Yeah, I've been doing some investigating.
Using the below example, when the "Refresh Menu" button is clicked, it will
replace the items making the old one collectable by the GC.
If the Menu was never used/drop down shown, it will get collected.
If it was used (just shown), it remains in memory (seen on VisualVM).
GC Root points to ContextMenuContent.MenuItemContainer
@Override
public void start(Stage primaryStage) {
this.primaryStage = primaryStage;
primaryStage.setTitle("Hello World!");
Button btn = new Button("New Stage");
Button btnRefresh = new Button("Refresh Menu");
ButtonBar buttonBar = new ButtonBar();
buttonBar.getButtons().addAll(menu, btnRefresh);
btnRefresh.setOnAction(e -> {
menu.getItems().setAll(getMenuItem());
});
Scene scene = new Scene(buttonBar);
primaryStage.setScene(scene);
primaryStage.show();
menu.getItems().add(getMenuItem());
}
private MenuItem getMenuItem() {
MenuItem item = new MenuItem();
item.setText("Menu Item");
item.setOnAction(a -> {
System.out.println("ACTION");
});
return item;
}
Em sáb., 20 de abr. de 2024 às 05:01, John Hendrikx <john.hendr...@gmail.com>
escreveu:
> I think this code is bug free, and the added fix shouldn't be needed --
> the old MenuItems should be cleaned up, and so should the referenced Stages.
>
> So I think the bug is elsewhere, maybe not even in your code at all. I did
> see PR's dealing with how MenuItems are linked to their platform specific
> counterparts and how that can be a bit messy. I'm starting to suspect
> maybe the MenuItems themselves are somehow still referenced (perhaps only
> when they've been displayed once). These should also be GC'd. They are
> however much smaller, so as long as they don't reference a Stage it is
> probably not noticeable memory wise.
>
> An inspection with VisualVM should give an answer (or you could make a
> MenuItem very large by attaching some huge objects to it that are not
> referenced elsewhere, via its properties map for example).
>
> --John
> On 19/04/2024 14:47, Thiago Milczarek Sayão wrote:
>
> When the window list changes, I'm calling item.setOnAction(null) on the
> "old list" before inserting a new one.
> In general it's not a problem because the menu item or button is in a
> "context", like a Stage and everything is freed when the stage is closed.
> Maybe on long lasting stages.
>
> The code goes like this:
>
> Window.getWindows().addListener((ListChangeListener<? super Window>) change
> -> updateWindowList());
>
>
> private void updateWindowList() {
> Window[] windows = Window.getWindows().toArray(new Window[] {});
>
> List<MenuItem> items = new ArrayList<>();
> for (Window window : windows) {
> if (window instanceof Stage stage && stage != primaryStage) {
> MenuItem item = new MenuItem();
> item.setText(stage.getTitle());
> item.setOnAction(a -> stage.toFront());
> item.setGraphic(new FontIcon());
> items.add(item);
> }
> }
>
> for (MenuItem item : btnWindows.getItems()) {
> item.setOnAction(null);
> }
>
> btnWindows.getItems().setAll(items);
> }
>
>
> Maybe there's a bug, because the old list of items is collectable.
>
>
>
> Em sex., 19 de abr. de 2024 às 01:37, John Hendrikx <
> john.hendr...@gmail.com> escreveu:
>
>> This probably is a common mistake, however the Weak wrapper is also easy
>> to use wrongly. You can't just wrap it like you are doing in your example,
>> because this is how the references look:
>>
>> menuItem ---> WeakEventHandler ---weakly---> Lambda
>>
>> In effect, the Lambda is weakly referenced, and is the only reference, so
>> it can be cleaned up immediately (or whenever the GC decides to run) and
>> your menu item will stop working at a random time in the future. The
>> WeakEventHandler will remain, but only as a stub (and gets cleaned up when
>> the listener list gets manipulated again at a later stage).
>>
>> The normal way to use a Weak wrapper is to put a reference to the wrapped
>> part in a private field, which in your case would not solve the problem.
>>
>> I'm assuming however that you are also removing the menu item from the
>> Open Windows list. This menu item should be cleaned up fully, and so the
>> reference to the Stage should also disappear. I'm wondering why that isn't
>> happening? If the removed menu item remains referenced somehow, then it's
>> Action will reference the Stage, which in turns keeps the Stage in memory.
>>
>> I'd look into the above first before trying other solutions.
>>
>> --John
>>
>>
>> On 18/04/2024 17:50, Thiago Milczarek Sayão wrote:
>>
>> I was investigating,
>>
>> It probably should be menuItem.setOnAction(new WeakEventHandler<>(e ->
>> stage.toFront()));
>>
>> But I bet it's a common mistake. Maybe the setOnAction should mention it?
>>
>>
>>
>> Em qui., 18 de abr. de 2024 às 11:54, Andy Goryachev <
>> andy.goryac...@oracle.com> escreveu:
>>
>>> You are correct - the lambda strongly references `stage` and since it is
>>> in turn is strongly referenced from the menu item it creates a leak.
>>>
>>>
>>>
>>> The lambda is essentially this:
>>>
>>>
>>>
>>> menuItem.setOnAction(new H(stage));
>>>
>>> class $1 implements EventHandler<ActionEvent> {
>>>
>>> private final Stage stage;
>>>
>>> public $1(Stage s) {
>>>
>>> this.stage = s; // holds the reference and causes the leak
>>>
>>> }
>>>
>>> public void handle(ActionEvent ev) {
>>>
>>> stage.toFront();
>>>
>>> }
>>>
>>> }
>>>
>>>
>>>
>>> -andy
>>>
>>>
>>>
>>> *From: *openjfx-dev <openjfx-dev-r...@openjdk.org> on behalf of Thiago
>>> Milczarek Sayão <thiago.sa...@gmail.com>
>>> *Date: *Thursday, April 18, 2024 at 03:42
>>> *To: *openjfx-dev <openjfx-dev@openjdk.org>
>>> *Subject: *Possible leak on setOnAction
>>>
>>> Hi,
>>>
>>>
>>>
>>> I'm pretty sure setOnAction is holding references.
>>>
>>>
>>>
>>> I have a "Open Windows" menu on my application where it lists the Stages
>>> opened and if you click, it calls stage.toFront():
>>>
>>>
>>>
>>> menuItem.seOnAction(e -> stage.toFront())
>>>
>>>
>>>
>>> I had many crash reports, all OOM. I got the hprof files and analyzed
>>> them - turns out this was holding references to all closed stages.
>>>
>>>
>>>
>>> To fix it, I call setOnAction(null) when the stage is closed.
>>>
>>>
>>>
>>> I will investigate further and provide an example.
>>>
>>>
>>>
>>> -- Thiago.
>>>
>>
