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In Qt GUIs it is very convenient use signals & slots - it decouple events passing. When I create some widget that throw signal, I don't have to know in advance who can get it, and later with connect I specify connections.
What is parallel in Java/Swing? Can you point to good resources on this issue?
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It is generally unsafe to provide slots in your QThread subclass, unless you protect the member variables with a mutex. On the other hand, you can safely emit signals from your QThread::run() implementation, because signal emission is thread-safe.
This ensures that truly independent components can be created with Qt. You can connect as many signals as you want to a single slot, and a signal can be connected to as many slots as you need. It is even possible to connect a signal directly to another signal.
All signals and slots have a "void" return value. You cannot return anything that way. This code assumes that there is only one slot that will be connected to the signal.
If none of the existing EventListener implementations meet your requirements, you can create your own custom event. Every JComponent contains a field of type EventListenerList. You can use the approach outlined in the EventListenerList API to enable your custom JComponent subclass to fire your custom event.
Regarding the signal/slot mechanism, Swing has several ways to implement the observer pattern, outlined here.
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This Event Listener tutorial goes through the basics of handling events with listeners.
Connecting your slot for a signal is analogous to adding your EventListener to an event-producing object.
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