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Eclipse supports Drag and Drop based on transfer types defined as a subclass "org.eclipse.swt.dnd.Transfer". Every UI element can define if it provides a certain transfer type as source and if it accepts a certain transfer type as destination.

Eclipse provides several pre-defined transfer types, to define your own transfer type it is recommended to subclass "org.eclipse.swt.dnd.ByteArrayTransfer".

The following will demonstrate the usage of drag and drop for your own domain object between two JFace viewers (table and tree). The example in this article will just transfer Text. For a comprehensive description of drag and drop please check the articles in the appendix.

Create a new Eclipse RCP project "de.vogella.dnd.jface" with two views.

See Eclipes RCP for information on how to create Eclipse RCP applications and views.

Create the following model class.

			
package de.vogella.dnd.jface.model;

public class Todo {
	private String shortDescription;
	private String longDescription;
	
	public String getShortDescription() {
		return shortDescription;
	}
	public void setShortDescription(String shortDescription) {
		this.shortDescription = shortDescription;
	}
	public String getLongDescription() {
		return longDescription;
	}
	public void setLongDescription(String longDescription) {
		this.longDescription = longDescription;
	}
}

		

Create the following content providers (Singletons).

			
package de.vogella.dnd.jface.model;

import java.util.ArrayList;
import java.util.List;

public enum ContentProvider {
	INSTANCE;
	
	public List<Todo> getModel(){
		List<Todo> list = new ArrayList<Todo>();
		Todo todo = new Todo("Java", "Learn the Closure proposal");
		list.add(todo);
		todo = new Todo("Eclipse", "Learn more about the RCP platform");
		list.add(todo);
		return list;
	}
}

		

			
package de.vogella.dnd.jface.model;

import java.util.ArrayList;
import java.util.List;

public enum ContentProviderTree {
	INSTANCE;
	List<String> list = new ArrayList<String>();
	
	private ContentProviderTree() {
		list.add("Branch1");
		list.add("Branch1");
	}
	
	public List<String> getModel(){
		return list;
	}
}

		

Create the following label and content provider for your JFace viewers.

			
package de.vogella.dnd.jface.viewers;

import java.util.List;

import org.eclipse.jface.viewers.IStructuredContentProvider;
import org.eclipse.jface.viewers.Viewer;

import de.vogella.dnd.jface.model.Todo;

public class TableContentProvider implements IStructuredContentProvider {

	@Override
	public Object[] getElements(Object inputElement) {
		List<Todo> list = (List<Todo>) inputElement;
		return list.toArray();
	}

	@Override
	public void dispose() {
		
	}

	@Override
	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
	}

}

		

			
package de.vogella.dnd.jface.viewers;

import java.util.List;

import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.Viewer;

public class TreeContentProvider implements ITreeContentProvider {

	@Override
	public Object[] getChildren(Object parentElement) {
		return null;
	}

	@Override
	public Object getParent(Object element) {
		return null;
	}

	@Override
	public boolean hasChildren(Object element) {
		return false;
	}

	@Override
	public Object[] getElements(Object inputElement) {
		List<String> list = (List<String>) inputElement;
		return list.toArray();
	}

	@Override
	public void dispose() {
		
	}

	@Override
	public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {
	}

}

		

			
package de.vogella.dnd.jface.viewers;

import org.eclipse.jface.viewers.BaseLabelProvider;
import org.eclipse.jface.viewers.ITableLabelProvider;
import org.eclipse.swt.graphics.Image;

import de.vogella.dnd.jface.model.Todo;

public class TableLabelProvider extends BaseLabelProvider implements
		ITableLabelProvider {

	@Override
	public Image getColumnImage(Object element, int columnIndex) {
		return null;
	}

	@Override
	public String getColumnText(Object element, int columnIndex) {
		Todo todo = (Todo) element;
		switch (columnIndex) {
		case 0:
			return todo.getShortDescription();
		case 1:
			return todo.getLongDescription();
		}
		return "Not supported";
	}

}

		

			
package de.vogella.dnd.jface.viewers;

import org.eclipse.jface.viewers.LabelProvider;


public class TreeLabelProvider extends LabelProvider {
	@Override
	public String getText(Object element) {
		String s = (String) element; 
		return s;
	}

}

		

Create the following Drop and Drag listener which will be later assigned to the views.

			
package de.vogella.dnd.jface.dnd;

import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.DragSourceListener;
import org.eclipse.swt.dnd.TextTransfer;

import de.vogella.dnd.jface.model.Todo;
public class MyDragListener implements DragSourceListener {

	private final TableViewer viewer;

	public MyDragListener(TableViewer viewer) {
		this.viewer = viewer;
	}

	@Override
	public void dragFinished(DragSourceEvent event) {
		System.out.println("Finshed Drag");
	}

