admin管理员组

文章数量:1336129

I'm trying to animate canvas using for loop and setInterval, but no luck so far... Here's what I have in my code:

//loop function
function loop(){
    var dynamic = 0;
    var v = 10;
    var x, y;

    for (dynamic = 0; dynamic < v; dynamic++) {
        x = dynamic * 1;
        y = dynamic * 1;
        c.clearRect(0, 0, 350, 350);
        c.fillStyle = '#87CEEB';
        c.beginPath();
        c.arc(x, y, 10, 0, Math.PI*2, false);
        c.fill();
    }
}

setInterval(loop, 20);

Thanks so much in advance!

I'm trying to animate canvas using for loop and setInterval, but no luck so far... Here's what I have in my code:

//loop function
function loop(){
    var dynamic = 0;
    var v = 10;
    var x, y;

    for (dynamic = 0; dynamic < v; dynamic++) {
        x = dynamic * 1;
        y = dynamic * 1;
        c.clearRect(0, 0, 350, 350);
        c.fillStyle = '#87CEEB';
        c.beginPath();
        c.arc(x, y, 10, 0, Math.PI*2, false);
        c.fill();
    }
}

setInterval(loop, 20);

Thanks so much in advance!

  • javascript
  • html5-canvas
Share Improve this question edited Jan 17, 2014 at 15:40 Jaak Kütt 2,6564 gold badges33 silver badges40 bronze badges asked Feb 25, 2013 at 16:02 shibalinkshibalink 1392 gold badges3 silver badges9 bronze badges 1
  • You're running through the entire animation loop every time loop() executes. All you'll see is the last frame of the animation. You need to execute the body of the loop only once each time the setInterval() timer fires. – Ted Hopp Commented Feb 25, 2013 at 16:17
Add a ment  | 

2 Answers 2

Reset to default 1

As said before: move your dynamic out of the animation loop and change dynamic inside the loop.

A summary of animation is this:

  1. Set your starting variables (like dynamic) outside your for loop

  2. Inside the animation loop() you want to animate the canvas by 1 move (not many moves), like this:

      + Increment your dynamic variable to induce motion.

  + Set your x & y to reflect the changes to dynamic.

  + Clear the canvas to prepare for this animation frame

  + Draw stuff!

  3. After the loop, start the animation with setInterval()

  4. If you animation runs off the screen, you might as well turn it off!

Here is some code and a Fiddle: http://jsfiddle/m1erickson/fFfRS/

<!doctype html>
<html>
<head>
<link rel="stylesheet" type="text/css" media="all" href="css/reset.css" /> <!-- reset css -->
<script type="text/javascript" src="http://code.jquery./jquery.min.js"></script>

<style>
    body{ background-color: ivory; }
    canvas{border:1px solid red;}
</style>

<script>
    $(function(){

        var canvas=document.getElementById("canvas");
        var c=canvas.getContext("2d");

        // set the dynamic outside the loop
        var dynamic = 10;
        var x;
        var y;

         //loop function
        function loop(){

            // change dynamic
           dynamic=dynamic*1.1;
           x = dynamic;
           y = dynamic*1.2;

            // stop the the animation if it runs out-of-canvas
            if (x>canvas.width || y>canvas.height){
                c.clearRect(0,0,canvas.width,canvas.height);
                clearInterval(myTimer);
                alert("animation done!");
            }

           // clear the canvas for this loop's animation
           c.clearRect(0,0,canvas.width,canvas.height);
           c.fillStyle = '#87CEEB';

           // draw
           c.beginPath();
           c.arc(x,y, 10, 0, Math.PI*2, false);
           c.fill();
        }
        var myTimer=setInterval(loop,20);       

    }); // end $(function(){});
</script>

</head>

<body>
    <canvas id="canvas" width=400 height=400></canvas>
</body>
</html>

Maybe you should move the dynamic variable to the outside? You seem to draw the circle at the same point every loop.

var dynamic = 0;
//loop function
function loop(){
  var v = 10;
  var x, y;
  x = dynamic * 1;
  y = dynamic * 1;
  c.clearRect(0,0, 350,350);
  c.fillStyle = '#87CEEB';
  c.beginPath();
  c.arc(x,y, 10, 0, Math.PI*2, false);
  c.fill();

  ++dynamic;
}

setInterval(loop,20);

本文标签： javascriptAnimate Canvas using for loop and setIntervalStack Overflow

版权声明：本文标题：javascript - Animate Canvas using for loop and setInterval - Stack Overflow 内容由网友自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：http://www.betaflare.com/web/1742373827a2462762.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。