Re: visibilitychange event
Ah, yes, good pickup, thanks. Final, final code: :-)
import com.google.gwt.user.client.Command;
private static native final String getVisibilityState()/*-{
return $doc.visibilityState;
}-*/;
private static native final void listenForVisibilityChange(Command onChange)
/*-{
$doc.addEventListener("visibilitychange", $entry(function() {
onchan...@com.google.gwt.user.client.Command::execute(*)();
}), false);
}-*/;
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Re: visibilitychange event
You're misusing $entry(): it takes a function as argument and returns a
function; it should be used to wrap the function(){}.
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Re: visibilitychange event
Thanks Thomas. Final code for reference:
import com.google.gwt.user.client.Command;
private static native final String getVisibilityState() /*-{
return $doc.visibilityState;
}-*/;
private static native final void listenForVisibilityChange(Command onChange)
/*-{
$doc.addEventListener("visibilitychange", function() {
$entry(onchan...@com.google.gwt.user.client.Command::execute(*)());
}, false);
}-*/;
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Re: visibilitychange event
Thanks Thomas. Final code for reference:
import com.google.gwt.user.client.Command;
private static native final String getVisibilityState() /*-{
return $doc.visibilityState;
}-*/;
private static native final void listenForVisibilityChange(Command onChange)
/*-{
$doc.addEventListener("visibilitychange", $entry(function() {
onchan...@com.google.gwt.user.client.Command::execute(*)();
}), false);
}-*/;
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Re: visibilitychange event
Thanks Jens. Now switched it to use *$doc*. And, yes, I just register
once, and fire a custom event on the event bus. Although, I just did it
using my own event bus like this:
final EventBus EVENT_BUS = GWT.create(SimpleEventBus.class);
listenForVisibilityChange(new Command() {
@Override
public void execute() {
boolean visible = "visible".equals(getVisibilityState());
EVENT_BUS.fireEvent(new WindowVisibilityChangedEvent(visible));
}
});
I suspect your way is better, although, I don't really understand what
sinking events onto the DOM is doing.
elemental2 looks cool! Will check it out.
My custom event if anyone wants to reuse it:
public class WindowVisibilityChangedEvent extends GwtEvent<
WindowVisibilityChangedEventHandler> {
public static Type TYPE = new Type<
WindowVisibilityChangedEventHandler>();
private boolean visibile;
public WindowVisibilityChangedEvent(boolean visible) {
this.visibile = visible;
}
@Override
public Type getAssociatedType() {
return TYPE;
}
@Override
protected void dispatch(WindowVisibilityChangedEventHandler handler) {
handler.visibilityChanged(this);
}
public boolean isVisibile() {
return visibile;
}
}
And the handler:
public interface WindowVisibilityChangedEventHandler extends EventHandler {
void visibilityChanged(WindowVisibilityChangedEvent
windowVisibilityChangedEvent);
}
Cheers.
On Monday, August 7, 2017 at 7:21:33 PM UTC+10, Jens wrote:
>
> Generally ok, given it is a global listener and you probably just install
> it once on app initialization. However you should use *$doc* instead of
> *document* to make sure you listen on the global document. Depending on
> your browser support you might want a utility method to check if visibility
> change events are actually supported by the browser.
>
> static native boolean isSupported() /*-{
> return $doc.hidden !== 'undefined' && $doc.visibilityState !==
> 'undefined';
> }-*/;
>
> In our app we created a PageVisibilityChangedEvent which extends GwtEvent
> and then fire it on the app wide EventBus so everyone can easily listen
> for it. To register the DOM handler we used
>
> Element doc = Document.get().cast();
> DOM.sinkBitlessEvent(doc, VISIBILITY_CHANGE_EVENT);
> DOM.setEventListener(doc, new EventListener() {
> @Override
> public void onBrowserEvent(final Event event) {
> if (VISIBILITY_CHANGE_EVENT.equals(event.getType())) {
> firePageVisibilityChangedEvent();
>}
> }
> });
>
> You could of course also use elemental2 (requires newest GWT) or JsInterop
> to reduce the amount of JSNI if that is important for you.
>
> -- J.
>
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Re: visibilitychange event
Generally ok, given it is a global listener and you probably just install
it once on app initialization. However you should use *$doc* instead of
*document* to make sure you listen on the global document. Depending on
your browser support you might want a utility method to check if visibility
change events are actually supported by the browser.
static native boolean isSupported() /*-{
return $doc.hidden !== 'undefined' && $doc.visibilityState !==
'undefined';
}-*/;
In our app we created a PageVisibilityChangedEvent which extends GwtEvent
and then fire it on the app wide EventBus so everyone can easily listen for
it. To register the DOM handler we used
Element doc = Document.get().cast();
DOM.sinkBitlessEvent(doc, VISIBILITY_CHANGE_EVENT);
DOM.setEventListener(doc, new EventListener() {
@Override
public void onBrowserEvent(final Event event) {
if (VISIBILITY_CHANGE_EVENT.equals(event.getType())) {
firePageVisibilityChangedEvent();
}
}
});
You could of course also use elemental2 (requires newest GWT) or JsInterop
to reduce the amount of JSNI if that is important for you.
-- J.
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