# DragAndDropService

DragAndDropService provides means to implement drag-n-drop behavior in a diagram editor.

Example

    public class MapDragAndDropService extends DragAndDropService
    {
        @Override
        public boolean droppable( DropContext context )
        {
            return context.object() instanceof IFile;
        }

        @Override
        public void drop( DropContext context )
        {
            IFile file = (IFile) context.object();
            List<String> locations = new ArrayList<String>();

            try( BufferedReader br = new BufferedReader( new InputStreamReader( file.getContents() ) );
            {
                for( String line = br.readLine(); line != null; line = br.readLine() )
                {
                    if( line != null )
                    {
                        line = line.trim();

                        if( line.length() > 0 )
                        {
                            locations.add( line );
                        }
                    }
                }
            }
            catch( CoreException e )
            {
                LoggingService.log( e );
            }
            catch( IOException e )
            {
                LoggingService.log( e );
            }

            if( ! locations.isEmpty() )
            {
                SapphireDiagramEditorPagePart diagram = context( SapphireDiagramEditorPagePart.class );
                Map map = context( Map.class );

                Point initialDropPosition = context.position();

                int x = initialDropPosition.getX();
                int y = initialDropPosition.getY();

                for( String locationName : locations )
                {
                    if( ! map.hasLocation( locationName ) )
                    {
                        Location location = map.getLocations().insert();
                        location.setName( locationName );

                        DiagramNodePart locationNodePart = diagram.getDiagramNodePart(location);
                        locationNodePart.setNodeBounds( x, y );

                        x += 50;
                        y += 50;
                    }
                }
            }
        }
    }

The DragAndDropService is typically registered as part of diagram page definition in the sdef file.

    <diagram-page>
        <service>
            <implementation>MapDropService</implementation>
        </service>
    </diagram-page>

Copyright (c) 2016 Oracle
Content made available under the terms of Eclipse Public License.