I have a small program that I am supposed to write that makes a bouncy ball in a canvas. I can get a wireframe of a ball bouncing, but can’t seem to get the setTimeout to fire at all. I have read, read and read about the function, but can’t figure this out (new).
<!DOCTYPE HTML>
<html>
<head>
<title>basic Canvas</title>
<style>
#canvas1{
border:1px solid #9C9898;
}
body{
margin:0px;
padding:0px;
}
</style>
<script>
function drawMe(){
//Set x,y,radius
var x = 60;
var y = 60;
var radius = 70;
drawLoop(x,y,radius);
}
function drawLoop(x,y,radius){
var canvas2=document.getElementById("canvas1");
var ctx=canvas2.getContext("2d");
for(i=1;i<100;i++){
if(y + radius >= canvas2.height){
d = 1;
}
if(y - radius <= 0){
d = 0;
}
if (d==0){
x = x + 10;
y = y + 10;
}
else if (d==1){
x = x + 10;
y = y - 10;
}
draw(x,y,radius);
window.setTimeout(function() {draw(x,y,radius)},3000);
}
}
function draw(x,y,radius){
var canvas2=document.getElementById("canvas1");
var ctx=canvas2.getContext("2d");
ctx.beginPath();
ctx.arc(x,y,radius,0,2*Math.PI,false);
var gradient = ctx.createRadialGradient(x, y, 1, x, y, radius);
gradient.addColorStop(0,"blue");
gradient.addColorStop(1,"white");
ctx.fillStyle=gradient;
ctx.lineWidth=1;
ctx.strokeStyle="blue";
ctx.fill();
ctx.stroke();
}
</script>
</head>
<body onload="drawMe()">
<canvas id="canvas1" width=1000" height="400">
</canvas>
</body>
</html>
A little function called ‘drawMe()’ which sets x, y, and radius, then calls a little drawing loop that fires 100 times that draws the bouncy ball (‘drawLoop’). at the bottom of the function drawLoop, I call draw, which actually drawls the circles. From what I’ve read, the line ‘setTimeout(function(){draw(x,y,radius)};,3000); should call the draw function every three seconds. But it doesn’t. What the heck am I doing wrong?
setTimeouts are counted from the time they are created. The loop runs almost instantly and creates the setTimeouts at almost the same time. They are then all ran 3 seconds later.
One way to get around this is in the solution below. This does not increment the loop until the current timeout has been completed.
http://jsfiddle.net/x8PWg/14/
This is only one of the many potential solutions to this.