DragDropList.java Source code

Introduction

Here is the source code for DragDropList.java

Source

import java.awt.datatransfer.DataFlavor;
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.DragGestureRecognizer;
import java.awt.dnd.DragSource;
import java.awt.dnd.DragSourceDragEvent;
import java.awt.dnd.DragSourceDropEvent;
import java.awt.dnd.DragSourceEvent;
import java.awt.dnd.DragSourceListener;

import javax.swing.DefaultListModel;
import javax.swing.DropMode;
import javax.swing.JFrame;
import javax.swing.JList;
import javax.swing.JScrollPane;
import javax.swing.TransferHandler;

public class DragDropList extends JList {
    DefaultListModel model;

    public DragDropList() {
        super(new DefaultListModel());
        model = (DefaultListModel) getModel();
        setDragEnabled(true);
        setDropMode(DropMode.INSERT);

        setTransferHandler(new MyListDropHandler(this));

        new MyDragListener(this);

        model.addElement("a");
        model.addElement("b");
        model.addElement("c");
    }

    public static void main(String[] a) {
        JFrame f = new JFrame();
        f.add(new JScrollPane(new DragDropList()));
        f.setSize(300, 300);
        f.setVisible(true);
    }
}

class MyDragListener implements DragSourceListener, DragGestureListener {
    DragDropList list;

    DragSource ds = new DragSource();

    public MyDragListener(DragDropList list) {
        this.list = list;
        DragGestureRecognizer dgr = ds.createDefaultDragGestureRecognizer(list, DnDConstants.ACTION_MOVE, this);

    }

    public void dragGestureRecognized(DragGestureEvent dge) {
        StringSelection transferable = new StringSelection(Integer.toString(list.getSelectedIndex()));
        ds.startDrag(dge, DragSource.DefaultCopyDrop, transferable, this);
    }

    public void dragEnter(DragSourceDragEvent dsde) {
    }

    public void dragExit(DragSourceEvent dse) {
    }

    public void dragOver(DragSourceDragEvent dsde) {
    }

    public void dragDropEnd(DragSourceDropEvent dsde) {
        if (dsde.getDropSuccess()) {
            System.out.println("Succeeded");
        } else {
            System.out.println("Failed");
        }
    }

    public void dropActionChanged(DragSourceDragEvent dsde) {
    }
}

class MyListDropHandler extends TransferHandler {
    DragDropList list;

    public MyListDropHandler(DragDropList list) {
        this.list = list;
    }

    public boolean canImport(TransferHandler.TransferSupport support) {
        if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)) {
            return false;
        }
        JList.DropLocation dl = (JList.DropLocation) support.getDropLocation();
        if (dl.getIndex() == -1) {
            return false;
        } else {
            return true;
        }
    }

    public boolean importData(TransferHandler.TransferSupport support) {
        if (!canImport(support)) {
            return false;
        }

        Transferable transferable = support.getTransferable();
        String indexString;
        try {
            indexString = (String) transferable.getTransferData(DataFlavor.stringFlavor);
        } catch (Exception e) {
            return false;
        }

        int index = Integer.parseInt(indexString);
        JList.DropLocation dl = (JList.DropLocation) support.getDropLocation();
        int dropTargetIndex = dl.getIndex();

        System.out.println(dropTargetIndex + " : ");
        System.out.println("inserted");
        return true;
    }
}