I want to handle the event in the case of link by my own event listener.If we click on a link in browser, browser will open the address given in the link but i want to call my own event listener. I tried to do it in GWT by removing the attribute of the anchor tag which worked but it is not a clean solution.
So if you are having any idea how to block the browser from opening that link please reply.
In GWT 1.6 the correct code is:
ClickHandler foo = new ClickHandler() {
public void onClick(ClickEvent event) {
/// do your stuff
event.stopPropagation(); // stops the event from bubbling to parent
event.preventDefault(); // prevents the browsers default action,
// following a link, etc
}
}
This is roughly equivalent to:
Link
Isn't that what this widget does:
http://google-web-toolkit.googlecode.com/svn/javadoc/1.6/com/google/gwt/user/client/ui/Hyperlink.html
eg: it looks like a normal hyperlink but lets you handle the onclick event?
You can just call event.cancel() (GWT 1.6) or
Event.getCurrentEvent().cancelBubble(true); // In 1.4 and earlier
DOM.eventCancelBubble(DOM.eventGetCurrentEvent(), true); // In 1.5
There is also a method to cancel an event from its instance within GWT 1.5, but I can't remember.
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 am trying to open an email client just like using mail me tag.
But I want to use my custom widget, which is not hyperlink, anchor or so. I added a DOM handler to my widget to listen to clicks:
public class VContactWidget extends VHorizontalLayout implements ClickHandler {
private HandlerRegistration clickHandler;
public VContactWidget() {
// added some content here
clickHandler = addDomHandler(this, ClickEvent.getType());
}
#Override
public void onClick(ClickEvent event) {
Window.open("mailto:john.doe#mail.com", "_blank", "");
}
}
Everything is working fine except one detail: When the widget is clicked, new empty browser tab will open with url set to mailto:john.doe#mail.com. I don't want the new tab opened. Can I avoid it somehow?
Note I set _blank parameter, as used in many examples. I also tried to use empty string or some other values as well. I looked into documentation, but didn't find anything useful.
https://developer.mozilla.org/en-US/docs/Web/API/window.open
One solution may be to use Anchor, but my component is more complex, not just single <a> link.
Another detail to note may be application server - I am using Tomcat 7 now.
Trying to fire native event on hidden Anchor programatically did not work for me. (Which does not mean it cannot be done.)
This is, how I actually solved my problem: Instead of Window.open(), I used following call:
public void onClick(ClickEvent event) {
Window.Location.assign("mailto:john.doe#mail.com");
}
This is not something that you can control. Whether this link opens in a new tab or a new window depends on the browser settings and user preferences.
I don't think it will make a difference if you use an Anchor or Window.open. In either case, the behavior may be different in different browsers. Also remember that for some users a click on this link will open Outlook or Mail, while for other users it will open Gmail in a browser window.
UPDATE:
If you want an exact behavior of an <a> element, create a hidden anchor element and fire a click on it when a user clicks on your composite widget.
Firing click event from code in gwt
As we are facing GWT performance issues in a mobile app I peeked into Google Wave code since it is developed with GWT.
I thought that all the buttons there are widgets but if you look into generated HTML with firebug you see no onclick attribute set on clickable divs. I wonder how they achieve it having an element that issues click or mousedown events and seemingly neither being a widget nor injected with onclick attribute.
Being able to create such components would surely take me one step further to optimizing performance.
Thanks.
ps: wasnt google going to open source client code too. Have not been able to find it.
You don't have to put an onclick attribute on the HTML to make it have an onclick handler. This is a very simple example:
<div id="mydiv">Regular old div</div>
Then in script:
document.getElementById('mydiv').onclick = function() {
alert('hello!');
}
They wouldn't set the onclick property directly, it would have been set in the GWT code or via another Javascript library.
The GWT documentation shows how to create handlers within a GWT Java app:
public void anonClickHandlerExample() {
Button b = new Button("Click Me");
b.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
// handle the click event
}
});
}
This will generate an HTML element and bind a click handler to it. However, in practice this has the same result as using document.getElementById('element').onclick() on an existing element in your page.
You can hook functions to the onclick event using JavaScript. Here's an example using jQuery:
$(document).ready(function(){
$("#div-id").click(function(){
/* Do something */
});
});
If you're interested in optimizing performance around this, you may need to investigate event delegation, depending on your situation.
A click event is generated for every DOM element within the Body. The event travels from the Body down to the element clicked (unless you are using Internet Explorer), hits the element clicked, and then bubbles back up. The event can be captured either through DOM element attributes, event handlers in the javascript, or attributes at any of the parent levels (the bubbling or capturing event triggers this).
I'd imagine they've just set it in a .js file.
Easily done with say jQuery with $(document).ready() for example.
how to load the other HTML page when i click a button? i'm using GWT 2.0.3.
p.addClickHandler(new ClickHandler() {
public void onClick(ClickEvent event) {
// TODO Auto-generated method stub
// is there a syntax to load other HTML?
}
});
thanks before, Rafael.
If you use GWT's history mechanism, then you want to look at History.newItem("newPage");
If you want to jump to a totally new URL (and navigate outside your application) then you can use Window.Location.replace("newURL");.
Finally, if you just want to change the page within your application but are not using history, then you probably want to do something like:
RootPanel.get().clear()
RootPanel.get().add( widgetForNewPage );
I would like to trigger a click on the browse button on a hidden FileUpload widget.
The following code works fine on IE 6+, but doesn't work in FireFox.
final FileUpload upload = new FileUpload();
upload.setVisible(false);
upload.setName("uploadFormElement");
panel.add(upload);
panel.add( new Button("Select File", new ClickListener()
{ public void onClick(Widget pSender)
{ jsClickUpload( upload.getElement() ); } }));
native void jsClickUpload( Element pElement ) /*-{ pElement.click(); }-*/;
How can I achieve the same in FireFox (and possibly other browsers)?
The solution can be read here:
http://www.quirksmode.org/dom/inputfile.html
in the last paragraph:
The click() method allows you to
simulate a click on a form field.
Checkboxes get toggled, radios
selected, and so on. Unfortunately
Mozilla and Opera haven't added this
method to file upload fields. I wonder
why, adding it is not really a
security risk since the worst that can
happen is that the file selection
window pops up.
have you tried calling the onClick() method directly?
The click method is currently in the process of being implemented in FF 4. It is being discussed what security rules will be implemented and it sounds like it will be similar to Window.open and must be the direct result of a user action and not a timer or load.