reactjs - 如何在 ReactJS 环境中包含 ScrollMagic 的 GreenSock 插件？

Question

如何在我的 ReactJS 项目中包含 ScrollMagic 的 Greensock 插件？

ScrollMagic 的作者制作了插件来合并 GreenSock 和 Velocity 等库。当您像这样将它们包含在 html 文档的 head 中时，它们会非常有效

<script type="text/javascript" src="js/lib/greensock/TweenMax.min.js"></script>
<script type="text/javascript" src="scrollmagic/uncompressed/ScrollMagic.js"></script>
<script type="text/javascript" src="scrollmagic/uncompressed/plugins/animation.gsap.js"></script>

但是当你使用 ReactJS 时，你不会像这样导入 javascript 资源。实际上，您必须通过 npm 命令之类的过程导入它们，然后在您的 React 项目中声明它们，如

import ScrollMagic from "scrollmagic"

虽然我能够将 ScrollMagic 导入到 React 文件中并开始使用 ScrollMagic，但我无法导入 greensock 插件。没有关于如何执行此操作的文档。我尝试通过在animation.gsap.js中提取代码段并将其粘贴到node_modules/scrollmagic/scrollmagic.js文件中来破解这些东西(编辑这些文件不是一个好主意)，但它要么破坏了 webpack 编译器，要么破坏了我的项目代码。

如何在React环境中使用greensock插件进行scrollmagic？

Answer 1

我能够构建一个包装器。在较高的层面上，我所做的是研究 plugins/animation.gsap.js 的代码，提取我需要的那些场景扩展属性，更改 namespace ，并让它增强ScrollMagic 在导出之前放在单独的 react 类中。

具体来说，我所做的是创建一个名为 ./ScrollMagic.js 的新文件并粘贴以下内容:

import ScrollMagic from 'scrollmagic';
import {TweenLite as Tween,TimelineMax as Timeline} from 'gsap';

ScrollMagic.Scene.addOption("tweenChanges", // name
  false, // default

  function (val) { // validation callback
    return !!val;
});

ScrollMagic.Scene.extend(function () {
    var Scene = this,
      _tween;

    var log = function () {
      if (Scene._log) { // not available, when main source minified
        Array.prototype.splice.call(arguments, 1, 0, "(animation.gsap)", "->");
        Scene._log.apply(this, arguments);
      }
    };

    // set listeners
    Scene.on("progress.plugin_gsap", function () {
      updateTweenProgress();
    });
    Scene.on("destroy.plugin_gsap", function (e) {
      Scene.removeTween(e.reset);
    });

    /**
     * Update the tween progress to current position.
     * @private
     */
    var updateTweenProgress = function () {
      if (_tween) {
        var
        progress = Scene.progress(),
          state = Scene.state();
        if (_tween.repeat && _tween.repeat() === -1) {
          // infinite loop, so not in relation to progress
          if (state === 'DURING' && _tween.paused()) {
            _tween.play();
          } else if (state !== 'DURING' && !_tween.paused()) {
            _tween.pause();
          }
        } else if (progress != _tween.progress()) { // do we even need to update the progress?
          // no infinite loop - so should we just play or go to a specific point in time?
          if (Scene.duration() === 0) {
            // play the animation
            if (progress > 0) { // play from 0 to 1
              _tween.play();
            } else { // play from 1 to 0
              _tween.reverse();
            }
          } else {
            // go to a specific point in time
            if (Scene.tweenChanges() && _tween.tweenTo) {
              // go smooth
              _tween.tweenTo(progress * _tween.duration());
            } else {
              // just hard set it
              _tween.progress(progress).pause();
            }
          }
        }
      }
    };

    /**
     * Add a tween to the scene.  
     * If you want to add multiple tweens, add them into a GSAP Timeline object and supply it instead (see example below).  
     * 
     * If the scene has a duration, the tween's duration will be projected to the scroll distance of the scene, meaning its progress will be synced to scrollbar movement.  
     * For a scene with a duration of `0`, the tween will be triggered when scrolling forward past the scene's trigger position and reversed, when scrolling back.  
     * To gain better understanding, check out the [Simple Tweening example](../examples/basic/simple_tweening.html).
     *
     * Instead of supplying a tween this method can also be used as a shorthand for `TweenMax.to()` (see example below).
     * @memberof! animation.GSAP#
     *
     * @example
     * // add a single tween directly
     * scene.setTween(TweenMax.to("obj"), 1, {x: 100});
     *
     * // add a single tween via variable
     * var tween = TweenMax.to("obj"), 1, {x: 100};
     * scene.setTween(tween);
     *
     * // add multiple tweens, wrapped in a timeline.
     * var timeline = new TimelineMax();
     * var tween1 = TweenMax.from("obj1", 1, {x: 100});
     * var tween2 = TweenMax.to("obj2", 1, {y: 100});
     * timeline
     *    .add(tween1)
     *    .add(tween2);
     * scene.addTween(timeline);
     *
     * // short hand to add a TweenMax.to() tween
     * scene.setTween("obj3", 0.5, {y: 100});
     *
     * // short hand to add a TweenMax.to() tween for 1 second
     * // this is useful, when the scene has a duration and the tween duration isn't important anyway
     * scene.setTween("obj3", {y: 100});
     *
     * @param {(object|string)} TweenObject - A TweenMax, TweenLite, TimelineMax or TimelineLite object that should be animated in the scene. Can also be a Dom Element or Selector, when using direct tween definition (see examples).
     * @param {(number|object)} duration - A duration for the tween, or tween parameters. If an object containing parameters are supplied, a default duration of 1 will be used.
     * @param {object} params - The parameters for the tween
     * @returns {Scene} Parent object for chaining.
     */
    Scene.setTween = function (TweenObject, duration, params) {
      var newTween;
      if (arguments.length > 1) {
        if (arguments.length < 3) {
          params = duration;
          duration = 1;
        }
        TweenObject = Tween.to(TweenObject, duration, params);
      }
      try {
        // wrap Tween into a Timeline Object if available to include delay and repeats in the duration and standardize methods.
        if (Timeline) {
          newTween = new Timeline({
            smoothChildTiming: true
          }).add(TweenObject);
        } else {
          newTween = TweenObject;
        }
        newTween.pause();
      } catch (e) {
        log(1, "ERROR calling method 'setTween()': Supplied argument is not a valid TweenObject");
        return Scene;
      }
      if (_tween) { // kill old tween?
        Scene.removeTween();
      }
      _tween = newTween;

