WICKET: Updating a self-made Panel - refresh

Question

ive got the following Problem:
my self-made video-class (extending Panel) doesnt get updated, if its model changes.
Thats the current state:
I got a Class "A" with a ListChoice. This Class creates the Panel "descrPanel", which gets a Model, containing the current selected Item of the ListChoice. It is updated, when the User selects something in the ListChoice (The ListChoice got an AjaxBehaviour, updating the descrPanel via target.add(descrPanel)):
Class A:
PropertyModel<Exercise> currExerciseModel = new PropertyModel<Exercise>(this,"selectedExercise");
final ExerciseDescriptionPanel descrPanel = new ExerciseDescriptionPanel("descrPanelTag", currExerciseModel);
descrPanel.setOutputMarkupId(true);
In Class ExerciseDescriptionPanel, i inserted my self-made Video-Class (extending Panel). Also i inserted a MultiLineLabel:
Class ExerciseDescriptionPanel
public class ExerciseDescriptionPanel extends Panel {
private IModel<Exercise> model;
private Exercise exercise;
public ExerciseDescriptionPanel(String id, IModel<Exercise> model) {
super(id, model);
this.model = model;
MultiLineLabel mll = new MultiLineLabel("mll", new Model() {
#Override
public String getObject() {
if (ExerciseDescriptionPanel.this.getModel().getObject() != null){
return ExerciseDescriptionPanel.this.getModel().getObject().getDescription();
}
else return "";
}
});
add(mll);
Video video = new Video("myVideo", new Model<Exercise>(){
#Override
public Exercise getObject() {
if (ExerciseDescriptionPanel.this.getModel().getObject() != null){
return ExerciseDescriptionPanel.this.getModel().getObject();
}
else return new Exercise();
}
});
add(video);
}
Well, what i dont understand is: While the Description is updated based on the current selection of the ListChoice, the Video-Class just ignores it and keeps returning the "new Exercise()", which schould only be returned at the first load of the ListChoice, when no selection is made.
I also provide you the Video-Class:
Class Video
public class Video extends Panel{
private IModel<Exercise> model;
public Video(String id, IModel<Exercise> model) {
super(id, model);
String src = ((Exercise)model.getObject()).getVideo();
String startPicDest = ((Exercise)model.getObject()).getPicture();
WebMarkupContainer flashSrc = new WebMarkupContainer("flashSrcTag");
flashSrc.add(new AttributeModifier("value", "config={'playlist':['" +
startPicDest +"',{'url':'"+ src +"','autoPlay':false}]}"));
this.add(flashSrc);
setOutputMarkupId(true);
}
}
Ive been searching through the internet for hours now, without finding anything helpful.
Hope you guys are able to give me some solution to this problem. Thanks in regard.
Greetings

Answer 1

You're pulling the exercise out of the model once only:
public Video(String id, IModel<Exercise> model) {
super(id, model);
String src = ((Exercise)model.getObject()).getVideo();
...
}
How is this supposed to be up-to-date when the exercise changes later on?
You have to get the actual value for each render:
WebMarkupContainer flashSrc = new WebMarkupContainer("flashSrcTag") {
public void onComponentTag(ComponentTag tag) {
Exercise temp = (Exercise)model.getObject();
String src = temp.getVideo();
String startPicDest = temp.getPicture();
tag.put("value", String.format("config={'playlist':['%s',{'url':'%s','autoPlay':false}]}", startPicDest, src));
}
};

Answer 2

NOTE: Please ignore this humble try to help you, svenmeier's answer is way better than mine.
I'm not 100% sure if this is true, but could it be related to the difference between your Video being a MarkupContainer and the MultiLineLabel being a WebComponent?
Both the Video and the MultiLineLabel are added to the ExerciseDescriptionPanel in its constructor. If I understand the Wicket documentation correctly, as long as the surrounding Page and thus the ExerciseDescriptionPanel stay the same instance, the markup of the Video will not be regenerated. It says:
A Page renders itself by rendering its associated markup (the html file that sits next to the Page). As MarkupContainer (the superclass for Page) iterates through the markup stream for the associated markup, it looks up components attached to the tags in the markup by id. Since the MarkupContainer (in this case a Page) is already constructed and initialized by onBeginRequest(), the child for each tag should be available in the container. Once the Component is retrieved, it's render() method is called.
Maybe you calling modelChanged() on your Video once you change the Model of your ExerciseDescriptionPanel could indicate that the markup has to be refreshed.