我有一个类结构如下：
DefaultMutableTreeNode
|_
BCStructure
|_
| Module
|_
| Section
|_
Page
模块，部分和页面是我在JTree中实际使用的内容。如果您运行下面的示例代码，拖放工作。请注意，它使用的是DefaultMutableTreeNodes。但是，如果我将代码放在我使用DefualtMutableTreeNode子类的真实应用程序中，它就不起作用。
在逐步完成代码时，我注意到了两个感兴趣的领域。首先是：
class TreeTransferHandler extends TransferHandler {
DataFlavor nodesFlavor;
DataFlavor[] flavors = new DataFlavor[1];
DefaultMutableTreeNode[] nodesToRemove;
public TreeTransferHandler() {
try {
String mimeType = DataFlavor.javaJVMLocalObjectMimeType
+ ";class=\""
+ javax.swing.tree.DefaultMutableTreeNode[].class.getName()
+ "\"";
nodesFlavor = new DataFlavor(mimeType);
flavors[0] = nodesFlavor;
} catch (ClassNotFoundException e) {
System.out.println("ClassNotFound: " + e.getMessage());
}
}
这是设置DataFlavor的地方。它将它设置为DefualtMutableTreeNode数组，我认为这是正确的，因为DefaultMutableTreeNode是我的节点的超类。但这是我认为问题可能存在的一个方面。
另一点是在调试此代码时，我得到了：
public DataFlavor[] getTransferDataFlavors() {
return flavors;
}
。我假设它返回一个不太受欢迎的DataFlavor。这就是为什么我认为DataFlavor有问题。是否有更多我需要做/修改才能使用子类？有什么想法或建议吗？
谢谢！
完整的示例代码：
import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.dnd.*;
import java.util.*;
import java.util.List;
import javax.swing.*;
import javax.swing.tree.*;
public class TreeDragAndDrop {
private JScrollPane getContent() {
JTree tree = new JTree();
tree.setDragEnabled(true);
tree.setDropMode(DropMode.ON_OR_INSERT);
tree.setTransferHandler(new TreeTransferHandler());
tree.getSelectionModel().setSelectionMode(
TreeSelectionModel.CONTIGUOUS_TREE_SELECTION);
expandTree(tree);
return new JScrollPane(tree);
}
private void expandTree(JTree tree) {
DefaultMutableTreeNode root =
(DefaultMutableTreeNode)tree.getModel().getRoot();
Enumeration e = root.breadthFirstEnumeration();
while(e.hasMoreElements()) {
DefaultMutableTreeNode node =
(DefaultMutableTreeNode)e.nextElement();
if(node.isLeaf()) continue;
int row = tree.getRowForPath(new TreePath(node.getPath()));
tree.expandRow(row);
}
}
public static void main(String[] args) {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.add(new TreeDragAndDrop().getContent());
f.setSize(400,400);
f.setLocation(200,200);
f.setVisible(true);
}
}
class TreeTransferHandler extends TransferHandler {
DataFlavor nodesFlavor;
DataFlavor[] flavors = new DataFlavor[1];
DefaultMutableTreeNode[] nodesToRemove;
public TreeTransferHandler() {
try {
String mimeType = DataFlavor.javaJVMLocalObjectMimeType +
";class=\"" +
javax.swing.tree.DefaultMutableTreeNode[].class.getName() +
"\"";
nodesFlavor = new DataFlavor(mimeType);
flavors[0] = nodesFlavor;
} catch(ClassNotFoundException e) {
System.out.println("ClassNotFound: " + e.getMessage());
}
}
public boolean canImport(TransferHandler.TransferSupport support) {
if(!support.isDrop()) {
return false;
}
support.setShowDropLocation(true);
if(!support.isDataFlavorSupported(nodesFlavor)) {
return false;
}
// Do not allow a drop on the drag source selections.
JTree.DropLocation dl =
(JTree.DropLocation)support.getDropLocation();
JTree tree = (JTree)support.getComponent();
int dropRow = tree.getRowForPath(dl.getPath());
int[] selRows = tree.getSelectionRows();
for(int i = 0; i 0 &&
target.getLevel() 0 && selRows.length == 1)
return false;
// first may have children.
for(int i = 1; i selRows.length-1) {
// Not all children of first are selected.
return false;
}
}
}
return true;
}
protected Transferable createTransferable(JComponent c) {
JTree tree = (JTree)c;
TreePath[] paths = tree.getSelectionPaths();
if(paths != null) {
// Make up a node array of copies for transfer and
// another for/of the nodes that will be removed in
// exportDone after a successful drop.
