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---
title: CanvasRenderingContext2D.setLineDash()
slug: Web/API/CanvasRenderingContext2D/setLineDash
tags:
- API
- Canvas
- CanvasRenderingContext2D
- Dashes
- LInes
- Method
- setLineDash
translation_of: Web/API/CanvasRenderingContext2D/setLineDash
---
<div>{{APIRef}}</div>
<p>Canvas 2D API的{{domxref("CanvasRenderingContext2D")}}接口的<strong><code>setLineDash()</code></strong>方法在填充线时使用虚线模式。 它使用一组值来指定描述模式的线和间隙的交替长度。</p>
<div class="blockIndicator note">
<p><strong>提示：</strong>如果要切换回至实线模式，将 dash list 设置为一个空数组即可。</p>
</div>
<h2 id="语法">语法</h2>
<pre class="syntaxbox">void <var><em>ctx</em>.setLineDash(segments);</var>
</pre>
<h3 id="参数">参数</h3>
<dl>
<dt><code>segments</code></dt>
<dd>一个{{jsxref("Array")}}数组。一组描述交替绘制线段和间距（坐标空间单位）长度的数字。 如果数组元素的数量是奇数， 数组的元素会被复制并重复。例如， <code>[5, 15, 25]</code> 会变成 <code>[5, 15, 25, 5, 15, 25]。</code></dd>
<dt>
<h3 id="返回值">返回值</h3>
</dt>
<dd>{{jsxref("undefined")}}</dd>
</dl>
<h2 id="示例">示例</h2>
<h3 id="基本示例">基本示例</h3>
<p>这是一段简单的代码片段，使用 <code>setLineDash</code> 方法绘制一条线段。</p>
<h4 id="HTML">HTML</h4>
<pre class="brush: html"><canvas id="canvas"></canvas>
</pre>
<h4 id="JavaScript">JavaScript</h4>
<pre class="brush: js">const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
// Dashed line
ctx.beginPath();
ctx.setLineDash([5, 15]);
ctx.moveTo(0, 50);
ctx.lineTo(300, 50);
ctx.stroke();
// Solid line
ctx.beginPath();
ctx.setLineDash([]);
ctx.moveTo(0, 100);
ctx.lineTo(300, 100);
ctx.stroke();
</pre>
<h4 id="结果">结果</h4>
<div style="display: none;">
<h6 id="Playable_code">Playable code</h6>
<pre class="brush: html"><canvas id="canvas" width="400" height="200" class="playable-canvas"></canvas>
<div class="playable-buttons">
<input id="edit" type="button" value="Edit" />
<input id="reset" type="button" value="Reset" />
</div>
<textarea id="code" class="playable-code">
ctx.setLineDash([5, 15]);
ctx.beginPath();
ctx.moveTo(0,100);
ctx.lineTo(400, 100);
ctx.stroke();</textarea>
</pre>
<pre class="brush: js">var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var textarea = document.getElementById("code");
var reset = document.getElementById("reset");
var edit = document.getElementById("edit");
var code = textarea.value;
function drawCanvas() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
eval(textarea.value);
}
reset.addEventListener("click", function() {
textarea.value = code;
drawCanvas();
});
edit.addEventListener("click", function() {
textarea.focus();
})
textarea.addEventListener("input", drawCanvas);
window.addEventListener("load", drawCanvas);
</pre>
</div>
<p>{{ EmbedLiveSample('基本示例', 700, 360) }}</p>
<h3 id="一些常见的模式">一些常见的模式</h3>
<p>此示例说明了各种常见的线划线模式。</p>
<h4 id="HTML_2">HTML</h4>
<pre class="brush: html"><code><canvas id="canvas"></canvas></code></pre>
<h4 id="JavaScript_2">JavaScript</h4>
<p>下面创建的<code>drawDashedLine()</code> 函数使得多个虚线的绘制变得简单。它接收模式数组作为其唯一参数。</p>
<pre class="brush: js">function drawDashedLine(pattern) {
ctx.beginPath();
ctx.setLineDash(pattern);
ctx.moveTo(0, y);
ctx.lineTo(300, y);
ctx.stroke();
y += 20;
}
const canvas = document.getElementById('canvas');
const ctx = canvas.getContext('2d');
let y = 15;
drawDashedLine([]);
drawDashedLine([1, 1]);
drawDashedLine([10, 10]);
drawDashedLine([20, 5]);
drawDashedLine([15, 3, 3, 3]);
drawDashedLine([20, 3, 3, 3, 3, 3, 3, 3]);
drawDashedLine([12, 3, 3]); // Equals [12, 3, 3, 12, 3, 3]</pre>
<h4 id="Result">Result</h4>
<p>{{ EmbedLiveSample('一些常见的模式', 700, 180) }}</p>
<h2 id="规范描述">规范描述</h2>
<table class="standard-table">
<tbody>
<tr>
<th scope="col">Specification</th>
<th scope="col">Status</th>
<th scope="col">Comment</th>
</tr>
<tr>
<td>{{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-setlinedash", "CanvasRenderingContext2D.setLineDash")}}</td>
<td>{{Spec2('HTML WHATWG')}}</td>
<td></td>
</tr>
</tbody>
</table>
<h2 id="浏览器兼容性">浏览器兼容性</h2>
<div class="hidden">
<p>此页面上的兼容性表是根据结构化数据生成的。 如果您想提供数据，请查看<a href="https://github.com/mdn/browser-compat-data">https://github.com/mdn/browser-compat-data</a>并向我们发送请求请求。</p>
</div>
<p>{{Compat("api.CanvasRenderingContext2D.setLineDash")}}</p>
<h2 id="参见">参见</h2>
<ul>
<li>接口定义，{{domxref("CanvasRenderingContext2D")}}</li>
<li>{{domxref("CanvasRenderingContext2D.getLineDash()")}}</li>
<li>{{domxref("CanvasRenderingContext2D.lineDashOffset")}}</li>
</ul>
|