      // some properties need to be transferred it to the wrapper, otherwise they would get lost.
      if (TweenObject.repeat && TweenObject.repeat() === -1) { // TweenMax or TimelineMax Object?
        _tween.repeat(-1);
        _tween.yoyo(TweenObject.yoyo());
      }
      // Some tween validations and debugging helpers
      if (Scene.tweenChanges() && !_tween.tweenTo) {
        log(2, "WARNING: tweenChanges will only work if the TimelineMax object is available for ScrollMagic.");
      }

      // check if there are position tweens defined for the trigger and warn about it :)
      if (_tween && Scene.controller() && Scene.triggerElement() && Scene.loglevel() >= 2) { // controller is needed to know scroll direction.
        var
        triggerTweens = Tween.getTweensOf(Scene.triggerElement()),
          vertical = Scene.controller().info("vertical");
        triggerTweens.forEach(function (value, index) {
          var
          tweenvars = value.vars.css || value.vars,
            condition = vertical ? (tweenvars.top !== undefined || tweenvars.bottom !== undefined) : (tweenvars.left !== undefined || tweenvars.right !== undefined);
          if (condition) {
            log(2, "WARNING: Tweening the position of the trigger element affects the scene timing and should be avoided!");
            return false;
          }
        });
      }

      // warn about tween overwrites, when an element is tweened multiple times
      if (parseFloat(TweenLite.version) >= 1.14) { // onOverwrite only present since GSAP v1.14.0
        var
        list = _tween.getChildren ? _tween.getChildren(true, true, false) : [_tween],
          // get all nested tween objects
          newCallback = function () {
            log(2, "WARNING: tween was overwritten by another. To learn how to avoid this issue see here: https://github.com/janpaepke/ScrollMagic/wiki/WARNING:-tween-was-overwritten-by-another");
          };
        for (var i = 0, thisTween, oldCallback; i < list.length; i++) { /*jshint loopfunc: true */
          thisTween = list[i];
          if (oldCallback !== newCallback) { // if tweens is added more than once
            oldCallback = thisTween.vars.onOverwrite;
            thisTween.vars.onOverwrite = function () {
              if (oldCallback) {
                oldCallback.apply(this, arguments);
              }
              newCallback.apply(this, arguments);
            };
          }
        }
      }
      log(3, "added tween");

      updateTweenProgress();
      return Scene;
    };

    /**
     * Remove the tween from the scene.  
     * This will terminate the control of the Scene over the tween.
     *
     * Using the reset option you can decide if the tween should remain in the current state or be rewound to set the target elements back to the state they were in before the tween was added to the scene.
     * @memberof! animation.GSAP#
     *
     * @example
     * // remove the tween from the scene without resetting it
     * scene.removeTween();
     *
     * // remove the tween from the scene and reset it to initial position
     * scene.removeTween(true);
     *
     * @param {boolean} [reset=false] - If `true` the tween will be reset to its initial values.
     * @returns {Scene} Parent object for chaining.
     */
    Scene.removeTween = function (reset) {
      if (_tween) {
        if (reset) {
          _tween.progress(0).pause();
        }
        _tween.kill();
        _tween = undefined;
        log(3, "removed tween (reset: " + (reset ? "true" : "false") + ")");
      }
      return Scene;
    };

  });

export default ScrollMagic; 

您会注意到，这看起来几乎与 plugins/animation.gsap.js 一模一样，但异常(exception)的是:

• 我在顶部添加了自己的导入行，因此请确保您提前安装了 npm rollmagic 和 gsap
• 我在最后导出 ScrollMagic 对象
• plugins/animation.gsap.js 还有一些其他代码可以将插件变成工厂，我排除了这些代码，因为它不适用于此处

现在我可以在我的 React 项目中使用 .setTween() 了。用法示例:

import React, {Component} from "react";
import ScrollMagic from "./ScrollMagic"; // my own wrapper for scrollmagic that includes greensock

export default class Home extends Component {

    componentDidMount()
    {
        var controller = new ScrollMagic.Controller();
        var item = "#whateverstuffselector";
        var scene = new ScrollMagic.Scene({triggerElement:item})
                .setTween(item, 0.5, {backgroundColor: "red", scale: 3})
                .addTo(controller);

    }

    render()
    {
        return (<div id="whateverstuffselector">stuff</div>);
    }
}