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Items changed event for JavaFX ListView control

I am looking for something like an Item Changed Event or Item Count Changed Event for JavaFX ListView control or lets just say in general for any collection type control.
It is because, I have some Buttons, that I want to be enabled only when there is at least one item in ListView otherwise that Button should be in disabled state.
It is my guess that perhaps adding a ChangeListener to the ListView control. would that be a right approach.
Any suggestions how can we achieve this.

The JavaFX Listview provides a method with the signature
public final ObservableList<T> getItems()
You can add a listener to the observable list which will be called whenever items are added to or removed from the ListView.
aListView.getItems().addListener(new ListChangeListener() {
#Override
public void onChanged(ListChangeListener.Change change) {
System.out.println("Detected a change! ");
}
});
Similar functionality is also provided by the other 'collection' controls.

Add a binding based on the ListView items using Bindings.isEmpty
button.disableProperty().bind(Bindings.isEmpty(listView.getItems()));

This will also work when someone calls ListView#setItems and completely changes the observable list:
InvalidationListener updateScrollBarListener = ...
aListView.itemsProperty().addListener((obs, old, current) -> {
if(old != null) {
old.removeListener(updateScrollBarListener);
}
if(current != null) {
current.addListener(updateScrollBarListener);
}
});
I've been looking for a way to to make this a bit shorter (perhaps with Bindings) but haven't found it so far.

GWT - how to get the tabText of selected tab?

I want to get the tab text when I click on a tab. I do this:
tabPanel.addSelectionHandler(new SelectionHandler<Integer>() {
#Override
public void onSelection(SelectionEvent<Integer> event) {
//get the tabtext here
}
});
But I only get the index.

Assuming you are using TabPanel and you haven't provided a custom Widget for the TabBar, you could do this:
tabPanel.addSelectionHandler(new SelectionHandler<Integer>() {
#Override
public void onSelection(SelectionEvent<Integer> event) {
String tabHtml = tabPanel.getTabBar().getTabHTML(event.getSelectedItem());
}
});
Of course, you will get the underlying HTML of the tab, that generally is a <div>tab text</div>. The text you put in the add() methods are wrapped in either a Label, or an HTML widget, whether you have chosen to display the tab text as HTML.
Of course this is not handy, generally you need to store somewhere the tab text (in a TabPanel extension I'd guess, or a model) at insertion time (overriding the add(...)s) and retrieve it when needed (by adding a simple getter for them).

You can get the selected tab by following.
tabPanel.getElement().getTitle();

GWT equivalent of jQuery change() for form elements

Can anyone tell me whether there is an equivalent method in GWT like change in jQuery for form elements like radio-buttons, checkboxes, etc, which is fired the moment any such button is checked or unchecked? If so, how do I use it? I found a method like addValueChangeHandler in the Google docs, but apart from providing the prototype, there is no working example.
Specifically, if I want a handler which will wait for a checkbox being checked or unchecked, and accordingly pop up an alert like A checkbox has been checked!!, along with that buttons accompanying text.

CheckBox newOption = new CheckBox();
newOption.setText("Check to see alert");
newOption.addValueChangeHandler(new ValueChangeHandler<Boolean>() {
#Override
public void onValueChange(ValueChangeEvent<Boolean> event) {
if (event.getValue()) {
Window.alert("Checkbox is checked!");
} else {
Window.alert("Checkbox is unchecked!");
}
}
});

Wicket - updating ListView using AJAX and Wicket Model

I have a :
Client Class
ListView
TextField
I need to populate my ListView in order to form a table:
WORKING CODE:
clientModel = new LoadableDetachableModel() {
#Override
protected Object load() {
return Client.getClientListByCompanyName(searchClientInput.getValue());
}
};
searchClientInput.setModel(new Model<String>());
searchClientInput.add(new AjaxFormComponentUpdatingBehavior("onkeyup") {
#Override
protected void onUpdate(AjaxRequestTarget target) {
target.add(clientListViewContainer);
}
});
clientListView = new ListView<Client>(CLIENT_ROW_LIST_ID, clientModel) {
#Override
protected void populateItem(ListItem<Client> item) {
Client client = item.getModelObject();
item.add(new Label(CLIENT_ROW_COMPANY_CNPJ_ID, client.getCompanyName()));
item.add(new Label(CLIENT_ROW_COMPANY_NAME_ID, client.getCompanyCnpj()));
}
};
clientListViewContainer.setOutputMarkupId(true);
clientListViewContainer.add(clientListView);
add(clientListViewContainer);
Now, in my HTML, I have a TextField. Whenever an user types something in this TextField, a select will be made in the database with whatever he typed. So for each word, a select is made, and the table needs to be updated. I am guessing I will need to use AJAX and possibly a Model. I'm kind of lost about how I can do this, if someone can provide me examples I would be very grateful.
EDIT: New code that is throwing exception: Last cause: Attempt to set model object on null model of component: searchClientForm:searchClientInput
EDIT 2: Ok so the exception was that my TextField didn't had a model to bind data to. So what I did was: searchClientInput.setModel(new Model<String>());
I also had a problem with the event. Using onkeydown was working, but not as intended. I had Company Name 1-4. If I typed Company Name 1, I would need to press one key again so the table would get updated. With onkeyup this don't happens. Thanks for the help.

