一、2024 永不卡顿

爱的魔力它转圈圈~
等待样式控件是我们在做UI时出场率还挺高的控件之一，通常情况下有如下的几种实现方式：
1> 获取一张gif的资源图，然后使用QMovie 在一个QLabel 控件上加载显示gif的waiting等待动态。
2> 自定义绘图，然后使用Qt动画，达到转圈圈的效果。本文以此方式为例，给大家一个好看的样式示例。

本篇，作为搬运工：https://github.com/snowwlex/QtWaitingSpinner

二、代码示例

使用草鸡简单，提供了一些接口，用于waiting 标签的修改。

#include <QCoreApplication>
#include <QApplication>
#include <waitingspinnerwidget.h>
#include <QFrame>
#include <QHBoxLayout>

int main(int argc,char* argv[])
{
    QApplication a(argc,argv);

	
    WaitingSpinnerWidget* spinner = new WaitingSpinnerWidget;
    /// 设置waiting组件的样式
    spinner->setRoundness(70.0);
    spinner->setMinimumTrailOpacity(15.0);
    spinner->setTrailFadePercentage(70.0);
    spinner->setNumberOfLines(12);
    spinner->setLineLength(10);
    spinner->setLineWidth(5);
    spinner->setInnerRadius(10);
    spinner->setRevolutionsPerSecond(1);
    spinner->setColor(QColor(81, 4, 71));

    spinner->start(); // gets the show on the road!


    QFrame* f = new QFrame;
    QHBoxLayout* hlayout = new QHBoxLayout;
    hlayout->addWidget(spinner);
    f->setLayout(hlayout);
    f->show();

    return a.exec();
}

具体实现代码如下：

// waitingspinnerwidget.h

/* Original Work Copyright (c) 2012-2014 Alexander Turkin
   Modified 2014 by William Hallatt
   Modified 2015 by Jacob Dawid
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

#pragma once

// Qt includes
#include <QWidget>
#include <QTimer>
#include <QColor>

class WaitingSpinnerWidget : public QWidget {
    Q_OBJECT
public:
    /*! Constructor for "standard" widget behaviour - use this
   * constructor if you wish to, e.g. embed your widget in another. */
    WaitingSpinnerWidget(QWidget *parent = 0,
                         bool centerOnParent = true,
                         bool disableParentWhenSpinning = true);

    /*! Constructor - use this constructor to automatically create a modal
   * ("blocking") spinner on top of the calling widget/window.  If a valid
   * parent widget is provided, "centreOnParent" will ensure that
   * QtWaitingSpinner automatically centres itself on it, if not,
   * "centreOnParent" is ignored. */
    WaitingSpinnerWidget(Qt::WindowModality modality,
                         QWidget *parent = 0,
                         bool centerOnParent = true,
                         bool disableParentWhenSpinning = true);

public slots:
    void start();
    void stop();

public:
    void setColor(QColor color);
    void setRoundness(qreal roundness);
    void setMinimumTrailOpacity(qreal minimumTrailOpacity);
    void setTrailFadePercentage(qreal trail);
    void setRevolutionsPerSecond(qreal revolutionsPerSecond);
    void setNumberOfLines(int lines);
    void setLineLength(int length);
    void setLineWidth(int width);
    void setInnerRadius(int radius);
    void setText(QString text);

    QColor color();
    qreal roundness();
    qreal minimumTrailOpacity();
    qreal trailFadePercentage();
    qreal revolutionsPersSecond();
    int numberOfLines();
    int lineLength();
    int lineWidth();
    int innerRadius();

    bool isSpinning() const;

private slots:
    void rotate();

protected:
    void paintEvent(QPaintEvent *paintEvent);

private:
    static int lineCountDistanceFromPrimary(int current, int primary,
                                            int totalNrOfLines);
    static QColor currentLineColor(int distance, int totalNrOfLines,
                                   qreal trailFadePerc, qreal minOpacity,
                                   QColor color);

    void initialize();
    void updateSize();
    void updateTimer();
    void updatePosition();

private:
    QColor  _color;
    qreal   _roundness; // 0..100
    qreal   _minimumTrailOpacity;
    qreal   _trailFadePercentage;
    qreal   _revolutionsPerSecond;
    int     _numberOfLines;
    int     _lineLength;
    int     _lineWidth;
    int     _innerRadius;

private:
    WaitingSpinnerWidget(const WaitingSpinnerWidget&);
    WaitingSpinnerWidget& operator=(const WaitingSpinnerWidget&);

