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How to wire up GWT hyperlink click handler?

I am brand new to GWT and am trying to achieve the following:
Here's the code that I've cooked up:
public class MyWebApp implements EntryPoint {
// The main container for everything the user sees (the "view")
private LayoutPanel mainPanel;
// Simple HTML for the header ("MyWebApp") and subsequent <hr/>
private SafeHtml header;
// The three links "Dashboard", "Monitors" and "Help Desk"
private HorizontalPanel navMenu;
// The empty content that gets populated when user clicks one of
// the 3 links.
private Panel menuContent;
#Override
public void onModuleLoad() {
// The initial fragment contains the header, nav menu and empty "content" div.
// Each menu/screen then fills out content div.
initMainPanel();
RootPanel.get().add(mainPanel);
}
private void initMainPanel() {
SafeHtmlBuilder headerBuilder = new SafeHtmlBuilder();
navMenu = new HorizontalPanel();
// Leaving null until user clicks on one of the 3 menus.
// Then the menu will decide what panel gets injected for
// this panel.
menuContent = null;
// Create the simple HTML for the header.
headerBuilder.append("<h1>MyWebApp</h1><hr/>");
// Create the navMenu items.
Hyperlink dashboardLink, monitorsLink, helpDeskLink;
// Homepage is http://www.mywebapp.com
// I want the dashboardLink to inject menuContent and "redirect" user to
// http://www.mywebapp.com/dashboard
dashboardLink = new Hyperlink("???", "???");
// http://www.mywebapp.com/monitors
monitorsLink = new Hyperlink("???", "???");
// http://www.mywebapp.com/help-desk
helpDeskLink = new Hyperlink("???", "???");
navMenu.add(dashboardLink);
navMenu.add(monitorsLink);
navMenu.add(helpDeskLink);
// Add all widgets to the mainPanel.
mainPanel.add(new HTML(headerBuilder.toSafeHtml().toString()));
mainPanel.add(navMenu);
mainPanel.add(menuContent);
// Position and size the widgets (omitted for brevity).
// mainPanel.setWidgetHorizontalPosition(...);
}
private HTML getDashboardMenuContent() {
return new HTML("This is the dashboard.");
}
private HTML getMonitorsMenuContent() {
return new HTML("These are the monitors.");
}
private HTML getHelpDeskMenuContent() {
return new HTML("This is the help desk.");
}
}
Most importantly:
How do I "wire up" the Hyperlinks so that when the user clicks them, I can call the appropriate getXXXMenuContent() method, and then add that to menuContent?
But also:
I feel like I'm doing something wrong here: mainPanel.add(new HTML(headerBuilder.toSafeHtml().toString())); - if so what is it?!? How should I be adding a simple <h1> and <hr/> in a way that's secure (hence the use of the Safe* objects), efficient, and conforming to recommended practices?
Should I be implementing UiBinder here? If so, would I make UiBinders for each menu's content or for the entire mainPanel, or both?
Thanks in advance!

Hyperlink widgets trigger navigation. You don't want to handle clicks on them, you want to handle navigation (that could be triggered by clicking a Hyperlink or using the browser's back/forward buttons, a bookmark or link from elsewhere –including Ctrl+clicking a Hyperlink to open it in a new window/tab–, etc.)
To react to those navigation events, use History.addValueChangeHandler; and to handle the initial navigation on application start, call History.fireCurrentHistoryState() (after you add your handler of course).
More details in: https://developers.google.com/web-toolkit/doc/latest/DevGuideCodingBasicsHistory
Would be better to split other questions to... other questions, but here are the answers anyway:
I feel like I'm doing something wrong here: mainPanel.add(new HTML(headerBuilder.toSafeHtml().toString())); - if so what is it?!? How should I be adding a simple <h1> and <hr/> in a way that's secure (hence the use of the Safe* objects), efficient, and conforming to recommended practices?
The HTML widget has a constructor taking a SafeHtml so you don't need to call toString().
If you're only using a constant, you don't need a SafeHtmlBuilder; use SafeHtmlUtils instead. But constants are no more or less secure with or without SafeHtml, SafeHtml just makes it easier to find all occurrences of HTML in your code, to help in doing a security review of your app (BTW, we're doing HTML, so <hr>, not <hr/>; if you really want it to look like XML/XHTML, then use <hr /> but you're only cheating yourself here)
Should I be implementing UiBinder here? If so, would I make UiBinders for each menu's content or for the entire mainPanel, or both?
If you don't feel the need for UiBinder, you don't have to use it. But in this case it won't change anything: you're not handling widget events, but history events.

