net.husoftware.client.spike.DragDropLabel.java Source code

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Here is the source code for net.husoftware.client.spike.DragDropLabel.java

Source

package net.husoftware.client.spike;

/* This file is part of "DragDropTree".
    
 "DragDropTree" is free software: you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.
    
 "DragDropTree" is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
    
 You should have received a copy of the GNU General Public License
 along with "DragDropTree".  If not, see <http://www.gnu.org/licenses/>.
 */

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

import com.google.gwt.dom.client.Element;
import com.google.gwt.event.dom.client.DragLeaveEvent;
import com.google.gwt.event.dom.client.DragLeaveHandler;
import com.google.gwt.event.dom.client.DragOverEvent;
import com.google.gwt.event.dom.client.DragOverHandler;
import com.google.gwt.event.dom.client.DragStartEvent;
import com.google.gwt.event.dom.client.DragStartHandler;
import com.google.gwt.event.dom.client.DropEvent;
import com.google.gwt.event.dom.client.DropHandler;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.Tree;
import com.google.gwt.user.client.ui.TreeItem;
import com.google.gwt.user.client.ui.Widget;

public class DragDropLabel extends Label {
    private static DragDropLabel dragging = null;

    final boolean droppable;

    public DragDropLabel(String text, boolean draggable, boolean droppable) {
        super(text);
        if (draggable) {
            initDrag();
        }
        if (droppable) {
            initDrop();
        }
        this.droppable = droppable;

        if (droppable) {
            addStyleName("droppable");
        } else if (draggable) {
            addStyleName("draggable");
        }
    }

    private void initDrag() {
        getElement().setDraggable(Element.DRAGGABLE_TRUE);

        addDragStartHandler(new DragStartHandler() {
            @Override
            public void onDragStart(DragStartEvent event) {
                // Remember what's being dragged
                dragging = DragDropLabel.this;
                // Must set for FireFox
                event.setData("text", "hi there");

                // Copy the label image for the drag icon
                // 10,10 indicates the pointer offset, not the image size.
                event.getDataTransfer().setDragImage(getElement(), 10, 10);
            }
        });
    }

    private void initDrop() {
        addDomHandler(new DragOverHandler() {
            @Override
            public void onDragOver(DragOverEvent event) {
                addStyleName("dropping");
            }
        }, DragOverEvent.getType());

        addDomHandler(new DragLeaveHandler() {
            @Override
            public void onDragLeave(DragLeaveEvent event) {
                removeStyleName("dropping");
            }
        }, DragLeaveEvent.getType());

        addDomHandler(new DropHandler() {
            @Override
            public void onDrop(DropEvent event) {
                event.preventDefault();
                if (dragging != null) {
                    // Target treeitem is found via 'this';
                    // Dragged treeitem is found via 'dragging'.

                    TreeItem dragTarget = null;
                    TreeItem dragSource = null;

                    // The parent of 'this' is not the TreeItem, as that's not a Widget.
                    // The parent is the tree containing the treeitem.
                    Tree tree = (Tree) DragDropLabel.this.getParent();

                    // Visit the entire tree, searching for the drag and drop TreeItems

                    List<TreeItem> stack = new ArrayList<TreeItem>();
                    stack.add(tree.getItem(0));
                    while (!stack.isEmpty()) {
                        TreeItem item = stack.remove(0);
                        for (int i = 0; i < item.getChildCount(); i++) {
                            stack.add(item.getChild(i));
                        }

                        Widget w = item.getWidget();
                        if (w != null) {
                            if (w == dragging) {
                                dragSource = item;
                                if (dragTarget != null) {
                                    break;
                                }
                            }
                            if (w == DragDropLabel.this) {
                                dragTarget = item;
                                w.removeStyleName("dropping");
                                if (dragSource != null) {
                                    break;
                                }
                            }
                        }
                    }

                    // Do we have a source and a target?
                    if (dragSource != null && dragTarget != null) {
                        // Make sure that target is not a child of dragSource

                        TreeItem test = dragTarget;
                        while (test != null) {
                            if (test == dragSource) {
                                return;
                            }
                            test = test.getParentItem();
                        }

                        // Move the dragged item (source) under the target.
                        dragTarget.addItem(dragSource);
                        // Make sure the the target treeitem is open.
                        dragTarget.setState(true);
                    }
                    dragging = null;
                }
            }
        }, DropEvent.getType());
    }
}