本文介绍了在JTree中拖放节点的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
我无法创建一个JTree，允许通过在JTree中拖放来重新组织节点。这似乎应该比较简单。我已经在网上查看了例子，但是我似乎无法在我自己的代码中实现它。
I am having difficulty creating a JTree that allows the nodes to be reorganized by dragging and dropping them in the JTree. This seems like it should be relatively simple. I have looked at examples online, but I can not seem to implement it in my own code.
例如，允许在不同的组件之间拖动到树中，而不是从树内部拖动。
For example, this provided by sun allows for dragging between different components into the tree, but not from within the tree itself.
而且我也发现这样可以将文本拖到JTree中，但不在树中。
And I have also found this that allows you to drag text into the JTree, but not within the tree.
import java.awt.*;
import java.awt.datatransfer.*;
import java.awt.event.*;
import java.io.*;
import javax.swing.*;
import javax.swing.tree.*;
public class DndTree {
public static void main(String args[]) {
Runnable runner = new Runnable() {
public void run() {
JFrame f = new JFrame("D-n-D JTree");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
JPanel top = new JPanel(new BorderLayout());
JLabel dragLabel = new JLabel("Drag me:");
JTextField text = new JTextField();
text.setDragEnabled(true);
top.add(dragLabel, BorderLayout.WEST);
top.add(text, BorderLayout.CENTER);
f.add(top, BorderLayout.NORTH);
final JTree tree = new JTree();
final DefaultTreeModel model = (DefaultTreeModel) tree.getModel();
tree.setTransferHandler(new TransferHandler() {
public boolean canImport(TransferHandler.TransferSupport support) {
if (!support.isDataFlavorSupported(DataFlavor.stringFlavor)
|| !support.isDrop()) {
return false;
}
JTree.DropLocation dropLocation =
(JTree.DropLocation) support.getDropLocation();
return dropLocation.getPath() != null;
}
public boolean importData(TransferHandler.TransferSupport support) {
if (!canImport(support)) {
return false;
}
JTree.DropLocation dropLocation =
(JTree.DropLocation) support.getDropLocation();
TreePath path = dropLocation.getPath();
Transferable transferable = support.getTransferable();
String transferData;
try {
transferData = (String) transferable.getTransferData(
DataFlavor.stringFlavor);
} catch (IOException e) {
return false;
} catch (UnsupportedFlavorException e) {
return false;
}
int childIndex = dropLocation.getChildIndex();
if (childIndex == -1) {
childIndex = model.getChildCount(path.getLastPathComponent());
}
DefaultMutableTreeNode newNode =
new DefaultMutableTreeNode(transferData);
DefaultMutableTreeNode parentNode =
(DefaultMutableTreeNode) path.getLastPathComponent();
model.insertNodeInto(newNode, parentNode, childIndex);
TreePath newPath = path.pathByAddingChild(newNode);
tree.makeVisible(newPath);
tree.scrollRectToVisible(tree.getPathBounds(newPath));
return true;
}
});
JScrollPane pane = new JScrollPane(tree);
f.add(pane, BorderLayout.CENTER);
JPanel bottom = new JPanel();
JLabel comboLabel = new JLabel("DropMode");
String options[] = {"USE_SELECTION",
"ON", "INSERT", "ON_OR_INSERT"
};
final DropMode mode[] = {DropMode.USE_SELECTION,
DropMode.ON, DropMode.INSERT, DropMode.ON_OR_INSERT};
final JComboBox combo = new JComboBox(options);
combo.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
int selectedIndex = combo.getSelectedIndex();
tree.setDropMode(mode[selectedIndex]);
}
});
bottom.add(comboLabel);
bottom.add(combo);
f.add(bottom, BorderLayout.SOUTH);
f.setSize(300, 400);
f.setVisible(true);
}
};
EventQueue.invokeLater(runner);
}
}
任何参考或建议都会很棒。感谢
Any references or suggestions would be great. Thanks
推荐答案
以前没有这样做，但是一个快速的谷歌搜索在这里提出了同样的问题：它有一个可以查看的工作实现。
Haven't done this before, but a quick google search turned up the same question here: http://www.coderanch.com/t/346509/GUI/java/JTree-drag-drop-inside-one it has a working implementation that you can look at.
