Question

My ultimate goal is to have a JList which refreshes its content at runtime, and I have found a solution that works from this post here on SO, however I am curious why my original idea did not.

As of now, I have something like this setup and it works:

DefaultListModel default = new DefaultListModel();

for(int i = 0; i < array.size() ; ++i){
   test.addElement(array.get(i));
}
list.setModel(default);

Below was my original plan. I wanted to have a class which implemented ListModel be passed as an argument, hoping it would refresh the JList.

SomeClass test = new SomeClass(); //Implements ListModel
list.setModel(test);

or

SomeClass test = new SomeClass(); //Implements ListModel
list = new JList(test);

Neither of these work, which confuses me. Could these last two methods work some how, the code is so much cleaner.

Thanks.

Answer 1

The first approach should work if you implement the ListModel correctly. The key is that when you change the data you need to invoke:

fireContentsChanged(...);

from the AbstractListModel (which I assume you extend). Invoking this method will tell the JList to repaint itself.

The second approach won’t work because you just create a new JList component that is sitting in memory. Creating the component does not add it to the GUI. So if you use this approach you need to remove the original JList from the GUI and then add your new JList to the GUI. This is not very convenient and is a good reason why this approach should not be used. Setting the model is always the preferred approach.