AbstractViewerDropAdapter.java

package org.bndtools.utils.dnd;

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

import org.eclipse.core.resources.IResource;
import org.eclipse.jface.util.LocalSelectionTransfer;
import org.eclipse.jface.viewers.ISelection;
import org.eclipse.jface.viewers.StructuredViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.jface.viewers.ViewerDropAdapter;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DropTargetEvent;
import org.eclipse.swt.dnd.FileTransfer;
import org.eclipse.swt.dnd.TextTransfer;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.dnd.TransferData;
import org.eclipse.ui.part.ResourceTransfer;

public class AbstractViewerDropAdapter extends ViewerDropAdapter {

    private final EnumSet<SupportedTransfer> supportedTransfers;

    public AbstractViewerDropAdapter(Viewer viewer, EnumSet<SupportedTransfer> supportedTransfers) {
        super(viewer);
        this.supportedTransfers = supportedTransfers;
    }

    public void install(StructuredViewer viewer) {
        List<Transfer> transfers = new ArrayList<Transfer>();

        if (supportedTransfers.contains(SupportedTransfer.File))
            transfers.add(FileTransfer.getInstance());
        if (supportedTransfers.contains(SupportedTransfer.Resource))
            transfers.add(ResourceTransfer.getInstance());
        if (supportedTransfers.contains(SupportedTransfer.Text))
            transfers.add(TextTransfer.getInstance());
        if (supportedTransfers.contains(SupportedTransfer.LocalSelection))
            transfers.add(LocalSelectionTransfer.getTransfer());

        viewer.addDropSupport(DND.DROP_COPY | DND.DROP_MOVE, transfers.toArray(new Transfer[0]), this);
    }

    // Turn all move events into copy events
    @Override
    public void dragEnter(DropTargetEvent event) {
        super.dragEnter(event);
        event.detail = DND.DROP_COPY;
    }

    @Override
    public boolean performDrop(Object data) {
        Object target = getCurrentTarget();
        int location = getCurrentLocation();

        boolean result = false;
        if (data instanceof String) {
            result = performTextDrop((String) data, target, location);
        } else if (data instanceof String[]) {
            result = performFileDrop((String[]) data, target, location);
        } else if (data instanceof IResource[]) {
            result = performResourceDrop((IResource[]) data, target, location);
        } else if (data instanceof ISelection) {
            result = performSelectionDrop((ISelection) data, target, location);
        }
        return result;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean performTextDrop(String data, Object target, int location) {
        return false;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean performFileDrop(String[] data, Object target, int location) {
        return false;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean performResourceDrop(IResource[] data, Object target, int location) {
        return false;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean performSelectionDrop(ISelection data, Object target, int location) {
        return false;
    }

    @Override
    public boolean validateDrop(Object target, int operation, TransferData transferType) {
        if (supportedTransfers.contains(SupportedTransfer.File) && FileTransfer.getInstance().isSupportedType(transferType)) {
            return validateFileDrop(target);
        } else if (supportedTransfers.contains(SupportedTransfer.Resource) && ResourceTransfer.getInstance().isSupportedType(transferType)) {
            return validateResourceDrop(target);
        } else if (supportedTransfers.contains(SupportedTransfer.Text) && TextTransfer.getInstance().isSupportedType(transferType)) {
            return validateTextDrop(target);
        } else if (supportedTransfers.contains(SupportedTransfer.LocalSelection) && LocalSelectionTransfer.getTransfer().isSupportedType(transferType)) {
            return validateLocalSelectionDrop(target);
        } else {
            return false;
        }
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean validateFileDrop(Object target) {
        return true;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean validateResourceDrop(Object target) {
        return true;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean validateTextDrop(Object target) {
        return true;
    }

    @SuppressWarnings({
            "static-method", "unused"
    })
    protected boolean validateLocalSelectionDrop(Object target) {
        return true;
    }

}