Question

I have a GUI with nested panels(tabbed with nested panels and etc). I need to pass domain object to deeply nested panel. I can think of two ways:

• Instantiate all gui objects in one place, like frame class. That
  would make passing domain objects dead simple, but Frame class will
  be huge and hardly maintanable.

• Each panel has its own class, where we instantiate and layout its
  components. Now its easy to maintain and classes are clean, but how
  do I pass down the chain my domain objects? I dont want to chain-pass
  them through constructors of panels that shouldn’t even know their
  existance. And top level panels would have a ton of these objects to
  start with.

Niether way seems like a soulution. How do you usually aproach this?

Answer 1

When I put together a Java Swing GUI, I have a data model for each major GUI element. Note that this isn’t an MVC pattern. This is more like a local MV pattern. If you want, you can consider GUI element listeners as the “controller”.

Each panel has its own class, where we instantiate and layout its
components. Now its easy to maintain and classes are clean, but how
do I pass down the chain my domain objects?

You have the right idea, although you shouldn’t have to do much passing.

My JFrame (or JApplet) will have an associated model class of global type fields. An instance of this model class will usually be passed along to the children elements. This is to allow children elements to react properly when a menu option is selected (as an example)

My JPanel(s) will have an associated model class that maintains the state of text or button children elements.

More complicated children elements, like a JList or a JTree, already have an associated data model. I will probably wrap these associated data models into the JPanel model class for convenience.

The children elements will trigger some sort of selection or action listener. Some of these listeners might need access to model classes besides the model class associated with the parent. In this case, you’re going to have to pass the instances of your model classes to the listeners.