如何一次一个滚动绘制每个SVG路径(按时间顺序)

How to scroll draw each SVG path one at a time (chronologically)?

本文关键字：路径 SVG 顺序 时间 滚动 何一次 一个 绘制      更新时间：2023-09-26

这与之前的一篇文章有关。然而，我认为这是一项艰巨的任务。所以我把它分解成更小的块。

我制作了一个简单的SVG图像，其中包括一个"路径"和一个"矩形"元素。用户可以通过上下滚动页面来绘制窗口上和窗口外的线条(打开时向下滚动页面，关闭/"绘制"时向上滚动页面)。然而，这两个元素是同时"绘制"/动画的。我想做的是，当用户向下滚动页面时，线条路径绘制在上面，然后"rect"元素绘制(在后面)，因此它更流畅，更按时间顺序。

 <!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>the single line</title>
<link rel="stylesheet" type="text/css" href="line.css">
<style>
svg {
  position: fixed;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  width: 50%;
}
/*.line{
  stroke-dashoffset:850;
  stroke-dasharray: 850;
}
.box {
 stroke-dashoffset:1852;
 stroke-dasharray: 1852;
}*/
.all{
 stroke-dashoffset:2702;
 stroke-dasharray: 2702;
}
.straightLine {
  height: 3000px;
  position: relative;
  width: 360px;    
  margin: 40vh auto 0 auto;
}
</style>
</head>
<body>
<main role="article" title="line">
<div class="straightLine">
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
     viewBox="0 0 1280 800" style="enable-background:new 0 0 1280 800;" xml:space="preserve">
<style type="text/css">
    .st0{fill:none;stroke:#000000;stroke-width:8;stroke-miterlimit:10;}
</style>
<g class="all">
<path class="st0" d="M54,178h509.6c49.9,0,90.4,40.5,90.4,90.4V428"/>

<rect x="498" y="428" class="st0" width="308" height="162"/>
</g>
</svg>

</div>
</main>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script src="line.js"></script>
<script>
$(document).ready(function() {
  //variable for the 'stroke-dashoffset' unit
  var $dashOffset = $(".all").css("stroke-dashoffset");
  //on a scroll event - execute function
  $(window).scroll(function() {
    //calculate how far down the page the user is 
    var $percentageComplete = (($(window).scrollTop() / ($("html").height() - $(window).height())) * 100);
    //convert dashoffset pixel value to interger
    var $newUnit = parseInt($dashOffset, 10);
    //get the value to be subtracted from the 'stroke-dashoffset'
    var $offsetUnit = $percentageComplete * ($newUnit / 100);
    //set the new value of the dashoffset to create the drawing effect
    $(".all").css("stroke-dashoffset", $newUnit - $offsetUnit);
  });
});
</script>
</body>
</html>

这是怎么回事?您可以通过设置scrollBehaviour数组中的startPct和endPct百分比值来控制每条路径何时开始和完成绘制。

注意:此代码假设您只使用路径和rects。如果您开始使用其他元素，则必须更新calcPathLength()函数。

var scrollBehaviour = [
     {id: 'line1', startPct: 0, endPct: 30},
     {id: 'rect1', startPct: 30, endPct: 60},
     {id: 'line2', startPct: 60, endPct: 80},
     {id: 'circ1', startPct: 80, endPct: 100}
  ];
$(document).ready(function() {
  // On a scroll event - execute function
  $(window).scroll(scrollEventHandler);
  // Call the scroll event handler once at the start to initialise the dash offsets
  scrollEventHandler();
});
function scrollEventHandler()
{
  // Calculate how far down the page the user is 
  var percentOfScroll = (($(window).scrollTop() / ($("html").height() - $(window).height())) * 100);
  // For each lement that is getting drawn...
  for (var i=0; i<scrollBehaviour.length; i++)
  {
    var data = scrollBehaviour[i];
    var elem = document.getElementById(data.id);
    // Get the length of this elements path
    var dashLen = calcPathLength(elem);
    // Calculate where the current scroll position falls relative to our path
    var fractionThroughThisElem = (percentOfScroll - data.startPct) / (data.endPct - data.startPct);
    // Clamp the fraction value to within this path (0 .. 1)
    fractionThroughThisElem = Math.max(fractionThroughThisElem, 0);
    fractionThroughThisElem = Math.min(fractionThroughThisElem, 1);
    var dashOffset = dashLen * (1 - fractionThroughThisElem);
    elem.setAttribute("stroke-dasharray", dashLen);
    elem.setAttribute("stroke-dashoffset", dashOffset);
  }
}
function calcPathLength(elem)
{
  if (elem.getTotalLength)
  {
    // It's a path
    return elem.getTotalLength();
  }
  else if (elem.tagName === "rect")
  {
    // Handle rect elements: perimeter length = w + w + h + h
    return (elem.width.baseVal.value + elem.height.baseVal.value) * 2;
  }
  else if (elem.tagName === "circle")
  {
    // Handle circle elements: perimeter length = 2 * r * PI
    return elem.r.baseVal.value * 2 * Math.PI;
  }
  else if (elem.tagName === "line")
  {
    // Handle line elements: use pythagoras' theorem
    var dx = elem.x2.baseVal.value - elem.x1.baseVal.value;
    var dy = elem.y2.baseVal.value - elem.y1.baseVal.value;
    return Math.sqrt(dx * dx + dy * dy);
  }
  // If you use other elem types, you will have to add support for them here.
}
svg {
  position: fixed;
  margin: auto;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  width: 50%;
}
/*.line{
  stroke-dashoffset:850;
  stroke-dasharray: 850;
}
.box {
 stroke-dashoffset:1852;
 stroke-dasharray: 1852;
}
.all{
 stroke-dashoffset:2702;
 stroke-dasharray: 2702;
}*/
.straightLine {
  height: 3000px;
  position: relative;
  width: 360px;    
  margin: 40vh auto 0 auto;
}
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<main role="article" title="line">
<div class="straightLine">
<svg version="1.1" id="Layer_1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" x="0px" y="0px"
     viewBox="0 0 1280 1000" style="enable-background:new 0 0 1280 800;" xml:space="preserve">
<style type="text/css">
    .st0{fill:none;stroke:#000000;stroke-width:8;stroke-miterlimit:10;}
</style>
  <g class="all">
    <path id="line1" class="st0" d="M54,178h509.6c49.9,0,90.4,40.5,90.4,90.4V428"/>
    <rect id="rect1" x="498" y="428" class="st0" width="308" height="162"/>
    <line id="line2" x1="652" y1="590" x2="652" y2="790" class="st0"/>
    <circle id="circ1" cx="652" cy="890" r="100" class="st0"/>
  </g>
</svg>
</div>
</main>

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