我在一个html 5画布上工作,并在它上画圆,但是当我试图使用一个循环都消失了。 [英] I am working on an html 5 canvas and tying to draw circles on it, but as I trying to use a loop all disappears.
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问题描述
所有好的,直到我试图把for循环(无论我打算使用循环)。对不起的麻烦帮助请
< canvas id =MyCanvaswidth =400height =400
style =border:1px solid#000000;>
< / canvas>
< script>
function(){
var c = document.getElementById(MyCanvas);
var ctx = c.getContext(2d);
ctx.beginPath();
ctx.arc(200,200,200,0,2 * Math.PI);
ctx.stroke();
ctx.beginPath();
ctx.arc(200,010,0,2 * Math.PI);
ctx.stroke();
for(int i = 0; i <2; i ++){
return i;}
}
< / script>
方案
这是您的代码重构:
-
:
var circle1 = {x:200,y:200,radius:200}
var circle2 = {x:200,y:0,radius:10};
-
将所有圆形对象保存在数组中: / p>
var circles = [];
circles.push(circle1);
circles.push(circle2);
-
创建一个从指定的圆形对象中绘制1个圆的函数: / strong>
function drawCircle(circle){
ctx.beginPath
ctx.arc(circle.x,circle.y,circle.radius,0,2 * Math.PI);
ctx.closePath();
ctx.stroke();
}
-
创建一个函数,所有圈子:
function drawAll(){
for(var i = 0; i& circle.length; i ++){
drawCircle(circles [i]);
}
}
将它们放在一起...这是一个演示:
var c = document.getElementById(canvas ); var ctx = c.getContext(2d); var cw = canvas.width; var ch = canvas.height; var circles = []; circles.push({x:200,y:200,radius:200 }; circle.push({x:200,y:0,radius:10}); drawAll(); function drawAll(){for(var i = 0; i
body {background-color :象牙} canvas {border:1px solid red;}
canvas id =canvaswidth = 400 height = 400>< / canvas>
All good until I trying to put the for loop in(no matter what I am meant to use the loop for). Sorry for the dumb quesion help please
<canvas id="MyCanvas" width="400" height="400"
style="border:1px solid #000000;">
</canvas>
<script>
function(){
var c = document.getElementById("MyCanvas");
var ctx = c.getContext("2d");
ctx.beginPath();
ctx.arc(200,200,200,0,2*Math.PI);
ctx.stroke();
ctx.beginPath();
ctx.arc(200,0,10,0,2*Math.PI);
ctx.stroke();
for(int i=0; i<2; i++){
return i;}
}
</script>
解决方案
Here is your code refactored:
Save each circle definition in a javascript object:
var circle1={x:200,y:200,radius:200}; var circle2={x:200,y:0,radius:10};
Save all the circle-objects in an array:
var circles=[]; circles.push(circle1); circles.push(circle2);
Create a function that draws 1 circle from a specified circle-object:
function drawCircle(circle){ ctx.beginPath(); ctx.arc(circle.x,circle.y,circle.radius,0,2*Math.PI); ctx.closePath(); ctx.stroke(); }
Create a function that iterates through the array and draws all the circles:
function drawAll(){ for(var i=0;i<circles.length;i++){ drawCircle(circles[i]); } }
Putting it all together...Here's a demo:
var c=document.getElementById("canvas");
var ctx=c.getContext("2d");
var cw=canvas.width;
var ch=canvas.height;
var circles=[];
circles.push({x:200,y:200,radius:200});
circles.push({x:200,y:0,radius:10});
drawAll();
function drawAll(){
for(var i=0;i<circles.length;i++){
drawCircle(circles[i]);
}
}
function drawCircle(circle){
ctx.beginPath();
ctx.arc(circle.x,circle.y,circle.radius,0,2*Math.PI);
ctx.closePath();
ctx.stroke();
}
body{ background-color: ivory; }
canvas{border:1px solid red;}
<canvas id="canvas" width=400 height=400></canvas>
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