Something like
dashboardLink.addClickHandler(
new ClickHandler()
{
public void onClick( ClickEvent event )
{
mainPanel.setWidget( getDashboardMenuContent() );
}
} );
You should note that Hyperlink.addClickHandler(...) is deprecated and it is recommended to use Anchor.addClickHandler(...) instead.
As for the other questions: It is a lot more elegant and easier to build UI's with UIBinder, so definitely look into that, but do try to make "it" work first to avoid the added complexity of the .ui.xml setup :-)
Cheers,

I have one simple piece of advice to give you. Use what the framework has to offer.
The HTML widget should be your last escape. There are so many widgets that there is no need for you to write html almost anywhere in your code.
So instead of headerBuilder, you can user the following piece of code
Label header = new Label("MyWebApp");
header.setStyleName("headerStyle",true);
You can set the style properties in an external Css file and add the reference inside the base html file or the gwt.xml file. So that answers your question about mainPanel.add(new HTML(headerBuilder.toSafeHtml().toString()));
In respect to the Hyperlink. If you choose to use hyperlinks, remember that the most effective usage is with the MVP pattern better known as Places and Activities (Lots of information on the web)
If you want something simpler instead the MenuBar and MenuItem classes should do the trick.
Look here for an example on how to use the MenuBar to control your application. There are many other ways but why not use the tools provided?
Also the UIBinder Vs the Designer/Classes methods is extensively discussed on stackoverflow resulting to a matter of choice and programming familiarity/preference.

How to both start a file download and close a (jQuery) dialog in Wicket?

In a Wicket app, I have a modal dialog that contains a simple form and a button. User enters values (report parameters), and then clicks the button which starts the download of a report file (typically a PDF). (All form values are required, and Wicket's validation mechanism is used to make sure user entered them before the download can start.)
Maybe this is better explained with a picture:
I'm using here a jQuery UI Dialog (instead of Wicket's ModalWindow which felt a lot clumsier and uglier from user's perspective).
Everything is pretty much working, except closing the dialog when/after clicking the download button.
Current version (irrelevant bits omitted):
public class ReportDownloadLink extends Link {
public ReportDownloadLink(String id, ReportDto report) {
super(id);
this.report = report;
}
#Override
public void onClick() {
IResourceStream resourceStream = new AbstractResourceStreamWriter() {
#Override
public void write(OutputStream output) {
try {
reportService.generateReport(output, report);
} catch (ReportGenerationException e) {
// ...
}
}
#Override
public String getContentType() {
// ...
}
};
ResourceStreamRequestTarget target =
new ResourceStreamRequestTarget(resourceStream, report.getFileName());
getRequestCycle().setRequestTarget(target);
}
The dialog is a Wicket Panel (which makes use of ReportDownloadLink above), which we put in a certain div, and then when a report is selected in a list, the dialog is opened from an AjaxLink's onClick() quite simply like this:
target.appendJavascript(String.format("showReportExportDialog('%s')", ... ));
Which calls this JS function:
function showReportExportDialog(dialogTitle) {
$("#reportExportPanelContainer").dialog(
{modal:true, draggable:true, width: 320, height: 330, title: dialogTitle}
);
}
Some options:
Make ReportDownloadLink extend something else than Link, perhaps, and/or find an appropriate method to override which would allow me to execute the tiny bit of JavaScript needed to close the jQuery Dialog.
Investigate jQuery + Wicket libraries (such as jqwicket or wiquery) that supposedly make these two work better together.
Latest thing I tried was overriding method getOnClickScript() in ReportDownloadLink which seemed promising (according to the Javadocs, it returns "Any onClick JavaScript that should be used"):
#Override
protected CharSequence getOnClickScript(CharSequence url) {
return "closeDownloadDialog()";
}
Thing is, this causes onClick() not to be called at all, i.e., the download doesn't start.
Could I perhaps override some more "ajaxy" class from Wicket (than Link) to combine these things: first init the download, then call the JS for closing the dialog?
Any recommendations or experiences from similar cases? Note that I want to keep using the jQuery dialog here, even though it makes things like these more complicated. Using a DownloadLink (see related question) is fine too in case that makes things easier.
NB: if you recommend JQWicket or wiQuery, please provide an example of how to do this.

