html5-canvas - 为什么我不能在我的 HTML5 Canvas 中绘制两条不同颜色的线？

Question

我正在尝试使用 HTML5 Canvas 在绿线的左侧绘制一条红线。这是我的javascript:

var canvas = document.createElement('canvas');
canvas.height = 150;
canvas.width = 150;
var canvasContext = canvas.getContext('2d');
canvasContext.beginPath();

// Draw the red line.
canvasContext.strokeStyle = '#f00';
canvasContext.moveTo(10, 0);
canvasContext.lineTo(10, 100);
canvasContext.stroke();

// Draw the green line.
canvasContext.moveTo(50, 0);
canvasContext.strokeStyle = '#0f0';
canvasContext.lineTo(50, 100);
canvasContext.stroke();

document.body.appendChild(canvas);​

但是，在 Google Chrome 中，我在浅绿色线的左侧看到了一条深绿色线。为什么？我叫了stroke两次对吧？因此，为什么我的第一次中风会影响我的第二次？

Here是一个 JSFiddle，说明了我的意思。

Answer 1

你没有调用 canvasContext.beginPath();当你开始画第二条线时。

为了使绘图部分更加独立，我添加了空格:

var canvas = document.createElement('canvas');
canvas.height = 150;
canvas.width = 150;

var canvasContext = canvas.getContext('2d');

// Draw the red line.
canvasContext.beginPath();
canvasContext.strokeStyle = '#f00';
canvasContext.moveTo(10, 0);
canvasContext.lineTo(10, 100);
canvasContext.stroke();

// Draw the green line.
canvasContext.beginPath();
canvasContext.moveTo(50, 0);
canvasContext.strokeStyle = '#0f0';
canvasContext.lineTo(50, 100);
canvasContext.stroke();

document.body.appendChild(canvas); 

演示:http://jsfiddle.net/AhdJr/2/