Handling custom events in GWT

[Christopher]

Hi there,

I've got a custom event fired by some JS code in an iframe. If I add
an event listener to the iframe via JS then the event is captured.
However I'm having difficulty capturing the same event within GWT;
indeed is it possible to capture custom events in GWT?

The event is constructed and fired in JS like so:

var event = document.createEvent("Event");
event.initEvent("hideWithMessage", true, true);
event.message = "This message to be reported.";

window.parent.document.getElementById("hatsPopup").dispatchEvent(event);

(executes within an iframe hence the window.parent.document business).

Here's how I attach my handler:

frame.addDomHandler(new HideWithMessageHandler() {
@Override
public void onHideWithMessage(String message) {
Window.alert("Yippee! " + message);
}

}, HideWithMessageEvent.getType());

The event is defined as:

public class HideWithMessageEvent extends
DomEvent<HideWithMessageHandler> {

private static final Type<HideWithMessageHandler> TYPE = new
Type<HideWithMessageHandler>(
"hideWithMessage", new HideWithMessageEvent());

public static Type<HideWithMessageHandler> getType() {
return TYPE;
}

@Override
public Type<HideWithMessageHandler> getAssociatedType() {
return TYPE;
}

@Override
protected void dispatch(HideWithMessageHandler handler) {
handler.onHideWithMessage(null);
}

}

...and the handler:

public interface HideWithMessageHandler extends EventHandler {
void onHideWithMessage(String message);
}

Incidentally if I try the same sort of thing using a clickEvent then
all is well i.e. I'm able to fire a click event at the iframe from JS
and capture it in GWT. The difficulty is with custom events.

Help and guidance very much appreciated.

Kind regards,
Christopher

[Jim Douglas]

Here's one way to support arbitrary events:

// iOS & Android touch events:

private final static String TOUCHSTART = "touchstart";
private final static String TOUCHMOVE = "touchmove";
private final static String TOUCHEND = "touchend";
private final static String TOUCHCANCEL = "touchcancel";
private final static int TOUCHTIMER = 550;
private Timer touchTimer = null;
private boolean cancelClickEvent = false;

private void addTouchListeners(Element element)
{
if (TouchHandler.supportsTouch())
{
sinkEvents(Event.ONCLICK);
addEventListener(element, TOUCHSTART, this, false);
addEventListener(element, TOUCHMOVE, this, false);
addEventListener(element, TOUCHEND, this, false);
addEventListener(element, TOUCHCANCEL, this, false);
}
}

private static native void addEventListener(Element element,
String event,
EventListener
listener,
boolean capture)
/*-{
element.addEventListener(
event,
function(e)
{

listener.@com.google.gwt.user.client.EventListener::onBrowserEvent(Lcom/
google/gwt/user/client/Event;)(e);
},
capture);
}-*/;

@Override
public void onBrowserEvent(Event event)
{
String type = event.getType();
if (TOUCHSTART.equals(type))
{
TouchEvent touchEvent = event.cast();
if (touchEvent.getTouches().length() == 1)
startTouchTimer(event);
else
cancelTouchTimer();
}
else if (TOUCHMOVE.equals(type))
{
cancelTouchTimer();
}
else if (TOUCHEND.equals(type))
{
cancelTouchTimer();
}
else if (TOUCHCANCEL.equals(type))
{
cancelTouchTimer();
}
else if ("click".equals(type))
{
if (cancelClickEvent)
{
event.preventDefault();
event.stopPropagation();
}
else
{
super.onBrowserEvent(event);

[Christopher]

Hi Jim,

You're doing what I was hoping to avoid - that is getting down to JSNI
and manipulating the DOM objects directly. I had hoped that I could
leverage the existing event architecture in GWT, but perhaps I can't.

Thanks anyhow.

Kind regards,
Christopher

[Thomas Broyer]

On Tuesday, March 1, 2011 11:24:06 PM UTC+1, Christopher wrote:

Hi Jim,

You're doing what I was hoping to avoid - that is getting down to JSNI
and manipulating the DOM objects directly. I had hoped that I could
leverage the existing event architecture in GWT, but perhaps I can't.

No, not currently (there's hope it will be "fixed" one day, but there are things with higher priority)