| Default behaviour for find TableItem associated to a TableViewer element [message #330317] |
Fri, 25 July 2008 03:45  |
Eclipse User |
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Hi,
I'm using a TableViewer. Inside the TableViewer I place ArrayList objects.
I had a strange problem. After debugging a while I've discovered that
StructuredViewer#findItem(Object element) fails, it gives me the wrong
index for an element.
The cause is that instead of using reference equality, uses content
equality.
AbstractTableViewer#doFindItem()
So If I ask for the TableItem corresponding to an object whose index is 1,
it returns me the object whose index 0, when it has identical values.
I consider this default behaviour dangerous.
I have redefined the equals method of my ArrayList object:
@Override public boolean equals(Object o) {
return o == this;
}
and now it works ok.
What do the Eclipse experts think?
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| Re: Default behaviour for find TableItem associated to a TableViewer element [message #330579 is a reply to message #330387] |
Mon, 04 August 2008 08:21  |
| Eclipse User |
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File a bug and attach a patch against HEAD with your proposed JavaDoc
comment.
Tom
David Perez schrieb:
> Thanks Boris,
>
> I didn't take into account the hashCode().
>
> Now, my custom row object is like this:
>
> class MyObject extends ArrayList<Object> {
> ....
>
> @Override public boolean equals(Object o) {
> return o == this;
> }
>
> @Override public int hashCode() {
> return System.identityHashCode(this);
> }
> }
>
> It would be nice if the Platform documentation emphasized that the
> equals() method implementation is important.
>
> Boris Bokowski wrote:
>
>> Make sure that you also override hashCode() whenever you override
>> equals().
>
>> If the native equals and hashCode implementation is not what you need
>> in the viewer, you can plug in different implementations, see
>> StructuredViewer.setComparer(IElementComparer).
>
>
--
B e s t S o l u t i o n . at
------------------------------------------------------------ --------
Tom Schindl JFace-Committer
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