Drag & Drop between Swing components and Nodes

[Marco Ehrentreich]

Hi folks,

first of all sorry for annoying you again with this problem I already
posted this question a few weeks ago but I neither got an answer which
solved my problem nor could I come up with a solution on my own.

I have the following problem: In my NetBeans application my main view is
a JTable implementation which displays some kind of application specific
objects. A second window provides an explorer view based on the Nodes
API which displays some other objects. Now I want to enable drag & drop
from the JTable to certain Nodes in the explorer view. The curious thing
is that the drag & drop data transfer is already working! I have
implemented the necessary functionality to link objects of the table to
nodes in the explorer using drag & drop. Unfortunately the mouse cursor
doesn't change its appearance when a drop should be accepted. The cursor
always shows the "forbidden" icon.

For this I would guess I have implemented drag & drop correctly but not
the NetBeans way which is needed to work with Nodes. Unfortunately I
couldn't find any advices how the "drop" part for nodes has to be
configured to show the correct behaviour/icon for accepted and not
accepted drops. Can anyone please tell me what I have to do to get this
right?

Besides this problem I'm going to have another drag & drop feature
between pure nodes in the same explorer view. So I'd be interested in
both - the drag AND the drop implementation in Node classes.

Thanks in advance!

Marco

[StudentB]

I don't have an answer because I am having similar problems. I am trying to
get drag and drop working between two BeanTree Views, each in their own Top
component. I have read through every tutorial and book I can find and its
more confusing then helpful. I actually have the drag and drop partially
working as well but some things I notice. I always get the "can not drop"
icon. The image of the node being drug is not displayed during the
dragging. The tutorials talk about implementing a setDropTarget on a JPanel
and then adding code to the doDragOver to get the image to be displayed but
with the BeanTree View it is already implementing those methods and
subsequently calling getDropType on the target node; therefore I can't add
my code to display the image. I would think that the getIcon method would
be automactially called on the object in the transferrable to display the
image during the dragging. I also noticed that createPasteTypes is never
called so I don't see how the DataFlavors even comes in to play as it
mentions in the tutorials. Lastly, when I want to drag a node the first
time, I first have to single click somewhere in the scroll pane(BreanTree
view) and then click again on the node I want to drag and drag it. If I
don't click in the scroll pane first then dragging does not work. Calling
requestFocus, requestActive, setEnabled does not help. Also, I have noticed
that when the getDropType method is called the action value is some huge
number for a move when it should be a 2.

Sorry for not answering your question but maybe someone will read this and
realize that more than one person could use some help in this area.



erisch wrote:

[Wade Chandler]

Maybe you guys can find something in Geertjan's blog:
http://onesearch.sun.com/search/blog/index.jsp?col=blog&charset=utf-8&weblog=geertjan&qt=drag+and+drop

He has lots of examples from different versions of the IDE. If those don't help, he might be able to point you to some kind of other working examples.

Wade

==================
Wade Chandler, CCE
Software Engineer and Developer, Certified Forensic Computer Examiner, NetBeans Dream Team Member, and NetBeans Board Member
http://www.certified-computer-examiner.com
http://wiki.netbeans.org/wiki/view/NetBeansDreamTeam
http://www.netbeans.org



----- Original Message ----

[Marco Ehrentreich]

Hi,

@Wade: Thanks for the link. There are indeed some useful information on
these pages but unfortunately none could solve or explain my problem :(

Anyway after experimenting some hours and testing all advices from all
tutorials I could find I finally have discovered by accident how to
change my d&d cursor to an accepting one. In my case it was the d&d
action I used before. From a logical view I thouhgt the LINK action
would describe the action in my application most reasonable. But for any
reasons the DndConstants.LINK action always leads to a non-accepting
cursor when trying to drop something on my Nodes within a BeanTreeView.
All the examples and description I found didn't help anything. Only
after I changed the action to COPY I got an accepting cursor.

But it's really frustrating that nobody can explain why it behaves like
this or if and how one could change that. Moreover I couldn't find any
examples which show how to use plain Swing components as drag source and
drop onto NetBeans targets. Is this situation such uncommon?!? The
NetBeans platform is really helpful in many, many ways but simple
problems like this may cost hours or days without finally finding a real
answer... How do you all handle these situations when you really don't
know what else you can do about a problem but you have to get done
something?

@StudentB: After investigating most tutorials on the internet once again
I found those two most useful. Unfortunately the second is in German but
perhaps it may help, too:

http://platform.netbeans.org/tutorials/nbm-nodesapi3.html
http://www.sepix.de/blogs/blogrittner/blog/archive////beandev_minimaler_einsatz_fuer_drag_and_drop_von_nodes/index.html

I hope you can solve you problems with this drag & drop thing.
Unfortunately I can't really help you. I tested all the changes in the
code described in any tutorial and example. As I wrote I finally figured
out that (at least in my application) it was simply this damn drag
action which doesn't produce an "accepting" cursor when dropped on a
node tree. Good Luck!

Marco


Wade Chandler schrieb:

[Wade Chandler]

----- Original Message ----

[Marco Ehrentreich]

[tomwheeler]

On Wed, Oct 15, 2008 at 3:42 AM, Marco Ehrentreich
<address-removed> wrote:

[Marco Ehrentreich]

Hi Tom,

Tom Wheeler schrieb: