How can I check if multiple checkboxes are checked with JSF / AjaxBehaviorEvent - ajax

Question

I have multiple checkboxes - they are given the same id, "choosen" in the xhtml view code.
I have added an Ajax event listener for them, like so:
<ui:repeat var="posts"
value="#{postBacking.postsOverview.posts}">
<h:selectBooleanCheckbox id="choosen"
styleClass="check-margin"
value="#{posts.choosen}" rendered="#{posts.declined =='No'}">
<f:ajax listener="#{postsBacking.isPostsChosen}" event="click" render="#form" execute="#form"/>
</h:selectBooleanCheckbox>
</ui:repeat>
In the listener method in my backingBean, I would like to check if any of these checkboxes are checked, and then set a button disabled if no checkboxes are marked - and enabled if one or more is set.
But how do I get hold of the values of all checkboxes - can I use the AjaxBehaviorEvent objet for that or is there some other way?

Answer 1

While processing the ajax event listener, the checkbox values should normally have been applied to your data model where you can look up the state of user choice. Depending on that state, simply toggle a boolean bean property which disables the command button:
#Named
#ViewScoped
public class MyBean implements Serializable {
private List<Post> posts;
private boolean buttonDisabled = true;
public void ajaxEventListener(BehaviorEvent e) {
boolean anythingChosen = false;
for (Post post : posts) {
if (post.isChosen() && "No".equals(post.getDeclined())) {
anythingChosen = true;
break;
}
}
// or alternatively using the stream api:
// anythingChosen = posts.stream().filter(Post::isChosen).map(Post::getDeclined)
// .anyMatch("No"::equals);
setButtonDisabled(!anythingChosen);
}
// getters, setters ...
}
Using the following form, the command button is disabled as long as no checkbox is checked:
<h:form>
<ui:repeat var="post" value="#{myBean.posts}">
<h:selectBooleanCheckbox value="#{post.chosen}">
<f:ajax event="click" listener="#{myBean.ajaxEventListener}" render="#form" execute="#form"/>
</h:selectBooleanCheckbox>
</ui:repeat>
<h:commandButton action="#{myBean.doSomething()}" value="doSomething"
disabled="#{myBean.buttonDisabled}" />
</h:form>

Answer 2

You can use valueChangeListener rather than using listener and event attributes. The valueChangeListener will be triggered every time you check/uncheck the checkbox.
To get hold of the values when thevalueChangeListener is invoked, you can loop through the postBacking.postsOverview.posts to see if any value is checked.
Don't forget to update the button on <f:ajax render="#form btnId"/> to enable/ disable it.