Maybe you can try to bind the close modal code to the button "click" event using only JQuery, in your modal panel page, add something similar to ${"#mySubmit").click(myCloseModalFunction). It should keep Wicket default's behavior and add modal closing in the mix.
The other way is to override the getOnClickScript(...) method but the javascript has to return true in order for the browser to call the continue link evaluation and load the corresponding href. If you return false, the evaluation stops. I would suggest something like
#Override
protected CharSequence getOnClickScript(CharSequence url) {
return "closeDownloadDialog();return true;";
}
Hope it helps...

See https://cwiki.apache.org/WICKET/ajax-update-and-file-download-in-one-blow.html for inspiration.

How to use GWT fileupload?

I have some queries when trying to implement a fileupload widget in my application. After many tries, it just doesn't seem to work.
Hence, I tried getting working solutions to see if I can understand anything from there.
http://code.google.com/p/faculty-gwt/source/checkout
However, I tried uploading a file using this and it seems that I am getting error messages too. and what is that textbox and listbox suppose to do? It is meant for showing an example of validating an input before submitting?
Can someone guide me along to solve this? Thanks.

Never tried to use the link you provided, but this is what i did to use a a GWT FileUpload widget:
I built a File Upload widget using the uibinder:
<g:FormPanel ui:field="docForm">
<g:FlowPanel ui:field="inputPane">
/*other displayed info*/
<g:FileUpload ui:field="DocPath"/>
/*other displayed info*/
</g:FlowPanel>
</g:FormPanel>
(Per the GWT api, FileUpload widgets can only be used from a FormPanel)
Make sure you set these in the FormPanel, otherwise you'll probably have issues:
yourFormPanel.setEncoding(FormPanel.ENCODING_MULTIPART);
yourFormPanel.setMethod(FormPanel.METHOD_POST);
That widget is dropped into my container page, then added to the display panel:
private FileUploadWidget createNewUploader(){
FileUploadWidget uploader = new FileUploadWidget(/*my constructor params*/);
uploader.addChangeHandler(new ChangeHandler() {
#Override
public void onChange(ChangeEvent event) {
DocPanel.add(createNewUploader());
}
});
return uploader;
}
My OnChange event is so that I have a new, blank uploader available when i use the current one.
and when I'm ready to submit:
private void processUpload(FileUploadWidget upload, int id) {
upload.setId(id);
//Don't bother to submit an empty one.
if (upload.IsFileSelected())
upload.Submit();
}

Bridge between the Java applet and the text input controls on the web page

I have been working with a Java applet which is an applet that helps to write using only a mouse. For my case, I am trying to incorporate this into my webiste project as follows:
When the user clicks on any input element (textbox/textarea) on the page, this JAVA applet loads on the webpage itself. In the screenshot of the JAVA applet seen below, the user points to an alphabet to and the corresponding text gets written in the text box of the applet.
Now what I am trying to do is to get this text from the TextBox of the applet to the input element on the webpage. I know that this needs an interaction between the Java and JavaScript, but not being a pro, I really do not have the catch. Here's the Java applet and the code I have written.
Java applet and jQuery code (298kB): http://bit.ly/jItN9m
Please could somebdoy help for extending this code.
Thanks a lot!
Update
I searched somewhere and found this -> To get the text inside of Java text box, a getter method in the Applet to retrieve the text:
public class MyApplet extends JApplet {
// ...
public String getTextBoxText() { return myTextBox.getText(); }
}
In the JQuery code, the following lines are to be added I think:
var textBoxText = $("#applet-id")[0].getTextBoxText();
//Now do something with the text
For the code of the applet, I saw a GNOME git page here. The getText call already exists -- look at the bottom of this file: http://git.gnome.org/browse/dasher/tree/java/dasher/applet/JDasherApplet.java
I'd need to call 'getCurrentEditBoxText' but when should this method 'getCurrentEditBoxText' be called?
In my case, I would probably have to do it when the user clicks in a new input control etc.

