I have a text widget where I want to make enter event to behave like a tab event. so I capture the Key press event and raise a tab native event.
However the tab behavior is not reflected in the application. The code for event handler is
public void onKeyPress(KeyPressEvent event) {
int keyCode = event.getNativeEvent().getKeyCode();
if (keyCode == KeyCodes.KEY_ENTER) {
NativeEvent nativeEvent =
Document.get().
createKeyPressEvent(false,false,false,false,KeyCodes.KEY_TAB );
DomEvent.fireNativeEvent(nativeEvent, this, this.getElement());
}
When I use the deprecated createKeyPressEvent with more argument, it fires the tab event but the behavior is not as per the tab key press, which is to move to next widget. The new code changes from the above code in createKeyPress event line
as follows
NativeEvent nativeEvent =
Document.get().
createKeyPressEvent(false,false,false,false,
KeyCodes.KEY_TAB ,KeyCodes.KEY_TAB);
Note that manually firing an event
does not generate the default action
associated with that event. For
example, manually firing a focus event
does not cause the element to receive
focus (you must use its focus method
for that), manually firing a submit
event does not submit a form (use the
submit method), manually firing a key
event does not cause that letter to
appear in a focused text input, and
manually firing a click event on a
link does not cause the link to be
activated, etc. In the case of UI
events, this is important for security
reasons, as it prevents scripts from
simulating user actions that interact
with the browser itself.
From http://www.howtocreate.co.uk/tutorials/javascript/domevents.
Related
I'm currently working on a GWT project. I have a common block shared between multiple pages. I have some action buttons on that common block and the pages have a handler for the event launched on the click of those action buttons.
The problem I'm facing is that when I click on one of those action buttons on Page A, the handler from Page B previsouly registered would be called too.
So the solution I thought of was to remove the handler from a page when we leave it so there would be only one page at once with a registered handler to the same action button event.
First, I register to the action button click events and save the HandlerRegistration object returned from the addHandler method:
HandlerRegistration actionButtonClickEventHandlerRegistration=eventBus.addHandler(CommonBlockActionButtonClickedEvent.TYPE, someHandler);
And then, on page change event, I call removeHandler from the previously saved HandlerRegistration object
eventBus.addHandler(PageChangeEvent.TYPE, new PageChangeEventHandler() {
#Override
public void onMainPageChange(PageChangeEvent event) {
actionButtonClickEventHandlerRegistration.removeHandler();
}
});
So I do that on every pages, except that when I lauch my app and go to two of those pages, I get this error:
Caused by: java.lang.AssertionError: redundant remove call
Do you guys have any idea of why I'm getting this error or another way to solve my issue ?
Thanks a lot !
I would set the handler to null after removing it and I would check if it is actually null before removing it.
Like this:
eventBus.addHandler(PageChangeEvent.TYPE, new PageChangeEventHandler() {
#Override
public void onMainPageChange(PageChangeEvent event) {
if(actionButtonClickEventHandlerRegistration != null ) {
actionButtonClickEventHandlerRegistration.removeHandler();
actionButtonClickEventHandlerRegistration = null;
}
}
});
Nevertheless you seem to remove the handler at least twice and should check your program logic for that.
A good approach to do that is to set a breakpoint in the debugger (of your browser) on the line removing the handler. If you look at the call stack for every call to it, you should be able to spot the duplicate call and fix it.
I'm having an issue handling the forward button.
Basically, when a user is on a page and has made changes without saving then presses the backwards or forwards button they are presented with a prompt and two options: Leave or Stay.
I have implemented the backwards button fine, and choosing to stay on the page works well using History.newItem(currentToken) - the back button is still clickable.
However with the forwards button, if I use History.newItem(currentToken), it brings this to the front of the history stack and the forward button can no longer be clicked.
History.replaceItem(currentToken) causes the same issue.
How do I handle the cancelling of a forwards action so that I stay on my current page, but the forwards button is still enabled?
