HTML5 Game - Touch events with ball movement

Description

Touch events with ball movement
Demo

<!doctype html>  
<html>  
 <head>  
  <meta name = "viewport" content="width=device-width,initial-scale=1.0,user-scalable=no">  
  <style>canvas{border:1px solid red;}</style>  
 </head>  /*from   w w  w. ja va2 s  . c  o  m*/
 <body>  
  <canvas id="canvas" width="400" height="400"></canvas>  
  <script>  
class Ball {  
constructor(radius) {
     if (radius === undefined) { radius = 40; }  
       
     this.x = 0;  
     this.y = 0;  
     this.radius = radius;  
     this.vx = 0;  
     this.vy = 0;  
     this.rotation = 0;  
     this.scaleX = 1;  
     this.scaleY = 1;  
     this.color = "#ff0000";
     this.lineWidth = 1;  
   }  
     
   draw(context) {  
     context.save();  
     context.translate(this.x, this.y);  
     context.rotate(this.rotation);  
     context.scale(this.scaleX, this.scaleY);  
     context.lineWidth = this.lineWidth;  
     context.fillStyle = this.color;  
     context.beginPath();  
     context.arc(0, 0, this.radius, 0, (Math.PI * 2), true);  
     context.closePath();  
  context.fill();  
  if (this.lineWidth > 0) {  
    context.stroke();  
  }  
  context.restore();  
}
getBounds() {  
  return {  
    x: this.x - this.radius,  
    y: this.y - this.radius,  
    width: this.radius * 2,  
    height: this.radius * 2  
  };  
}

}
containsPoint = function (rect, x, y) {  
  return !(x < rect.x || x > rect.x + rect.width ||  
           y < rect.y || y > rect.y + rect.height);  
}  
        function captureTouch(element) {
  let touch = {x: null, y: null, isPressed: false, event: null},
      body_scrollLeft = document.body.scrollLeft,
      element_scrollLeft = document.documentElement.scrollLeft,
      body_scrollTop = document.body.scrollTop,
      element_scrollTop = document.documentElement.scrollTop,
      offsetLeft = element.offsetLeft,
      offsetTop = element.offsetTop;

  element.addEventListener('touchstart', function (event) {
    touch.isPressed = true;
    touch.event = event;
  }, false);

  element.addEventListener('touchend', function (event) {
    touch.isPressed = false;
    touch.x = null;
    touch.y = null;
    touch.event = event;
  }, false);
  
  element.addEventListener('touchmove', function (event) {
    let x, y,
        touch_event = event.touches[0]; //first touch
    
    if (touch_event.pageX || touch_event.pageY) {
      x = touch_event.pageX;
      y = touch_event.pageY;
    } else {
      x = touch_event.clientX + body_scrollLeft + element_scrollLeft;
      y = touch_event.clientY + body_scrollTop + element_scrollTop;
    }
    x -= offsetLeft;
    y -= offsetTop;
    
    touch.x = x;
    touch.y = y;
    touch.event = event;
  }, false);
  
  return touch;
}
  window.onload = function () {  
    let canvas = document.getElementById('canvas'),  
        context = canvas.getContext('2d'),  
        touch = captureTouch(canvas),  
        log = document.getElementById('log'),  
        ball = new Ball();  
  
    ball.x = canvas.width / 2;  
    ball.y = canvas.height / 2;  
    ball.draw(context);  
        canvas.addEventListener('touchstart', function (event) {  
          event.preventDefault();  
          if (containsPoint(ball.getBounds(), touch.x, touch.y)) {  
            console.log("in ball: touchstart");  
          } else {  
            console.log("canvas: touchstart");  
          }  
        }, false);  
      
        canvas.addEventListener('touchend', function (event) {  
          event.preventDefault();  
          console.log("canvas: touchend");  
        }, false);  
      
        canvas.addEventListener('touchmove', function (event) {  
          event.preventDefault();  
          if (containsPoint(ball.getBounds(), touch.x, touch.y)) {  
            console.log("in ball: touchmove");  
          } else {  
            console.log("canvas: touchmove");  
          }  
        }, false);  
      };  
      </script>  
     </body>  
    </html>
HTML5 Game - Touch events with ball movement

Description

Demo

Related Topics