You could give the ListView a LoadableDetachableModel which provides the selected clients matching your TextField's value.
Use an AjaxFormComponentUpdatingBehavior on your TextField which add a parent of the ListView to the request target (don't forget #setOutputMarkupId().

I believe the best way to perform what you want (which is repainting a table/list at each input change --> DB access) is with a DataView and a DataProvider.
A DataView is just like the ListView component except it uses an IDataProvider to get the data you want to present. You are able to implement the DataProvider so it accesses your DB, and you can add restrictions (where clauses) to the DataProvider.
[this is more like pseudo-code]
public final class MyDataProvider<T> extends SortableDataProvider<T> {
// ...
Set filters;
// filters is the set where the restrictions you want to apply are stored
...
#Override
public Iterator<T> iterator(int first, int count) {
// DAO (Data Access Object) access to DB
// ...
return dao.findByRestrictions(filters).iterator();
}
...
}
Now on the ajax event on your input component you are able to update the filter being used in the DataProvider, and in the the next repaint of the DataView, the provider will "pull" the data matching the restrictions defined in the filter.
Hope it helps. Best regards.

GWT SuggestBox: How do I force the SuggestBox to select the first item in the suggestion list?

I have a textbox and one suggestbox. I attach a value change and key up handler to the text box such that whatever the user types (or pastes) into the text box is echo-ed inside the suggestbox. I can get the suggestbox to display the suggestion list by calling showSuggestionList on each value change and key up event.
Now, how do I get the suggestbox to automatically choose the first item in the suggestion list?
One of the methods I tried is to programatically simulate key presses, i.e
suggestBox.setFocus(true);
NativeEvent enterEvent = Document.get().createKeyPressEvent(false, false, false, false, KeyCodes.KEY_ENTER);
DomEvent.fireNativeEvent(enterEvent, suggestBox);
textBox.setFocus(true);
This doesn't work at all. The enter key isn't simulated. Another possible solution is to extend SuggestionBox.SuggestionDisplay, but I'm not too sure how to that. Any pointers appreciated.
Update: I'm still working on this and trying various methods.
Here, I tried to implement my own SuggestionDisplay by subclassing DefaultSuggestionDisplay and overriding getCurrentSelection() to make accessible from my class. This doesn't work either. Null is returned.
private class CustomSuggestionDisplay extends DefaultSuggestionDisplay {
#Override
protected Suggestion getCurrentSelection() {
return super.getCurrentSelection();
}
}
suggestBox.setAutoSelectEnabled(true);
textBox.addKeyUpHandler(new KeyUpHandler() {
public void onKeyUp(KeyUpEvent event) {
suggestBox.setValue(textBox.getText(), true);
suggestBox.showSuggestionList();
if (suggestBox.isSuggestionListShowing()) {
String s = ((CustomSuggestionDisplay) suggestBox.getSuggestionDisplay()).getCurrentSelection().getDisplayString();
Window.alert(s);
}
}
});
Here, I tried to attach a value change handler to the SuggestBox, and casting the event type to SuggestOracle.Suggestion. Again, null is returned.
suggestBox.addValueChangeHandler(new ValueChangeHandler<String>() {
public void onValueChange(ValueChangeEvent<String> event) {
String s = ((SuggestOracle.Suggestion) event).getDisplayString();
Window.alert(s);
}
});

Use suggesBox.setAutoSelectEnabled(true)
Here more info about the SuggestBox of GWT:

You could try using addSelectionHandler in conjunction with setAutoSelectEnabled to receive an event whenever a suggestion is selected. You could also have your Oracle send a message when it suggests something, or your Display send a message when it displays a list:
public class AutomaticallySelectingSuggestionDisplay extends SuggestBox.DefaultSuggestionDisplay {
#Override
protected void showSuggestions(SuggestBox box, Collection<? extends SuggestOracle.Suggestion> suggestions, boolean isDisplayHtml, boolean isAutoSelectEnabled, SuggestBox.SuggestionCallback callback) {
super.showSuggestions(box, suggestions, isDisplayHtml, isAutoSelectEnabled, callback);
fireValueChangeEventWithFirstSuggestion(suggestions);
}
}
This idea feels a little muddled to me, so I hope you can find a solution just using event handlers.