    QTimer *_timer;
    bool    _centerOnParent;
    bool    _disableParentWhenSpinning;
    int     _currentCounter;
    bool    _isSpinning;
};

// waitingspinnerwidget.cpp


/* Original Work Copyright (c) 2012-2014 Alexander Turkin
   Modified 2014 by William Hallatt
   Modified 2015 by Jacob Dawid

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

// Own includes
#include "waitingspinnerwidget.h"

// Standard includes
#include <cmath>
#include <algorithm>

// Qt includes
#include <QPainter>
#include <QTimer>

WaitingSpinnerWidget::WaitingSpinnerWidget(QWidget *parent,
                                           bool centerOnParent,
                                           bool disableParentWhenSpinning)
    : QWidget(parent),
      _centerOnParent(centerOnParent),
      _disableParentWhenSpinning(disableParentWhenSpinning) {
    initialize();
}

WaitingSpinnerWidget::WaitingSpinnerWidget(Qt::WindowModality modality,
                                           QWidget *parent,
                                           bool centerOnParent,
                                           bool disableParentWhenSpinning)
    : QWidget(parent, Qt::Dialog | Qt::FramelessWindowHint),
      _centerOnParent(centerOnParent),
      _disableParentWhenSpinning(disableParentWhenSpinning){
    initialize();

    // We need to set the window modality AFTER we've hidden the
    // widget for the first time since changing this property while
    // the widget is visible has no effect.
    setWindowModality(modality);
    setAttribute(Qt::WA_TranslucentBackground);
}

void WaitingSpinnerWidget::initialize() {
    _color = Qt::black;
    _roundness = 100.0;
    _minimumTrailOpacity = 3.14159265358979323846;
    _trailFadePercentage = 80.0;
    _revolutionsPerSecond = 1.57079632679489661923;
    _numberOfLines = 20;
    _lineLength = 10;
    _lineWidth = 2;
    _innerRadius = 10;
    _currentCounter = 0;
    _isSpinning = false;

    _timer = new QTimer(this);
    connect(_timer, SIGNAL(timeout()), this, SLOT(rotate()));
    updateSize();
    updateTimer();
    hide();
}

void WaitingSpinnerWidget::paintEvent(QPaintEvent *) {
    updatePosition();
    QPainter painter(this);
    painter.fillRect(this->rect(), Qt::transparent);
    painter.setRenderHint(QPainter::Antialiasing, true);

    if (_currentCounter >= _numberOfLines) {
        _currentCounter = 0;
    }

    painter.setPen(Qt::NoPen);
    for (int i = 0; i < _numberOfLines; ++i) {
        painter.save();
        painter.translate(_innerRadius + _lineLength,
                          _innerRadius + _lineLength);
        qreal rotateAngle =
                static_cast<qreal>(360 * i) / static_cast<qreal>(_numberOfLines);
        painter.rotate(rotateAngle);
        painter.translate(_innerRadius, 0);
        int distance =
                lineCountDistanceFromPrimary(i, _currentCounter, _numberOfLines);
        QColor color =
                currentLineColor(distance, _numberOfLines, _trailFadePercentage,
                                 _minimumTrailOpacity, _color);
        painter.setBrush(color);
        // TODO improve the way rounded rect is painted
        painter.drawRoundedRect(
                    QRect(0, -_lineWidth / 2, _lineLength, _lineWidth), _roundness,
                    _roundness, Qt::RelativeSize);
        painter.restore();
    }
}

void WaitingSpinnerWidget::start() {
    updatePosition();
    _isSpinning = true;
    show();

    if(parentWidget() && _disableParentWhenSpinning) {
        parentWidget()->setEnabled(false);
    }

    if (!_timer->isActive()) {
        _timer->start();
        _currentCounter = 0;
    }
}

void WaitingSpinnerWidget::stop() {
    _isSpinning = false;
    hide();

    if(parentWidget() && _disableParentWhenSpinning) {
        parentWidget()->setEnabled(true);
    }

    if (_timer->isActive()) {
        _timer->stop();
        _currentCounter = 0;
    }
}

void WaitingSpinnerWidget::setNumberOfLines(int lines) {
    _numberOfLines = lines;
    _currentCounter = 0;
    updateTimer();
}

void WaitingSpinnerWidget::setLineLength(int length) {
    _lineLength = length;
    updateSize();
}

void WaitingSpinnerWidget::setLineWidth(int width) {
    _lineWidth = width;
    updateSize();
}

void WaitingSpinnerWidget::setInnerRadius(int radius) {
    _innerRadius = radius;
    updateSize();
}