#Override
public void onValueChange(ValueChangeEvent<String> event) {
logger.info("back button pressed: " + event.getValue());
String evenVal = event.getValue();
String token = History.getToken();
AbstractPresenter presenter = sessionKiosk.getCurrentlyShowingPresenter();
if (presenter instanceof NSRCommonWorksheetPresenter && sessionKiosk.isDirty()) {
((NSRCommonWorksheetPresenter)presenter).setHistoryToken(event.getValue());
((NSRCommonWorksheetPresenter)presenter).showUnsavedChangesLeavingPageDialog();
}
else {
handleHistoryEvent(event.getValue());
}
}
The dialog is shown and when I click on stay on page the following is called.
public void stayOnCurrentPage() {
if (eventMap.get(prevPage) != null) {
History.newItem(prevPage, false);
}
}
Update: Basically history.newItem(value) removes the use of the forward button. Is there another way to cancel the event? If I just do nothing, th page stays where i want but the url still updates
None of the 3 options in the else statement seem to work.
Thanks.
You can simply cancel the event without touching History or tokens.
UPDATE:
It appears from your code that you are not intercepting the event (back/forward button), but let it go through, get the new token, and then force a return to the previous state under certain circumstances.
I suggest using Activities and Places pattern where every "place" within your app has a corresponding "activity". Each activity in your app will implement GWT Activity interface which includes mayStop() method. This method is called before a user navigates away from a specific place in your app, giving you an opportunity to warn a user and cancel the navigation if necessary.
In general, this pattern offers a very robust support for the History mechanism, covering many use cases.
If you want to support History mechanism yourself, take a look at PlaceChangeRequestEvent - it allows you to warn a user who tries to navigate away from a place in your app.
I have this situation, where I display a success/error message on a page and then I want it to disappear when the user does anything on the page (I assume that that triggers a click event, I can ignore events like going to new tab/windows etc.).
I have other "uihandlers" and "clickhandlers" on the page. So if I click empty regions on the page only the hidemessage call fires, else if I click valid 'clickable' elements my hidemessage fires first followed by the relevant handler.
Is there a way I can achieve this without adding hidemessage to all my clickhandlers on the page?
Edit: The message widget is not a PopupPanel, so setAutohide(true) won't work. But it is exactly the behavior I'm looking for. The widget is a custom widget which extends Composite implements HasWidget, HasClickHandlers
You can do this on your error message:
myPopupPanel.setAutoHideEnabled(true);
It does exactly whet you need. You may also consider setting auto-hide on history events (mostly back button):
myPopupPanel.setAutoHideOnHistoryEventsEnabled(true);
EDIT:
If you are not using a PopupPanel, you can make your Widget implement EventPreview, and then:
public boolean onEventPreview(Event event) {
Element target = DOM.eventGetTarget(event);
boolean widgetIsTarget = (target != null) && DOM.isOrHasChild(getElement(), target);
setVisible(widgetIsTarget):
I have a question regarding the event handling on client side in GWT.
In our application we have a quite complex structure of different modules and pages which are communicating via the gwt eventbus on client side. Now the amount of events is growing to fast for my opinion. E.g. I am opening a popup I need:
An event for opening the popup
An event for asking some data within the client
An event for getting back the data and fill in the dialog
An event for closing the popup
An event for handling the save Button
Am I thinking a little bit to complicated or missing something in the EventBus implementation? I just wanted to have some feedback out of the community as you are facing the same issues.
For what it's worth, I have lots of events and more growing. And yes, I wonder if I can do with less, but when I skip an event and link elements directly, I regret it.
Here's an example that I just fixed up yesterday. I have a DataGrid widget. I also support re-ordering of columns, hiding of columns, re-sizing columns, and coloring columns with a popup dialog. You click on a configure button, and a popup with the columns listed shows, and the user can click checkboxes to show or hide columns, click on a Move Up / Move Down button to re-order columns, and so on. Hit Apply on the popup and the popup disappears and the DataGrid re-configures.
Except that it didn't. You'd click on Apply and the popup would just sit there, the user would wonder what was going on, the DataGrid would re-configure underneath, and then the popup would go away. We're only talking a short amount of time -- maybe a second or a bit more -- but it was so so noticeable. Why was it happening? Because I got lazy and tied the popup directly to the configure button, and the Apply button directly to the DataGrid. You'd hit Apply, for example, and the call would be made to the DataGrid with the new configuration information. Only when the call returned would the popup would be torn down.
