ResourceTransferHandler.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package bradswebdavclient;

import java.awt.*;
import java.awt.datatransfer.Clipboard;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import javax.swing.JComponent;
import javax.swing.tree.*;
import java.awt.dnd.*;
import java.awt.event.InputEvent;
import javax.swing.TransferHandler;

public abstract class ResourceTransferHandler extends TransferHandler implements Unloadable {

    protected final JComponent component;
    protected final DragSource dragSource;
    protected final DropTarget dt;

    protected abstract TransferableResourceList selectedResources();

    protected abstract boolean canPerformAction(JComponent target, Transferable transferable, int action, Point location);

    protected abstract boolean executeDrop(Transferable transferable, Point pt, int action);

    ResourceTransferHandler(JComponent component) {
        this.component = component;
        component.setTransferHandler(this);
        dragSource = new DragSource();
        dragSource.createDefaultDragGestureRecognizer(component, DnDConstants.ACTION_COPY_OR_MOVE, new ResourceDragGestureListener());
        dt = new DropTarget(component, new ResourceDropTargetListener());
        component.setDropTarget(dt);
    }

    public void unload() {
        component.setTransferHandler(null);
        component.setDropTarget(null);
    }

    @Override
    public boolean canImport(JComponent comp, DataFlavor[] transferFlavors) {
        boolean b = super.canImport(comp, transferFlavors);
        System.out.println("canImport: " + b);
        return b;
    }

    @Override
    public void exportAsDrag(JComponent comp, InputEvent e, int action) {
        System.out.println("export as drag");
        super.exportAsDrag(comp, e, action);
    }

    @Override
    public void exportToClipboard(JComponent comp, Clipboard clip, int action) throws IllegalStateException {
        super.exportToClipboard(comp, clip, action);
    }

    @Override
    protected Transferable createTransferable(JComponent c) {
        return selectedResources();
    }

    class ResourceDragSourceListener implements DragSourceListener {

        public void dragDropEnd(DragSourceDropEvent dsde) {
        }

        public final void dragEnter(DragSourceDragEvent dsde) {
            int action = dsde.getDropAction();
            if (action == DnDConstants.ACTION_COPY) {
                dsde.getDragSourceContext().setCursor(DragSource.DefaultCopyDrop);
            } else {
                if (action == DnDConstants.ACTION_MOVE) {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
                } else {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
                }
            }
        }

        public final void dragOver(DragSourceDragEvent dsde) {
            int action = dsde.getDropAction();
            if (action == DnDConstants.ACTION_COPY) {
                dsde.getDragSourceContext().setCursor(DragSource.DefaultCopyDrop);
            } else {
                if (action == DnDConstants.ACTION_MOVE) {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
                } else {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
                }
            }
        }

        public final void dropActionChanged(DragSourceDragEvent dsde) {
            int action = dsde.getDropAction();
            if (action == DnDConstants.ACTION_COPY) {
                dsde.getDragSourceContext().setCursor(DragSource.DefaultCopyDrop);
            } else {
                if (action == DnDConstants.ACTION_MOVE) {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveDrop);
                } else {
                    dsde.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
                }
            }
        }

        public final void dragExit(DragSourceEvent dse) {
            dse.getDragSourceContext().setCursor(DragSource.DefaultMoveNoDrop);
        }

        public boolean executeDrop(final Transferable transferable, final Droppable droppable, final int action) {
            if (action == DnDConstants.ACTION_COPY) {
                return droppable.acceptCopyDrop(transferable);
            } else if (action == DnDConstants.ACTION_MOVE) {
                return droppable.acceptMoveDrop(transferable);
            } else {
                return false;
            }
        }
    }

    class ResourceDropTargetListener implements DropTargetListener {

        public final void dragEnter(DropTargetDragEvent dtde) {
            int action = dtde.getDropAction();
            dtde.acceptDrag(action);
        }

        public final void dragExit(DropTargetEvent dte) {
        }

        public final void dragOver(DropTargetDragEvent dtde) {
            Point pt = dtde.getLocation();
            int action = dtde.getDropAction();
            if (canPerformAction(component, dtde.getTransferable(), action, pt)) {
                dtde.acceptDrag(action);
            } else {
                dtde.rejectDrag();
            }
        }

        public final void dropActionChanged(DropTargetDragEvent dtde) {
            Point pt = dtde.getLocation();
            int action = dtde.getDropAction();
            if (canPerformAction(component, dtde.getTransferable(), action, pt)) {
                dtde.acceptDrag(action);
            } else {
                dtde.rejectDrag();
            }
        }

        public final void drop(DropTargetDropEvent dtde) {
            System.out.println("drop");
            try {
                int action = dtde.getDropAction();
                Transferable transferable = dtde.getTransferable();
                Point pt = dtde.getLocation();
                if (executeDrop(transferable, pt, action)) {
                    dtde.acceptDrop(action);
                    dtde.dropComplete(true);
                    return;
                }
            } catch (Exception e) {
                System.out.println(e);
                dtde.rejectDrop();
                dtde.dropComplete(false);
            }
        }
    }

    class ResourceDragGestureListener implements DragGestureListener {

        public final void dragGestureRecognized(DragGestureEvent dge) {
            TransferableResourceList resources = selectedResources();
            System.out.println("dragGestureRecognized: " + resources);
            if (resources != null && resources.size() > 0) {
                dragSource.startDrag(dge, DragSource.DefaultMoveNoDrop, resources, new ResourceDragSourceListener());
            }
        }
    }
}