QColor WaitingSpinnerWidget::color() {
    return _color;
}

qreal WaitingSpinnerWidget::roundness() {
    return _roundness;
}

qreal WaitingSpinnerWidget::minimumTrailOpacity() {
    return _minimumTrailOpacity;
}

qreal WaitingSpinnerWidget::trailFadePercentage() {
    return _trailFadePercentage;
}

qreal WaitingSpinnerWidget::revolutionsPersSecond() {
    return _revolutionsPerSecond;
}

int WaitingSpinnerWidget::numberOfLines() {
    return _numberOfLines;
}

int WaitingSpinnerWidget::lineLength() {
    return _lineLength;
}

int WaitingSpinnerWidget::lineWidth() {
    return _lineWidth;
}

int WaitingSpinnerWidget::innerRadius() {
    return _innerRadius;
}

bool WaitingSpinnerWidget::isSpinning() const {
    return _isSpinning;
}

void WaitingSpinnerWidget::setRoundness(qreal roundness) {
    _roundness = std::max(0.0, std::min(100.0, roundness));
}

void WaitingSpinnerWidget::setColor(QColor color) {
    _color = color;
}

void WaitingSpinnerWidget::setRevolutionsPerSecond(qreal revolutionsPerSecond) {
    _revolutionsPerSecond = revolutionsPerSecond;
    updateTimer();
}

void WaitingSpinnerWidget::setTrailFadePercentage(qreal trail) {
    _trailFadePercentage = trail;
}

void WaitingSpinnerWidget::setMinimumTrailOpacity(qreal minimumTrailOpacity) {
    _minimumTrailOpacity = minimumTrailOpacity;
}

void WaitingSpinnerWidget::rotate() {
    ++_currentCounter;
    if (_currentCounter >= _numberOfLines) {
        _currentCounter = 0;
    }
    update();
}

void WaitingSpinnerWidget::updateSize() {
    int size = (_innerRadius + _lineLength) * 2;
    setFixedSize(size, size);
}

void WaitingSpinnerWidget::updateTimer() {
    _timer->setInterval(1000 / (_numberOfLines * _revolutionsPerSecond));
}

void WaitingSpinnerWidget::updatePosition() {
    if (parentWidget() && _centerOnParent) {
        move(parentWidget()->width() / 2 - width() / 2,
             parentWidget()->height() / 2 - height() / 2);
    }
}

int WaitingSpinnerWidget::lineCountDistanceFromPrimary(int current, int primary,
                                                       int totalNrOfLines) {
    int distance = primary - current;
    if (distance < 0) {
        distance += totalNrOfLines;
    }
    return distance;
}

QColor WaitingSpinnerWidget::currentLineColor(int countDistance, int totalNrOfLines,
                                              qreal trailFadePerc, qreal minOpacity,
                                              QColor color) {
    if (countDistance == 0) {
        return color;
    }
    const qreal minAlphaF = minOpacity / 100.0;
    int distanceThreshold =
            static_cast<int>(ceil((totalNrOfLines - 1) * trailFadePerc / 100.0));
    if (countDistance > distanceThreshold) {
        color.setAlphaF(minAlphaF);
    } else {
        qreal alphaDiff = color.alphaF() - minAlphaF;
        qreal gradient = alphaDiff / static_cast<qreal>(distanceThreshold + 1);
        qreal resultAlpha = color.alphaF() - gradient * countDistance;

        // If alpha is out of bounds, clip it.
        resultAlpha = std::min(1.0, std::max(0.0, resultAlpha));
        color.setAlphaF(resultAlpha);
    }
    return color;
}

三、祝愿

本章代码小而美，生活中也有无数个小美好。
祝愿朋友们：
		新年一路向上！
		事业永不卡顿！
		共赴美好，开启新征程~