SWT Tree Drag and Drop

Eintrag.java

package de.marcphilipp.dnd.model;

public class Eintrag {
	
	private final String description;
	private Gruppe gruppe;
	
	public Eintrag(String description) {
		this.description = description;
	}
	
	public String getDescription() {
		return description;
	}

	public Gruppe getGruppe() {
		return gruppe;
	}

	public void setGruppe(Gruppe gruppe) {
		this.gruppe = gruppe;
	}

	public void resetGruppe() {
		gruppe = null;
	}
	
	@Override
	public String toString() {
		return description;
	}
}

Gruppe.java

package de.marcphilipp.dnd.model;

import static java.util.Collections.unmodifiableList;

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

public class Gruppe {

	private final String name;
	private List<Eintrag> eintraege = new ArrayList<Eintrag>();

	public Gruppe(String name) {
		this.name = name;
	}

	public String getName() {
		return name;
	}

	public void addEintrag(Eintrag eintrag) {
		Gruppe alteGruppe = eintrag.getGruppe();
		if (alteGruppe != null) {
			alteGruppe.removeEintrag(eintrag);
		}
		eintraege.add(eintrag);
		eintrag.setGruppe(this);
	}

	private void removeEintrag(Eintrag eintrag) {
		eintraege.remove(eintrag);
		eintrag.resetGruppe();
	}

	@Override
	public String toString() {
		return name;
	}

	public List<Eintrag> getEintraege() {
		return unmodifiableList(eintraege);
	}

	public void addEintraege(Iterable<Eintrag> eintraege) {
		for (Eintrag eintrag : eintraege) {
			addEintrag(eintrag);
		}
	}

}

Model.java

package de.marcphilipp.dnd.model;

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

public enum Model {
	INSTANCE;
	
	List<Gruppe> gruppen = new ArrayList<Gruppe>();
	
	private Model() {
		Gruppe gruppe1 = new Gruppe("Gruppe 1");
		gruppe1.addEintrag(new Eintrag("short"));
		gruppen.add(gruppe1);
		Gruppe gruppe2 = new Gruppe("Gruppe 2");
		gruppe2.addEintrag(new Eintrag("short2"));
		gruppen.add(gruppe2);
	}
	
	public List<Gruppe> getModel(){
		return gruppen;
	}
}

MyDragListener.java

package de.marcphilipp.dnd.view;

import org.eclipse.jface.util.LocalSelectionTransfer;
import org.eclipse.jface.viewers.ISelectionProvider;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;

public class MyDragListener extends DragSourceAdapter {

	private final ISelectionProvider selectionProvider;

	public MyDragListener(ISelectionProvider selectionProvider) {
		this.selectionProvider = selectionProvider;
	}

	@Override
	public void dragSetData(DragSourceEvent event) {
		IStructuredSelection selection = (IStructuredSelection) selectionProvider
				.getSelection();

		LocalSelectionTransfer transfer = LocalSelectionTransfer.getTransfer();
		if (transfer.isSupportedType(event.dataType)) {
			transfer.setSelection(selection);
			transfer.setSelectionSetTime(event.time & 0xFFFF);
		}
	}

}

MyDropListener.java

package de.marcphilipp.dnd.view;

import java.util.List;

import org.eclipse.jface.util.LocalSelectionTransfer;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerDropAdapter;
import org.eclipse.swt.dnd.TransferData;

import de.marcphilipp.dnd.model.Eintrag;
import de.marcphilipp.dnd.model.Gruppe;

public class MyDropListener extends ViewerDropAdapter {

	public MyDropListener(Viewer viewer) {
		super(viewer);
	}

	@Override
	public boolean validateDrop(Object target, int operation,
			TransferData transferType) {
		return getCurrentLocation() == LOCATION_ON
				&& target instanceof Gruppe
				&& LocalSelectionTransfer.getTransfer().isSupportedType(
						transferType);
	}

	@Override
	public boolean performDrop(Object data) {
		List<Eintrag> eintraege = ermittleEintraege();
		Gruppe gruppe = (Gruppe) getCurrentTarget();
		gruppe.addEintraege(eintraege);
		getViewer().refresh();
		return true;
	}

	@SuppressWarnings("unchecked")
	private List<Eintrag> ermittleEintraege() {
		LocalSelectionTransfer transfer = LocalSelectionTransfer.getTransfer();
		IStructuredSelection selection = (IStructuredSelection) transfer.getSelection();
		return (List<Eintrag>) selection.toList();
	}

}

TreeContentProvider.java

package de.marcphilipp.dnd.view;

import java.util.List;

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

import de.marcphilipp.dnd.model.Eintrag;
import de.marcphilipp.dnd.model.Gruppe;

public class TreeContentProvider implements ITreeContentProvider {

	@Override
	public Object[] getChildren(Object parentElement) {
		return ((Gruppe) parentElement).getEintraege().toArray();
	}

	@Override
	public Object getParent(Object element) {
		return ((Eintrag)element).getGruppe();
	}

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

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

	@Override
	public void dispose() {
		
	}

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

}

TreeView.java

package de.marcphilipp.dnd.view;

import static org.eclipse.swt.dnd.DND.DROP_MOVE;

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

import de.marcphilipp.dnd.model.Model;

public class TreeView extends ViewPart {

	@Override
	public void createPartControl(Composite parent) {
		TreeViewer viewer = new TreeViewer(parent, SWT.MULTI | SWT.H_SCROLL
				| SWT.V_SCROLL);
		Transfer[] transferTypes = { LocalSelectionTransfer.getTransfer() };
		viewer.addDragSupport(DROP_MOVE, transferTypes, new MyDragListener(
				viewer));
		viewer.addDropSupport(DROP_MOVE, transferTypes, new MyDropListener(
				viewer));
		viewer.setContentProvider(new TreeContentProvider());
		viewer.setInput(Model.INSTANCE.getModel());
	}

	@Override
	public void setFocus() {
	}

}