On Fri, 7 Oct 2022 20:50:55 GMT, Andy Goryachev <ango...@openjdk.org> wrote:
> Introduction > > There is a number of places where various listeners (strong as well as weak) > are added, to be later disconnected in one go. For example, Skin > implementations use dispose() method to clean up the listeners installed in > the corresponding Control (sometimes using > LambdaMultiplePropertyChangeListenerHandler class). > > This pattern is also used by app developers, but there is no public utility > class to do that, so every one must invent their own, see for instance > https://github.com/andy-goryachev/FxTextEditor/blob/master/src/goryachev/fx/FxDisconnector.java > > Proposal > > It might be beneficial to create a class (ListenerHelper, feel free to > suggest a better name) which: > > - provides convenient methods like addChangeListener, > addInvalidationListener, addWeakChangeListener, etc. > - keeps track of the listeners and the corresponding ObservableValues > - provides a single disconnect() method to remove all the listeners in one go. > - optionally, it should be possible to add a lambda (Runnable) to a group of > properties > - optionally, there should be a boolean flag to fire the lambda immediately > - strongly suggest implementing an IDisconnectable functional interface with > a single disconnect() method > > Make it Public Later > > Initially, I think we could place the new class in package > com.sun.javafx.scene.control; to be made publicly accessible later. > > Where It Will Be Useful > > [JDK-8294589](https://bugs.openjdk.org/browse/JDK-8294589) "MenuBarSkin: > memory leak when changing skin" > and other skins, as a replacement for > LambdaMultiplePropertyChangeListenerHandler. > > https://github.com/openjdk/jfx/pull/908#:~:text=19%20hours%20ago-,8295175%3A%20SplitPaneSkinSkin%3A%20memory%20leak%20when%20changing%20skin%20%23911,-Draft > > https://github.com/openjdk/jfx/pull/914 Thank you @nlisker and @hjohn for providing the link and explanations. You are right, ListenerHelper is somewhat similar to Subscription in that it allows for quick disconnect(). It is, however, designed for a different purpose, that goes beyond what is needed from a simple listener management. Specifically, - it assumes multiple listeners/handlers/callbacks from the start - it allows for invoking listeners/callbacks immediately as it is a frequent pattern not only in Skins but also in application code (I do want to make this class a part of public API eventually) - unlike Subscription, we can addEventHandlers and addEventFilters - unlike Subscription, we can add Weak listeners/callbacks, though I admit it might be a design decision to use or not to use that to summarize, I see some minor overlap between Subscription and ListenerHelper, but mostly these are two different beasts designed for two different purposes. I do agree with the call to cooperate! Would love to. what do you think? ------------- PR: https://git.openjdk.org/jfx/pull/908