以下是Craig Wood发布的相关代码：
Here is the relevant code that Craig Wood posted:
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 < selRows.length; i++) {
if(selRows[i] == dropRow) {
return false;
}
}
// Do not allow MOVE-action drops if a non-leaf node is
// selected unless all of its children are also selected.
int action = support.getDropAction();
if(action == MOVE) {
return haveCompleteNode(tree);
}
// Do not allow a non-leaf node to be copied to a level
// which is less than its source level.
TreePath dest = dl.getPath();
DefaultMutableTreeNode target =
(DefaultMutableTreeNode)dest.getLastPathComponent();
TreePath path = tree.getPathForRow(selRows[0]);
DefaultMutableTreeNode firstNode =
(DefaultMutableTreeNode)path.getLastPathComponent();
if(firstNode.getChildCount() > 0 &&
target.getLevel() < firstNode.getLevel()) {
return false;
}
return true;
}
private boolean haveCompleteNode(JTree tree) {
int[] selRows = tree.getSelectionRows();
TreePath path = tree.getPathForRow(selRows[0]);
DefaultMutableTreeNode first =
(DefaultMutableTreeNode)path.getLastPathComponent();
int childCount = first.getChildCount();
// first has children and no children are selected.
if(childCount > 0 && selRows.length == 1)
return false;
// first may have children.
for(int i = 1; i < selRows.length; i++) {
path = tree.getPathForRow(selRows[i]);
DefaultMutableTreeNode next =
(DefaultMutableTreeNode)path.getLastPathComponent();
if(first.isNodeChild(next)) {
// Found a child of first.
if(childCount > 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<DefaultMutableTreeNode> copies =
new ArrayList<DefaultMutableTreeNode>();
List<DefaultMutableTreeNode> toRemove =
new ArrayList<DefaultMutableTreeNode>();
DefaultMutableTreeNode node =
(DefaultMutableTreeNode)paths[0].getLastPathComponent();
DefaultMutableTreeNode copy = copy(node);
copies.add(copy);
toRemove.add(node);
for(int i = 1; i < paths.length; i++) {
DefaultMutableTreeNode next =
(DefaultMutableTreeNode)paths[i].getLastPathComponent();
// Do not allow higher level nodes to be added to list.
if(next.getLevel() < node.getLevel()) {
break;
} else if(next.getLevel() > 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 < nodesToRemove.length; i++) {
model.removeNodeFromParent(nodesToRemove[i]);
}
}
}
public int getSourceActions(JComponent c) {
return COPY_OR_MOVE;
}
public boolean importData(TransferHandler.TransferSupport support) {
if(!canImport(support)) {
return false;
}
// Extract transfer data.
DefaultMutableTreeNode[] nodes = null;
try {
Transferable t = support.getTransferable();
nodes = (DefaultMutableTreeNode[])t.getTransferData(nodesFlavor);
} catch(UnsupportedFlavorException ufe) {
System.out.println("UnsupportedFlavor: " + ufe.getMessage());
} catch(java.io.IOException ioe) {
System.out.println("I/O error: " + ioe.getMessage());
}
// Get drop location info.
JTree.DropLocation dl =
(JTree.DropLocation)support.getDropLocation();
int childIndex = dl.getChildIndex();
TreePath dest = dl.getPath();
DefaultMutableTreeNode parent =
(DefaultMutableTreeNode)dest.getLastPathComponent();
JTree tree = (JTree)support.getComponent();
DefaultTreeModel model = (DefaultTreeModel)tree.getModel();
// Configure for drop mode.
int index = childIndex; // DropMode.INSERT
if(childIndex == -1) { // DropMode.ON
index = parent.getChildCount();
}
// Add data to model.
for(int i = 0; i < nodes.length; i++) {
model.insertNodeInto(nodes[i], parent, index++);
}
return true;
}
public String toString() {
return getClass().getName();
}
public class NodesTransferable implements Transferable {
DefaultMutableTreeNode[] nodes;
public NodesTransferable(DefaultMutableTreeNode[] nodes) {
this.nodes = nodes;
}
public Object getTransferData(DataFlavor flavor)
throws UnsupportedFlavorException {
if(!isDataFlavorSupported(flavor))
throw new UnsupportedFlavorException(flavor);
return nodes;
}
public DataFlavor[] getTransferDataFlavors() {
return flavors;
}
public boolean isDataFlavorSupported(DataFlavor flavor) {
return nodesFlavor.equals(flavor);
}
}
}
这篇关于在JTree中拖放节点的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！