CHAR_ANGLE_MAX * PI / 180; // 最大的倾斜角度int w2 = xieHalf * sin(a) * 2;a = atan(w/h) - CAPTCHA_CHAR_ANGLE_MAX * PI / 180;int h2 = xieHalf * cos(a) * 2;resize(w2, h2);
}void CaptchaMovableLabel::startRefreshAnimation()
{if (!inited) // 第一次，直接显示，取消动画{inited = true;return ;}QPropertyAnimation* ani = new QPropertyAnimation(this, "refreshProgress");ani->setStartValue(0);ani->setEndValue(100);ani->setDuration(qrand() % (CAPTCHA_REFRESH_DURATION / 3) + CAPTCHA_REFRESH_DURATION / 3);ani->start();connect(ani, SIGNAL(finished()), ani, SLOT(deleteLater()));connect(ani, SIGNAL(finished()), &movingTimer, SLOT(start()));
}QString CaptchaMovableLabel::text()
{return ch;
}void CaptchaMovableLabel::paintEvent(QPaintEvent *)
{QPainter painter(this);painter.setFont(this->font());painter.setRenderHint(QPainter::SmoothPixmapTransform);int w2 = width()/2, h2 = height()/2;painter.translate(w2, h2); // 平移到中心，绕中心点旋转if (isNoAni()) // 不在动画中，直接绘制{painter.setPen(color);painter.rotate(angle);painter.drawText(QRect(-w2, -h2, width(), height()), Qt::AlignCenter, ch);return ;}// 动画里面，前后渐变替换double newProp = refreshProgress / 100.0;double oldProp = 1.0 - newProp;double a = prevAngle * oldProp + angle * newProp + 0.5;painter.save();painter.rotate(a);QColor c = prevColor;c.setAlpha(c.alpha() * oldProp); // 旧文字渐渐消失painter.setPen(c);painter.drawText(QRect(-w2,-h2,width(),height()), Qt::AlignCenter, prevCh);c = this->color;c.setAlpha(c.alpha() * newProp); // 新文字渐渐显示painter.setPen(c);painter.drawText(QRect(-w2, -h2, width(), height()), Qt::AlignCenter, ch);painter.restore();
}void CaptchaMovableLabel::mousePressEvent(QMouseEvent *ev)
{if (ev->button() == Qt::LeftButton){// 开始拖拽press_pos = ev->pos();dragging = true;moved = false;this->raise();movingTimer.stop();startPressAnimation(200);return ev->accept();}QLabel::mousePressEvent(ev);
}void CaptchaMovableLabel::mouseMoveEvent(QMouseEvent *ev)
{if (dragging && ev->buttons() & Qt::LeftButton){if (!moved && (ev->pos() - press_pos).manhattanLength() < QApplication::startDragDistance()){return QLabel::mouseMoveEvent(ev); // 还没到这时候}moved = true;move(this->pos() + ev->pos() - press_pos);ev->accept();return ;}QLabel::mouseMoveEvent(ev);
}void CaptchaMovableLabel::mouseReleaseEvent(QMouseEvent *ev)
{if (dragging){// 结束拖拽dragging = false;movingTimer.start();startPressAnimation(0);}if (moved)return ev->accept();QLabel::mouseReleaseEvent(ev);
}void CaptchaMovableLabel::startPressAnimation(int end)
{QPropertyAnimation* ani = new QPropertyAnimation(this, "pressProgress");ani->setStartValue(pressProgress);ani->setEndValue(end);ani->setDuration(CAPTCHA_REFRESH_DURATION << 1);ani->start();connect(ani, SIGNAL(finished()), ani, SLOT(deleteLater()));
}void CaptchaMovableLabel::setRefreshProgress(int g)
{this->refreshProgress = g;update();
}int CaptchaMovableLabel::getRefreshProgress()
{return refreshProgress;
}bool CaptchaMovableLabel::isNoAni()
{return refreshProgress == 100;
}void CaptchaMovableLabel::setPressProgress(int g)
{this->pressProgress = g;double off = g / 100;effect.setBlurRadius(g / 20.0);effect.setOffset(-off, off);
}int CaptchaMovableLabel::getPressProgress()
{return pressProgress;
}void CaptchaMovableLabel::slotMovePos()
{if (refreshProgress < 100)return ;int val = color.red() + moveR;if ( val > 255){val = 255;moveR = - qrand() % 5;}else if (val < 0){val = 0;moveR = - qrand() % 5;}color.setRed(val);val = color.green() + moveG;if ( val > 255){val = 255;moveG = - qrand() % 5;}else if (val < 0){val = 0;moveG = - qrand() % 5;}color.setGreen(val);val = color.blue() + moveB;if ( val > 255){val = 255;moveB = - qrand() % 5;}else if (val < 0){val = 0;moveB = - qrand() % 5;}color.setBlue(val);
}

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