Hello,
I have a simple web app that consists of a circle moving around. When
I do a swipe, the app freezes and the circle stops moving, and I have
to do another swipe/tap to set it in motion again. This only happens
in Andoid 2.2 devices (2.3 works OK). Does anyone know why this
happens? How can I avoid this?
Here's the code:
<!doctype html>
<html>
<head>
<meta charset="UTF-8" />
<title>Canvas Test</title>
<script type="text/javascript" src="touch.js"></script>
</head>
<body>
<section>
<div>
<canvas id="canvas" width="400" height="300">
This text is displayed if your browser
does not support HTML5 Canvas.
</canvas>
<canvas id="canvas2" width="400" height="300">
This text is displayed if your browser
does not support HTML5 Canvas.
</canvas>
</div>
<script type="text/javascript">
var canvas;
var ctx;
var x = 400;
var y = 300;
var dx = 2;
var dy = 4;
var WIDTH = 400;
var HEIGHT = 300;
function circle(x,y,r) {
ctx.beginPath();
ctx.arc(x, y, r, 0, Math.PI*2, true);
ctx.fill();
}
function rect(x,y,w,h) {
ctx.beginPath();
ctx.rect(x,y,w,h);
ctx.closePath();
ctx.fill();
}
function clear() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
}
function init() {
document.getElementById('canvas').addEventListener('touchstart',
touchStart);
document.getElementById('canvas').addEventListener('touchmove',
touchMove);
document.getElementById('canvas').addEventListener('touchend',
touchEnd);
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
return setInterval(draw, 10);
}
function draw() {
clear();
ctx.fillStyle = "#FAF7F8";
rect(0,0,WIDTH,HEIGHT);
ctx.fillStyle = "#444444";
circle(x, y, 10);
if (x + dx > WIDTH || x + dx < 0)
dx = -dx;
if (y + dy > HEIGHT || y + dy < 0)
dy = -dy;
x += dx;
y += dy;
}
init();
</script>
</section>
</body>
</html>
<<--- touch.js --->>
var triggerElementID = null;
var fingerCount = 0;
var startXPosition = 0;
var startYPosition = 0;
var currentXPosition = 0;
var currentYPosition = 0;
var minLength = 72;
var swipeLength = 0;
var swipeDirection = null;
function touchStart(event,passedName) {
event.preventDefault();
fingerCount = event.touches.length;
if (fingerCount == 1 ) {
startXPosition = event.touches[0].pageX;
startYPosition = event.touches[0].pageY;
triggerElementID = passedName ? passedName : this.id;
} else {
touchCancel(event);
}
}
function touchMove(event) {
event.preventDefault();
if (event.touches.length == 1 ) {
currentXPosition = event.touches[0].pageX;
currentYPosition = event.touches[0].pageY;
} else {
touchCancel(event);
}
}
function touchEnd(event) {
try {
event.preventDefault();
if ( fingerCount == 1 && currentXPosition != 0 ) {
currentXPosition = event.touches[0].pageX;
currentYPosition = event.touches[0].pageY;
swipeLength =
Math.round(Math.sqrt(Math.pow(currentXPosition -
startXPosition,2) + Math.pow(currentYPosition - startYPosition,2)));
if ( swipeLength >= minLength ) {
caluculateAngle();
}
}
} finally {
touchCancel(event);
}
}
function touchCancel(event) {
fingerCount = 0;
startXPosition = 0;
startYPosition = 0;
currentXPosition = 0;
currentYPosition = 0;
swipeLength = 0;
swipeDirection = null;
triggerElementID = null;
}
Thanks!
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