CanvasRenderingContext2D.beginPath() 是 Canvas 2D API 通过清空子路径列表开始一个新路径的方法。 当你想创建一个新的路径时，调用此方法。
void ctx.beginPath();
beginPath 方法这是一段受用 beginPath 方法的简单的代码片段。
<canvas id="canvas"></canvas>
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
// First path
ctx.beginPath();
ctx.strokeStyle = 'blue';
ctx.moveTo(20,20);
ctx.lineTo(200,20);
ctx.stroke();
// Second path
ctx.beginPath();
ctx.strokeStyle = 'green';
ctx.moveTo(20,20);
ctx.lineTo(120,120);
ctx.stroke();
修改下面的代码并在线查看 canvas 的变化：
<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" style="height:200px"> // First path ctx.beginPath(); ctx.strokeStyle = 'blue'; ctx.moveTo(20,20); ctx.lineTo(200,20); ctx.stroke(); // Second path ctx.beginPath(); ctx.strokeStyle = 'green'; ctx.moveTo(20,20); ctx.lineTo(120, 120); ctx.stroke();</textarea>
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);
{{ EmbedLiveSample('Playable_code', 700, 460) }}
| Specification | Status | Comment |
|---|---|---|
| {{SpecName('HTML WHATWG', "scripting.html#dom-context-2d-beginpath", "CanvasRenderingContext2D.beginPath")}} | {{Spec2('HTML WHATWG')}} |