How Reliable Is EventListenerList Listener Invocation Order in Swing Applications?

EventListenerList Listener Invocation Order

In Swing applications, event listeners are registered in an EventListenerList, which manages the order in which listeners are notified. While the EventListenerList documentation suggests a specific notification order, it's not guaranteed.

Expected vs. Observed Order

In the example provided, the parent listener was added to the slider before the local listener. This is expected behavior, as the documentation states that listeners are notified in the order they are added. However, it's not a guarantee.

Reliability Concerns

The documentation for JSlider and JComponent doesn't specify the listener notification order. This leaves open the possibility that subsequent JRE versions could change the order, causing unexpected behavior.

Recommended Approach

To ensure consistent results, it's recommended to set up a chain of listeners. This way, you can control the order of listener invocation by having each listener forward the event to the next listener in the chain. By implementing this chaining approach, you can enforce the desired notification order more reliably.

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