JTree：如何檢查當前節點是否是文件

Question

我使用以下代碼填充一個完美的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
    }
}

給一個目錄字符串，它將該目錄中的所有文件添加到JTree，我的問題是我無法從每個節點獲取文件...我知道你可以使用

jtree.getLastSelectedPathComponent()

獲取最后選擇的組件，但我真正要檢查所選組件是否為File類型，如果是，返回該文件的路徑...有誰知道如何做到這一點？

Answer 1

您正在使用的DefaultMutableTreeNode包含一個'userObject'，在您的情況下是表示名稱的String ：

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

如果你想存儲File （一個或唯一標識符的節點File ），你可以使用檢索它提供吸氣 。

如果您選擇此方法，則可能必須更改樹上的渲染器。 可以通過擴展DefaultTreeCellRenderer並覆蓋getTreeCellRendererComponent來實現具有等效行為的渲染器，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：上面的代碼未經過測試。 我希望我的括號中沒有出現任何錯誤，...（懶得啟動我的IDE）

Answer 2

這是一個看起來或多或少與你相似的小片段（如果你能提供一個SSCCE會更容易）。 基本上，我將與DefaultMutableTreeNode關聯的用戶對象從String更改為File 。 我還添加了一個自定義的TreeCellRenderer來顯示File的名稱（而不是它的絕對路徑），以及一個TreeSelectionListener ，它向控制台輸出當前選定的File對象。

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();
            }
        });
    }
}

您可能還想查看此文件瀏覽器GUI 。

Answer 3

我正在使用這樣的東西：

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

    return node.getUserObject() instanceof MyNodeObject;
}

MyNodeObject應該與文件夾數據類型不同，因此您可以識別節點是否是文件。