使滚动增长 <path> 到虚线

Posted 2023-03-06

【中文标题】使滚动增长 <path> 到虚线

【英文标题】：Make the on scroll growing <path> to dashed line

【发布时间】：2018-01-14 08:40:29

【问题描述】：

这是我目前在 stackoverfow 本身的朋友的帮助下所做的。

效果很好，但我想做一个对我来说有点复杂的动画。

// Get the id of the <path> element and the length of <path>
var myline = document.getElementById("myline");
var length = myline.getTotalLength();
circle = document.getElementById("circle");
// The start position of the drawing
myline.style.strokeDasharray = length;

// Hide the triangle by offsetting dash. Remove this line to show the triangle before scroll draw
myline.style.strokeDashoffset = length;

// Find scroll percentage on scroll (using cross-browser properties), and offset dash same amount as percentage scrolled
window.addEventListener("scroll", myFunction);

function myFunction() 
  // What % down is it?
  var scrollpercent = (document.body.scrollTop + document.documentElement.scrollTop) / (document.documentElement.scrollHeight - document.documentElement.clientHeight);
  // Length to offset the dashes
  var draw = length * scrollpercent;

  // Reverse the drawing (when scrolling upwards)
  myline.style.strokeDashoffset = length - draw;

  //get point at length
  endPoint = myline.getPointAtLength(draw);
  circle.setAttribute("cx", endPoint.x);
  circle.setAttribute("cy", endPoint.y);

body 
  height: 2000px;
  background: #f1f1f1;


#circle 
  fill: red;


#mySVG 
  position: fixed;
  top: 15%;
  width: 100vw;
  height: 100vh;
  margin-left: -50px;


.st0 
  fill: none;
  stroke-dashoffset: 3px;
  stroke: red;
  stroke-width: 5;
  stroke-miterlimit: 10;
  stroke-dasharray: 20;

<h2>Scroll down this window to draw my path.</h2>
<p>Scroll back up to reverse the drawing.</p>

<svg id="mySVG" viewBox="0 0 60 55" preserveAspectRatio="xMidYMin slice" style="width: 6%; padding-bottom: 42%; height: 1px; overflow: visible">
  <circle id="circle" cx="10" cy="10" r="10"/>
  <path id="myline" class="st0" stroke-dasharray="10,9" d="M 20 0 v 20 a 30 30 0 0 0 30 30 h 600 a 40 40 0 0 1 0 80 h -140 a 30 30 0 0 0 0 60 h 200 a 40 40 0 0 1 0 80 h -100 a 30 30 0 0 0 -30 30 v 20" /> Sorry, your browser does not support inline SVG.
</svg>

我的问题是我们可以画虚线吗？

我知道使用strokeDasharray 的路径正在增长。但是，有没有办法达到我正在寻找的东西？如果没有，那么请建议另一种方式。我不是在寻找“在您要绘制的线条上放置一条虚线并为其提供背景颜色”。

【问题讨论】：

我不相信有别的办法，除了你说你不想要的codepen.io/Evgeny/pen/IEGoq

@KScandrett 在我的在线检查中也是我得出的结论。但我想知道是否有人尝试过新方法并到达某个地方。让我们看看有没有人有新的想法..！

【参考方案1】：

有一种方法可以做到这一点。您可以使用虚线作为动画线的遮罩。

// Get the id of the <path> element and the length of <path>
var myline = document.getElementById("myline");
var length = myline.getTotalLength();
circle = document.getElementById("circle");
// The start position of the drawing
myline.style.strokeDasharray = length;

// Hide the triangle by offsetting dash. Remove this line to show the triangle before scroll draw
myline.style.strokeDashoffset = length;

// Find scroll percentage on scroll (using cross-browser properties), and offset dash same amount as percentage scrolled
window.addEventListener("scroll", myFunction);

function myFunction() 
  // What % down is it?
  var scrollpercent = (document.body.scrollTop + document.documentElement.scrollTop) / (document.documentElement.scrollHeight - document.documentElement.clientHeight);
  // Length to offset the dashes
  var draw = length * scrollpercent;

  // Reverse the drawing (when scrolling upwards)
  myline.style.strokeDashoffset = length - draw;

  //get point at length
  endPoint = myline.getPointAtLength(draw);
  circle.setAttribute("cx", endPoint.x);
  circle.setAttribute("cy", endPoint.y);

body 
  height: 2000px;
  background: #f1f1f1;


#circle 
  fill: red;


#mySVG 
  position: fixed;
  top: 15%;
  width: 100vw;
  height: 100vh;
  margin-left: -50px;


.st0 
  fill: none;
  stroke-dashoffset: 3px;
  stroke: red;
  stroke-width: 5;
  stroke-miterlimit: 10;
  stroke-dasharray: 20;


.mask-style 
  stroke: white;
  stroke-width: 7;

<h2>Scroll down this window to draw my path.</h2>
<p>Scroll back up to reverse the drawing.</p>

<svg id="mySVG" viewBox="0 0 60 55" preserveAspectRatio="xMidYMin slice" style="width: 6%; padding-bottom: 42%; height: 1px; overflow: visible">
  <defs>
    <mask id="dash-mask">
      <path class="st0 mask-style" stroke-dasharray="10,9" d="M 20 0 v 20 a 30 30 0 0 0 30 30 h 600 a 40 40 0 0 1 0 80 h -140 a 30 30 0 0 0 0 60 h 200 a 40 40 0 0 1 0 80 h -100 a 30 30 0 0 0 -30 30 v 20" />
    </mask>
  </defs>
  <circle id="circle" cx="10" cy="10" r="10"/>
  <path id="myline" class="st0" stroke-dasharray="10,9" d="M 20 0 v 20 a 30 30 0 0 0 30 30 h 600 a 40 40 0 0 1 0 80 h -140 a 30 30 0 0 0 0 60 h 200 a 40 40 0 0 1 0 80 h -100 a 30 30 0 0 0 -30 30 v 20" mask="url(#dash-mask)"/>
  Sorry, your browser does not support inline SVG.
</svg>

【讨论】：

Nyz 这是一个很好的解决方法。但我想知道是否有任何直接的方法可以做到这一点。！

变通方法是针对错误的 hacky 解决方案。这不是那个。您复制路径。让它变白，稍微厚一点。将其包裹在<mask> 标签中，然后将您的原始路径指向它。这一点都不复杂。你不会找到更简单的解决方案。