	@Override
	public void dragSetData(DragSourceEvent event) {
		// Here you do the convertion to the type which is expected.
		IStructuredSelection selection = (IStructuredSelection) viewer
		.getSelection();
		Todo firstElement = (Todo) selection.getFirstElement();
		
		if (TextTransfer.getInstance().isSupportedType(event.dataType)) {
			event.data = firstElement.getShortDescription() + " " + firstElement.getLongDescription(); 
		}

	}

	@Override
	public void dragStart(DragSourceEvent event) {
		System.out.println("Start Drag");
	}

}

		

			
package de.vogella.dnd.jface.dnd;

import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerDropAdapter;
import org.eclipse.swt.dnd.DropTargetEvent;
import org.eclipse.swt.dnd.TransferData;

import de.vogella.dnd.jface.model.ContentProviderTree;

public class MyDropListener extends ViewerDropAdapter {

	private final Viewer viewer;

	public MyDropListener(Viewer viewer) {
		super(viewer);
		this.viewer = viewer;
	}

	@Override
	public void drop(DropTargetEvent event) {
		int location = this.determineLocation(event);
		String target = (String) determineTarget(event);
		String translatedLocation ="";
		switch (location){
		case 1 :
			translatedLocation = "Dropped before the target ";
			break;
		case 2 :
			translatedLocation = "Dropped after the target ";
			break;
		case 3 :
			translatedLocation = "Dropped on the target ";
			break;
		case 4 :
			translatedLocation = "Dropped into nothing ";
			break;
		}
		System.out.println(translatedLocation);
		System.out.println("The drop was done on the element: " + target );
		super.drop(event);
	}

	// This method performs the actual drop
	// We simply add the String we receive to the model and trigger a refresh of the 
	// viewer by calling its setInput method.
	@Override
	public boolean performDrop(Object data) {
		ContentProviderTree.INSTANCE.getModel().add( data.toString());
		viewer.setInput(ContentProviderTree.INSTANCE.getModel());
		return false;
	}

	@Override
	public boolean validateDrop(Object target, int operation,
			TransferData transferType) {
		return true;
		
	}

	

}

		

Adjust your views. The first view will show a table and will allow that elements will be dragged from it. The second view accepts drops.

			
package de.vogella.dnd.jface.view;

import org.eclipse.jface.viewers.TableViewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.TextTransfer;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.ui.part.ViewPart;

import de.vogella.dnd.jface.dnd.MyDragListener;
import de.vogella.dnd.jface.model.ContentProvider;
import de.vogella.dnd.jface.viewers.TableContentProvider;
import de.vogella.dnd.jface.viewers.TableLabelProvider;

public class TableView extends ViewPart {


	@Override
	public void createPartControl(Composite parent) {
		TableViewer viewer = new TableViewer(parent, SWT.MULTI | SWT.H_SCROLL
				| SWT.V_SCROLL);
		int operations = DND.DROP_COPY| DND.DROP_MOVE;
		Transfer[] transferTypes = new Transfer[]{TextTransfer.getInstance()};
		viewer.addDragSupport(operations, transferTypes , new MyDragListener(viewer));
		viewer.setContentProvider(new TableContentProvider());
		viewer.setLabelProvider(new TableLabelProvider());
		viewer.setInput(ContentProvider.INSTANCE.getModel());
	}

	@Override
	public void setFocus() {

	}

}

		

			
package de.vogella.dnd.jface.view;

import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.TextTransfer;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.ui.part.ViewPart;

import de.vogella.dnd.jface.dnd.MyDropListener;
import de.vogella.dnd.jface.model.ContentProviderTree;
import de.vogella.dnd.jface.viewers.TreeContentProvider;
import de.vogella.dnd.jface.viewers.TreeLabelProvider;

public class TreeView extends ViewPart {

	@Override
	public void createPartControl(Composite parent) {
		TreeViewer viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL
				| SWT.V_SCROLL);
		int operations = DND.DROP_COPY | DND.DROP_MOVE;
		Transfer[] transferTypes = new Transfer[]{TextTransfer.getInstance()};
		viewer.addDropSupport(operations, transferTypes, new MyDropListener(viewer));
		viewer.setContentProvider(new TreeContentProvider());
		viewer.setLabelProvider(new TreeLabelProvider());
		viewer.setInput(ContentProviderTree.INSTANCE.getModel());
	}
	
	@Override
	public void setFocus() {
	}


}

		

Thank you for practicing with this tutorial.

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