JTree：如何检查当前节点是否为文件

Question

我正在使用以下代码来填充一个运行良好的 JTree

File [] children = new File(directory).listFiles(); // list all the files in the directory
for (int i = 0; i < children.length; i++) { // loop through each
    DefaultMutableTreeNode node = new DefaultMutableTreeNode(children[i].getName());
    // only display the node if it isn't a folder, and if this is a recursive call
    if (children[i].isDirectory() && recursive) {
        parent.add(node); // add as a child node
        listAllFiles(children[i].getPath(), node, recursive); // call again for the subdirectory
    } else if (!children[i].isDirectory()){ // otherwise, if it isn't a directory
        parent.add(node); // add it as a node and do nothing else
    }
}

给出一个目录字符串，它将该目录中的所有文件添加到 JTree，我的问题是我无法从每个节点获取文件...我知道你可以使用

jtree.getLastSelectedPathComponent()

获取最后一个选择的组件，但我真正要检查的是选择的组件是否为File 类型，如果是，则返回该文件的路径...有人知道该怎么做吗？

Answer 1

我正在使用这样的东西：

private boolean isFileSelected()
{
    TreePath treePath = tree.getSelectionPath();
    Object lastPathComponent = treePath.getLastPathComponent();
    DefaultMutableTreeNode node = (DefaultMutableTreeNode) lastPathComponent;

    return node.getUserObject() instanceof MyNodeObject;
}

MyNodeObject 应该与文件夹数据类型不同，以便您可以识别节点是否为文件。

Answer 2

这是一个看起来或多或少像你的小sn-p（如果你能提供SSCCE会更容易）。基本上，我将与DefaultMutableTreeNode 关联的用户对象从String 更改为File。我还添加了一个自定义的TreeCellRenderer 以仅显示File 的名称（而不是其绝对路径），以及一个TreeSelectionListener 将当前选定的File 对象输出到控制台。

import java.awt.Component;
import java.io.File;

import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.event.TreeSelectionEvent;
import javax.swing.event.TreeSelectionListener;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;

public class TestTreeFile {

    protected void initUI() {
        JFrame frame = new JFrame(TestTreeFile.class.getSimpleName());
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        final JTree tree = new JTree(createTreeModel(new File(System.getProperty("user.dir")), true));
        tree.setCellRenderer(new DefaultTreeCellRenderer() {
            @Override
            public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row,
                    boolean hasFocus) {
                super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);
                if (value instanceof DefaultMutableTreeNode) {
                    DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
                    if (node.getUserObject() instanceof File) {
                        setText(((File) node.getUserObject()).getName());
                    }
                }
                return this;
            }
        });
        tree.getSelectionModel().addTreeSelectionListener(new TreeSelectionListener() {

            @Override
            public void valueChanged(TreeSelectionEvent e) {
                Object object = tree.getLastSelectedPathComponent();
                if (object instanceof DefaultMutableTreeNode) {
                    Object userObject = ((DefaultMutableTreeNode) object).getUserObject();
                    if (userObject instanceof File) {
                        File file = (File) userObject;
                        System.err.println("Selected file" + file.getAbsolutePath() + " Is directory? " + file.isDirectory());
                    }
                }
            }
        });
        JScrollPane pane = new JScrollPane(tree);
        frame.add(pane);
        frame.setSize(400, 600);
        frame.setVisible(true);
    }

    private DefaultMutableTreeNode createTreeModel(File file, boolean recursive) {
        DefaultMutableTreeNode node = new DefaultMutableTreeNode(file);
        if (file.isDirectory() && recursive) {
            File[] children = file.listFiles(); // list all the files in the directory
            if (children != null) {
                for (File f : children) { // loop through each
                    node.add(createTreeModel(f, recursive));
                }
            }
        }
        return node;
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new TestTreeFile().initUI();
            }
        });
    }
}

您可能还想看看这个File Browser GUI。

Answer 3

您使用的DefaultMutableTreeNode 包含一个“userObject”，在您的情况下是代表名称的String：

DefaultMutableTreeNode node = new DefaultMutableTreeNode(children[i].getName());

如果您要将File 存储在节点中（或File 的任何唯一标识符），您可以使用available getter 检索它。

如果您选择这种方法，您可能需要更改树上的渲染器。可以通过扩展DefaultTreeCellRenderer 并覆盖getTreeCellRendererComponent 来实现具有等效行为的渲染器，如下所示

@Override
public Component getTreeCellRendererComponent(JTree tree, Object value, boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus){
  Component result = super.getTreeCellRendererComponent( tree, value, sel, expanded, leaf, row, hasFocus );
  if ( value instanceof DefaultMutableTreeNode && ((DefaultMutableTreeNode)value).getUserObject() instanceof File ){
     ((JLabel)result).setText( (File)((DefaultMutableTreeNode)value).getUserObject()).getName() );
  }
}

注意：以上代码未经测试。我希望我没有在括号中犯任何错误，...（懒得启动我的 IDE）