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Keeping top displayed node the same during tree refreshing [message #778264]

Thu, 12 January 2012 03:03

Missing name Mising name

Messages: 105
Registered: December 2010

Senior Member

I have a Tree view with lots of nodes.
Sometimes a notification comes in of a change to the root node.
Since the new node is a new object, I can't just updated it. I have to do a setInput() and replace the tree.
I'd LIKE to be able to rescroll the tree so the same "value" is still at the top of the view.
So far I haven't found any way to do that.
I can use TreeViewer.getTree().getTopItem() to get the top item before the setInput().
I then get the data item value so I know what needs to be the new top value.
I just haven't found any way to use setTopItem() to restore the state, since all the TreeItems will be new now.
There doesn't seem to be a way to find the new TreeItem that has the correct data value, so I can set it to be the top item.

Any suggestions?

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Re: Keeping top displayed node the same during tree refreshing [message #778448 is a reply to message #778264]

Thu, 12 January 2012 07:53

Thomas Schindl

Messages: 6651
Registered: July 2009

Senior Member

Am 12.01.12 04:03, schrieb Missing name Mising name:
> I have a Tree view with lots of nodes.
> Sometimes a notification comes in of a change to the root node. Since
> the new node is a new object, I can't just updated it. I have to do a
> setInput() and replace the tree.

You can call add!

> I'd LIKE to be able to rescroll the tree so the same "value" is still at
> the top of the view.
> So far I haven't found any way to do that.
> I can use TreeViewer.getTree().getTopItem() to get the top item before
> the setInput().
> I then get the data item value so I know what needs to be the new top
> value.
> I just haven't found any way to use setTopItem() to restore the state,
> since all the TreeItems will be new now.

You can remember the domain object instead using TreeItem.getData, after
the refresh you search for the item (problem is that nested items are
created lazily!)

Bottomline: I think you should use the add/remove API.

Tom

> There doesn't seem to be a way to find the new TreeItem that has the
> correct data value, so I can set it to be the top item.
>
> Any suggestions?
>

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Re: Keeping top displayed node the same during tree refreshing [message #778491 is a reply to message #778448]

Thu, 12 January 2012 20:54

Missing name Mising name

Messages: 105
Registered: December 2010

Senior Member

Add doesn't seem relevant.
This isn't a new node that's being added to the tree.
I need to REPLACE the existing node.
And sometimes the node being replaced is the root node.

Even if I'm not replacing the root node, but 1 level down, I have to refresh the root, which looses the current view position.

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