Canvas How to - Start and stop an animation via button

Question

We would like to know how to start and stop an animation via button.
Answer


<!--  w  w  w .  j a  v  a2s .  c  o  m-->


<!DOCTYPE html>

<html>
  <head>
    <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
    <script type="text/javascript">
      $(document).ready(function() {  
        var canvas = $("#myCanvas");
        var context = canvas.get(0).getContext("2d");
        
        var canvasWidth = canvas.width();
        var canvasHeight = canvas.height();
        
        var playAnimation = true;
        var x = 0;
        
        var startButton = $("#startAnimation");
        var stopButton = $("#stopAnimation");
        
        startButton.hide();
        startButton.click(function() {
          $(this).hide();
          stopButton.show();
          
          playAnimation = true;
          animate();
        });
        
        stopButton.click(function() {
          $(this).hide();
          startButton.show();
          
          playAnimation = false;
        });
        
        // Animation loop that does all the fun stuff
        function animate() {
          // Update
          x++;
          
          // Clear
          context.clearRect(0, 0, canvasWidth, canvasHeight);
          
          // Draw
          context.fillRect(x, 250, 10, 10);
          
          if (playAnimation) {
            // Run the animation loop again in 33 milliseconds
            setTimeout(animate, 33);
          };
        };
        
        // Start the animation loop
        animate();
      });
    </script>
  </head>
  
  <body>
    <canvas id="myCanvas" width="500" height="500">
      <!-- Insert fallback content here -->
    </canvas>
    <div>
      <button id="startAnimation">Start</button>
      <button id="stopAnimation">Stop</button>
    </div>
  </body>
</html>
The code above is rendered as follows: