Convert to touch events

[jumbee]

Hi

I'm learning javascript and trying to put it also on mobile (android). How can I translate this function on touch events? Thank you

//Draw circle
function drawCircle(e) {

	var canvasOffset = canvas.offset();
	var canvasX = Math.floor(e.pageX-canvasOffset.left);
	var canvasY = Math.floor(e.pageY-canvasOffset.top);

	
	cb_ctx.beginPath();
 	cb_ctx.arc(canvasX,canvasY,cb_ctx.lineWidth/2,0,Math.PI*2,true);
 	cb_ctx.fillStyle = cb_ctx.strokeStyle;
 	cb_ctx.fill();

}

[Logic Ali]

The code that you posted is irrelevant to the question.
What current event handlers do you want to duplicate?

[jumbee]

I've got these event handlers and would like to use the mentioned function on touchdown.

	cb_canvas = document.getElementById("cbook");

	cb_lastPoints = Array();

	if (cb_canvas.getContext) {
		cb_ctx = cb_canvas.getContext('2d');
		cb_ctx.lineWidth = 14;
		cb_ctx.strokeStyle = "#0052f8";
		cb_ctx.lineJoin="round";
		cb_ctx.lineCap="round"
		cb_ctx.beginPath();

		cb_canvas.onmousedown = startDraw;
		cb_canvas.onmouseup = stopDraw;
		cb_canvas.ontouchstart = startDraw;
		cb_canvas.ontouchstop = stopDraw;
		cb_canvas.ontouchmove = drawMouse;
	}

[Logic Ali]

		cb_canvas.ontouchstop = stopDraw;

That should be ontouchend. Are you saying the other touch handlers aren't working?

[jumbee]

hi

all the others are working just fine. also this drawCircle function works fine, but just in a browser. As soon as I export it to my android phone, it stops.

[jumbee]

I forgot to add also this. I call this drawCirle function here:

function stopDraw(e) {
	drawCircle(e);
	e.preventDefault();
	cb_canvas.onmousemove = null;
}

and as I have said, it works fine in a browser, but it doesn't work on the phone.

[Logic Ali]

I forgot to add also this. I call this drawCirle function here:

function stopDraw(e) {
	drawCircle(e);
	e.preventDefault();
	cb_canvas.onmousemove = null;
}

and as I have said, it works fine in a browser, but it doesn't work on the phone.

Did you rename the event handler to ontouchend ?

Have you determined whether or not stopDraw is being called?

[jumbee]

StopDraw is being called. I have put on the beginning of the drawCircle function an alert and as I have touched and moved my finger it showed up. I can send you the complete code so you can see

[Logic Ali]

StopDraw is being called. I have put on the beginning of the drawCircle function an alert and as I have touched and moved my finger it showed up.

From the code you showed, I would expect StopDraw to be called when you lift off.

[jumbee]

yes it is true. bellow I have pasted the complete code...

	cb_canvas = document.getElementById("cbook");

	cb_lastPoints = Array();

	if (cb_canvas.getContext) {
		cb_ctx = cb_canvas.getContext('2d');
		cb_ctx.lineWidth = 14;
		cb_ctx.strokeStyle = "#0052f8";
		cb_ctx.lineJoin="round";
		cb_ctx.lineCap="round"
		cb_ctx.beginPath();

		cb_canvas.onmousedown = startDraw;
		cb_canvas.onmouseup = stopDraw;
		cb_canvas.ontouchstart = startDraw;
		cb_canvas.ontouchstop = stopDraw;
		cb_canvas.ontouchmove = drawMouse;
	}



	
	
function startDraw(e) {
	if (e.touches) {
		// Touch event
		for (var i = 1; i <= e.touches.length; i++) {
			cb_lastPoints[i] = getCoords(e.touches[i - 1]); // Get info for finger #1
		}
	}
	else {
		// Mouse event
		cb_lastPoints[0] = getCoords(e);
		cb_canvas.onmousemove = drawMouse;
	}
	
	return false;
}

// Called whenever cursor position changes after drawing has started
function stopDraw(e) {
	drawCircle(e);
	e.preventDefault();
	cb_canvas.onmousemove = null;
}

//Draw circle
function drawCircle(e) {
    var canvasOffset = canvas.offset();
	var touch = event.touches;
//	var canvasX = Math.floor(e.pageX-canvasOffset.left);
//	var canvasY = Math.floor(e.pageY-canvasOffset.top);
	var canvasX = touch.pageX;
	var canvasY = touch.pageY;

	
	cb_ctx.beginPath();
 	cb_ctx.arc(canvasX,canvasY,cb_ctx.lineWidth/2,0,Math.PI*2,true);
 	cb_ctx.fillStyle = cb_ctx.strokeStyle;
 	cb_ctx.fill();

}


function drawMouse(e) {
	cb_ctx.beginPath();
	if (e.touches) {
		// Touch Enabled
		for (var i = 1; i <= e.touches.length; i++) {
			var p = getCoords(e.touches[i - 1]); // Get info for finger i
			cb_lastPoints[i] = drawLine(cb_lastPoints[i].x, cb_lastPoints[i].y, p.x, p.y);
		}
	}
	else {
		// Not touch enabled
		var p = getCoords(e);
		cb_lastPoints[0] = drawLine(cb_lastPoints[0].x, cb_lastPoints[0].y, p.x, p.y);
	}
	cb_ctx.stroke();
	cb_ctx.closePath();
	//cb_ctx.beginPath();

	return false;
}

// Draw a line on the canvas from (s)tart to (e)nd
function drawLine(sX, sY, eX, eY) {
	cb_ctx.moveTo(sX, sY);
	cb_ctx.lineTo(eX, eY);
	return { x: eX, y: eY };
}

// Get the coordinates for a mouse or touch event
function getCoords(e) {
	if (e.offsetX) {
		return { x: e.offsetX, y: e.offsetY };
	}
	else if (e.layerX) {
		return { x: e.layerX, y: e.layerY };
	}
	else {
		return { x: e.pageX - cb_canvas.offsetLeft, y: e.pageY - cb_canvas.offsetTop };
	}
}

[Logic Ali]

	cb_canvas.ontouchstop = stopDraw;

For the third time: That needs to be ontouchend

I'm done with this thread.

[jumbee]

oh, sooooorry. i was not reading it well. your suggestion helps a bit, but now a funny thing happened. circle is drawn in the top left corner. center coordinates are 0,0. strange...