You can have full communication between your Applet and any javascript method on the page. Kyle has a good post demonstrating how the Javascript can call the applet and request the text value. However, I presume you want the HTML Textfield to update with each mouse click, meaning the applet needs to communicate with the page. I would modify your javascript to something like this:
var activeTextArea = null;
$('textarea, input').click(function() {
$(this).dasher();
activeTextArea = this;
});
function updateText(text) {
// Careful: I think textarea and input have different
// methods for setting the value. Check the
// jQuery documentation
$(activeTextArea).val(text);
}
Assuming you have the source for the applet, you can have it communicate with the above javascript function. Add this import:
import netscape.javascript.JSObject;
And then, in whatever onClick handler you have for the mouse clicks, add:
// After the Applet Text has been updated
JSObject win = null;
try {
win = (JSObject) JSObject.getWindow(Applet.this);
win.call("updateText", new Object[] { textBox.getText() });
} catch (Exception ex) {
// oops
}
That will update the text each time that chunk of code is called. If you do NOT have access to the applet source, things get trickier. You'd need to set some manner of javascript timeout that constantly reads the value from the applet, but this assumes the applet has such a method that returns the value of the textbox.
See Also: http://java.sun.com/products/plugin/1.3/docs/jsobject.html
Update Modifying the applet is your best shot since that is where any event would be triggered. For example, if you want the HTML TextField to change on every click, the click happens in the applet which would need to be modified to trigger the update, as described above. Without modifying the applet, I see two options. Option #1 uses a timer:
var timer;
var activeTextArea;
$('textarea, input').click(function() {
$(this).dasher();
activeTextArea = this;
updateText();
}
function updateText() {
// Same warnings about textarea vs. input
$(activeTextArea).val($('#appletId')[0].getCurrentEditBoxText());
timer = setTimeout("updateText()", 50);
}
function stopUpdating() {
clearTimeout(timer);
}
This is similar to the code above except clicking on a text area triggers the looping function updateText() which will set the value of the HTML text field to the value of the Applet text field every 50ms. This will potentially introduce a minor delay between click and update, but it'll be small. You can increase the timer frequency, but that will add a performance drain. I don't see where you've 'hidden' the applet, but that same function should call stopUpdating so that we are no longer trying to contact a hidden applet.
Option #2 (not coded)
I would be to try and capture the click in the Applet as it bubbles through the HTML Dom. Then, you could skip the timer and put a click() behavior on the Applet container to do the same update. I'm not sure if such events bubble, though, so not sure if this would work. Even if it did, I'm not sure how compatible it would be across browsers.
Option #3
Third option is to not update the HTML text field on every click. This would simply be a combination of Kyle's and my posts above to set the value of the text field whenever you 'finish' with the applet.

Here's a possible solution. To get the text inside of your Java text box, write a getter method in the Applet to retrieve the text:
public class MyApplet extends JApplet {
// ...
public String getTextBoxText() { return myTextBox.getText(); }
}
In your JQuery code, add the following lines:
var textBoxText = $("#applet-id")[0].getTextBoxText();
//Now do something with the text
I found most of what I posted above here. Hope this helps.

This page explains how to manipulate DOM from a Java applet. To find the input element, simply call the document.getElementById(id) function with id of an id attribute of the text input box.

Wicket ListView not refreshing

I am taking my first steps with Apache Wicket and ran into the following problem. I have a ListView that displays a "delete" link right next to its entries. When the delete link is clicked, the entity represented by the list item is deleted from the database but the list itself does not get updated until I reload the page manually in the browser.
IModel<List<SampleEntity>> sampleEntityListModel = new LoadableDetachableModel<List<SampleEntity>>() {
#Override
protected List<SampleEntity> load() {
return mSampleEntityBA.findAll();
}
};
mListview = new ListView<SampleEntity>("listview", sampleEntityListModel) {
#Override
protected void populateItem(final ListItem<SampleEntity> item) {
item.add(new Label("listlabel", new PropertyModel<String>(item.getModelObject(),
"text")));
item.add(new Link<SampleEntity>("deleteLink", item.getModel()) {
#Override
public void onClick() {
mSampleEntityBA.delete(item.getModelObject());
}
});
}
};

When onClick called, item.getModelObject() pulls from the sampleEntityListModel which in turn calls mSampleEntityBA.findAll(). The model object of sampleEntityListModel will be cached for the duration on the request cycle (until it is detached - which is usually what you want) and is not aware of the call to delete().
In order to refresh the sampleEntityListModel, add a sampleEntityListModel.detach() call just after the delete (sampleEntityListModel must be made final, but this will not cause any extra state to be serialized). This will cause the model to fetch a fresh set of data when the list view is rendered later in the request cycle.

You probably want an AjaxLink instead of that Link, and then you have to make the list refresh, using the tactics described here, possibly adjusting a bit for the fact that the wiki has Wicket 1.3 code instead of 1.4.
But you might also be better off with a different repeater, such as a RefreshingView or a DataView. There are some examples of assorted repeaters here. While none of them are exactly what you're looking for, looking at that code might help.

looks like the problem is that your mSampleEntityBA.findAll(); is returning incorrect data. hard to help without seeing more code.
on a different note, you should really be using DataView when working with database-backed lists.

You might also want to check out JQGrid from the wiQuery project instead of DataView.