List copies =
new ArrayList();
List toRemove =
new ArrayList();
DefaultMutableTreeNode node =
(DefaultMutableTreeNode)paths[0].getLastPathComponent();
DefaultMutableTreeNode copy = copy(node);
copies.add(copy);
toRemove.add(node);
for(int i = 1; i node.getLevel()) { // child node
copy.add(copy(next));
// node already contains child
} else { // sibling
copies.add(copy(next));
toRemove.add(next);
}
}
DefaultMutableTreeNode[] nodes =
copies.toArray(new DefaultMutableTreeNode[copies.size()]);
nodesToRemove =
toRemove.toArray(new DefaultMutableTreeNode[toRemove.size()]);
return new NodesTransferable(nodes);
}
return null;
}
/** Defensive copy used in createTransferable. */
private DefaultMutableTreeNode copy(TreeNode node) {
return new DefaultMutableTreeNode(node);
}
protected void exportDone(JComponent source, Transferable data, int action) {
if((action & MOVE) == MOVE) {
JTree tree = (JTree)source;
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Remove nodes saved in nodesToRemove in createTransferable.
for(int i = 0; i
答案 0 :(得分：0)
如果你认为问题在于你是DefaultMutableTreeNode的子类，那么试着让你的DataFlavor成为一个Object数组，或者更好的是一个ArrayList：
DataFlavor.javaJVMLocalObjectMimeType + ";class=java.util.ArrayList"
这样您就可以将copies列表与您的可转让列表一起返回。也许它会避免这个问题。
这里有一个关于如何使用列表执行此操作的粗略概述：
import javax.swing.*;
import javax.swing.tree.*;
import java.awt.*;
import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.awt.datatransfer.UnsupportedFlavorException;
import java.io.IOException;
import java.util.*;
import java.util.List;
/**
* Author: Denis Tulskiy
* Date: 1/5/11
*/
public class Test extends JFrame {
class NodeA extends DefaultMutableTreeNode {
NodeA(Object userObject) {
super(userObject);
}
}
class NodeB extends DefaultMutableTreeNode {
NodeB(Object userObject) {
super(userObject);
}
}
class NodeC extends DefaultMutableTreeNode {
NodeC(Object userObject) {
super(userObject);
}
}
private static class MyTransferHandler extends TransferHandler {
@Override
public int getSourceActions(JComponent c) {
return MOVE;
}
@Override
protected Transferable createTransferable(JComponent c) {
JTree tree = (JTree) c;
ArrayList<TreeNode> nodes = new ArrayList<TreeNode>();
for (TreePath path : tree.getSelectionPaths()) {
DefaultMutableTreeNode component = (DefaultMutableTreeNode) path.getLastPathComponent();
nodes.add(component);
}
return new NodesTransferable(nodes);
}
@Override
public boolean canImport(TransferSupport support) {
return support.isDataFlavorSupported(NodesTransferable.getDataFlavor());
}
@Override
public boolean importData(TransferSupport support) {
if (!canImport(support)) {
return false;
}
JTree tree = (JTree) support.getComponent();
List<DefaultMutableTreeNode> data = null;
try {
data = (List<DefaultMutableTreeNode>) support.getTransferable().getTransferData(NodesTransferable.getDataFlavor());
} catch (UnsupportedFlavorException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
if (data != null) {
Point dropPoint = support.getDropLocation().getDropPoint();
TreePath path = tree.getPathForLocation(dropPoint.x, dropPoint.y);
DefaultMutableTreeNode parent = (DefaultMutableTreeNode) path.getLastPathComponent();
for (DefaultMutableTreeNode node : data) {
node.removeFromParent();
parent.add(node);
}
DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
model.reload();
}
return true;
}
}
static class NodesTransferable implements Transferable {
private static DataFlavor dataFlavor;
public static DataFlavor getDataFlavor() {
if (dataFlavor == null) {
try {
dataFlavor = new DataFlavor(DataFlavor.javaJVMLocalObjectMimeType + ";class=java.util.ArrayList");
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
}
return dataFlavor;
}
private java.util.List<TreeNode> nodes;
NodesTransferable(List<TreeNode> nodes) {
this.nodes = nodes;
}
@Override
public DataFlavor[] getTransferDataFlavors() {
return new DataFlavor[]{getDataFlavor()};
}
@Override
public boolean isDataFlavorSupported(DataFlavor flavor) {
return flavor.match(dataFlavor);
}
@Override
public Object getTransferData(DataFlavor flavor) throws UnsupportedFlavorException, IOException {
return nodes;
}
}
public Test() {
JTree tree = new JTree();
tree.setDragEnabled(true);
tree.setDropMode(DropMode.ON_OR_INSERT);
DefaultMutableTreeNode root = new DefaultMutableTreeNode("Root");
NodeA child = new NodeA("nodea");
root.add(child);
child.add(new NodeB("nodeb"));
child.add(new NodeC("nodec"));
tree.setModel(new DefaultTreeModel(root));
tree.setTransferHandler(new MyTransferHandler());
setLayout(new BorderLayout());
add(tree, BorderLayout.CENTER);
setSize(300, 400);
setLocationRelativeTo(null);
setDefaultCloseOperation(EXIT_ON_CLOSE);
}
public static void main(String[] args) {
new Test().setVisible(true);
}
}