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how (and when) are view constructed? [message #512762]

Sun, 07 February 2010 05:37

Eclipse User

I'm curious to know when are view instantiated during the application lifecycle, since the layout factory simply refers to their ID I believe the view is created when first used in a perspective. And what are the constraints on view constructors? For instace, is it possible to use a factory method to create a view?

Re: how (and when) are view constructed? [message #512822 is a reply to message #512762]

Mon, 08 February 2010 00:51

Eclipse User

On 07/02/10 4:07 PM, Luca Ferrari wrote:
> I'm curious to know when are view instantiated during the application
> lifecycle, since the layout factory simply refers to their ID I believe
> the view is created when first used in a perspective. And what are the
> constraints on view constructors? For instace, is it possible to use a
> factory method to create a view?
>

You are right. A viewpart is instantiated only when it is required.
Even if its added to a perspective, it won't be instantiated if its not
visible initially (some other view is active and visible in the same folder)

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- Prakash
Platform UI Team, IBM

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Re: how (and when) are view constructed? [message #512910 is a reply to message #512822]

Mon, 08 February 2010 05:48

Eclipse User

But is there a way to instrument eclipse to use afactory method (something like getInstance()) instead of the default constructor?
Moreover, can I assume a view is always a singleton in the rcp platform?

Re: how (and when) are view constructed? [message #513009 is a reply to message #512910]

Mon, 08 February 2010 10:02

Eclipse User

Luca Ferrari wrote:
> But is there a way to instrument eclipse to use afactory method
> (something like getInstance()) instead of the default constructor?
> Moreover, can I assume a view is always a singleton in the rcp platform?

It's never that simple :-)

A view is constructed when it is show for the first time in a
perspective (either because it's part of the perspective or because of a
user showView).

Lifecycle:
no-arg constructor
init(*)
createPartControl(*)
....
dispose()

Within one window, there will only be one instance of a view with that
exact ID (one outline view, for example). But if you open 2 windows,
you can have 2 outline view instances. Closing a view (so it is
disposed) and then opening the view again causes a new instances to be
created (the other already being disposed).

You *could* use org.eclipse.core.runtime.IExecutableExtensionFactory
instead of the view class to allow more control over instantiating the
view itself ... except when create() is called it still has to be
unique, as there's no way to tell what the framework will use it for.

Later,
PW

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