JPalette.java example

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ptii-master
/*
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package diva.gui.toolbox;

import java.awt.datatransfer.StringSelection;
import java.awt.datatransfer.Transferable;
import java.awt.dnd.DnDConstants;
import java.awt.dnd.DragGestureEvent;
import java.awt.dnd.DragGestureListener;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceContext;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;
import java.awt.dnd.InvalidDnDOperationException;

import javax.swing.BoxLayout;
import javax.swing.Icon;
import javax.swing.JComponent;
import javax.swing.JLabel;
import javax.swing.JPanel;

/**
 * A "palette" of components that can be dragged onto another
 * JComponent.  The components in the palette have String data
 * associated with them, and this is what the drop target sees
 * when a drop is initiated by the user.
 *
 * @author Michael Shilman
 * @version $Id$
 */
public class JPalette extends JPanel {
    /**
     * Construct a new palette instance with a vertical grid layout.
     */
    public JPalette() {
        // FIXME - need a real layout.
        setLayout(new BoxLayout(this, BoxLayout.Y_AXIS));

        // TESTING
        testLabel("foo");
        testLabel("bar");
        testLabel("baz");
    }

    /**
     * Add an icon to the palette, that is associated with the
     */
    public void addIcon(Icon i, String data) {
        JLabel l = new JLabel(i);
        makeDraggable(l, data);
        add(l);
    }

    /**
     * Make the given component draggable; the given data string will
     * be the "dragged" object that is associated with the component.
     * This data is made available via the StringSelection class,
     * meaning that it will support "plain text" and "java string"
     * data flavors.
     */
    public void makeDraggable(JComponent c, String data) {
        final String dataHandle = data;
        final DragSourceListener dsl = new DragSourceListener() {
            public void dragDropEnd(DragSourceDropEvent dsde) {
            }

            public void dragEnter(DragSourceDragEvent dsde) {
                DragSourceContext context = dsde.getDragSourceContext();

                //intersection of the users selected action, and the
                //source and target actions
                int myaction = dsde.getDropAction();

                if ((myaction & DnDConstants.ACTION_COPY) != 0) {
                    context.setCursor(DragSource.DefaultCopyDrop);
                } else {
                    context.setCursor(DragSource.DefaultCopyNoDrop);
                }
            }

            public void dragExit(DragSourceEvent dse) {
            }

            public void dragOver(DragSourceDragEvent dsde) {
            }

            public void dropActionChanged(DragSourceDragEvent dsde) {
            }
        };

        final DragGestureListener dgl = new DragGestureListener() {
            public void dragGestureRecognized(DragGestureEvent e) {
                try {
                    // check to see if action is OK ...
                    Transferable transferable = new StringSelection(dataHandle);

                    //initial cursor, transferable, dsource listener
                    e
                            .startDrag(DragSource.DefaultCopyNoDrop,
                                    transferable, dsl);
                } catch (InvalidDnDOperationException idoe) {
                    System.err.println(idoe);
                }
            }
        };

        DragSource.getDefaultDragSource().createDefaultDragGestureRecognizer(c,
                DnDConstants.ACTION_COPY_OR_MOVE, dgl);
    }

    /**
     * Add a a label to the palette with the same string
     * as its associated data, for testing purposes.
     */
    public void testLabel(String s) {
        JLabel l = new JLabel(s);
        makeDraggable(l, s);
        add(l);
    }

    //public void removeIcon(Icon i) {...}
}