I knew it was bad when I did it, but I was being lazy. So I took the 20 minutes I needed to write up two messages and associated handlers in my mediator singleton. One message is issued by the DataGrid to start the configuration dialog, and one is issued by the popup to configure the DataGrid. Now the widgets are de-coupled, and the performance is much snappier. There is no sense of "stickiness".
Now to your example, can you not combine (1) and (2)? And also (3), (4), and (5)? When the user clicks the configure button on my app, the event carries with it the current configuration information (including a reference to the DataGrid that originated the request). You can call this information the "payload". When the user clicks the Apply button on the popup, the event payload includes all the new configuration information (including a reference to that original target DataGrid) that the event handler feeds to the target DataGrid when the event is handled. Two events -- one to kick off the configuration and one to apply the end result.
Yes there are a plethora of events in any app that does something interesting, but events can carry a lot of information, so I would look at whether your event organization is too fractured.
As a extra bit, here is the code I use. I shamelessly copied elements of this pattern from one of Google's examples.
The user can ask for help using a menu item:
#UiField
MenuItem help;
help.setCommand(new Command() {
#Override
public void execute() {
BagOfState.getInstance().getCommonEventBus().fireEvent(new MenuHelpEvent());
}
});
For the event (in this case, the event fired when the user clicks on the Help menu item):
public class MenuHelpEvent extends GwtEvent<MenuHelpEvent.Handler> {
private static final Type<Handler> TYPE = new Type<Handler>();
public interface Handler extends EventHandler {
void doMenuHelp();
}
#Override
public GwtEvent.Type<Handler> getAssociatedType() {
return TYPE;
}
#Override
protected void dispatch(Handler handler) {
handler.doMenuHelp();
}
public static HandlerRegistration register(EventBus eventBus, Handler handler) {
return eventBus.addHandler(TYPE, handler);
}
}
I have a singleton called Mediator in which ALL events are registered:
MenuHelpEvent.register(BagOfState.getInstance().getCommonEventBus(),
new MenuHelpEvent.Handler() {
#Override
public void doMenuHelp() {
new MenuHelp().execute();
}
});
Every event is mated with a Command object to do the work:
public class MenuHelp implements Command {
#Override
public void execute() {
new InfoMessage(BagOfState.APP_MSG.unimplementedFeatureCaption())
.setTextAndCenter(BagOfState.APP_MSG.unimplementedFeature());
}
}
Everything is decoupled. The menu widget is bound to a command that executes and then completes. The command fires the event on the bus then completes. The event fires off the execution of a Command and the completes. The Command shows the popup help panel (in this case, an "unimplemented" message to the user -- yeah, I'll get to it soon). Every interaction with a user's input is handled extremely quickly and resolves. It can kick off a series of events to perform a long action, but never tying up the GUI to do so. And of course, since the elements are decoupled, I can call the same elements in other places (for instance, call the help Command through a button push as well as a menu item).
In GXT, MessageBox methods are asynchronous, meaning that the application does not "lock up" while the message box is displayed.
I using a KeyListener to process enter key presses in a form (to increase usability, i.e., allowing the form to be submitted by the enter key) and subsequently disabling the form fields while the application processes the user's credentials. If they are incorrect, I show a MessageBox.alert() and then re-enable the form fields. However, since alert() returns immediately, the form fields are immediately made available again, allowing the user to input data without closing the alert.
The solution is to use a callback in alert(); however, the enter keypress not only causes the form to submit, but also causes the alert to immediately dismiss (as if both the form and the message box are processing the enter key). How do I keep the alert box open until the user presses enter a second time or clicks the "Ok" button?
The key is DeferredCommand provided by GWT:
This class allows you to execute code after all currently pending event handlers have completed, using the addCommand(Command) or addCommand(IncrementalCommand) methods. This is useful when you need to execute code outside of the context of the current stack.
if(!validate())
{
DeferredCommand.addCommand(new Command() {
public void execute() {
MessageBox.alert("Error", "You must enter a username and password.", alertListener);
return;
}
});
}