ITEEDU

10-7:JTree的事件处理模式:

在此节中，我们将详细介绍JTree两个常用的事件与处理，分别是TreeModeEvent与TreeSelectionEvent. 10-7-1:处理TreeModeEvent事件：

当树的结构上有任何改变时，例如节点值改变了、新增节点、删除节点等，都会TreeModelEvent事件，要处理这样的事件必须实 作TreeModelListener界面，此界面定义了4个方法，如下所示:

TreeModelListener方法:

• Void treeNodesChanged(TreeModelEvent e):当节点改变时系统就会云调用这个方法。
• Void treeNodesInserted(TreeModelEvent e):当新增节时系统就会去调用这个方法。
• Void treeNodesRemoved(TreeModeEvent e):当删除节点时系统就会去调用这个方法。
• Void treeStructureChanged(TreeModelEvent e):当树结构改变时系统就会去调用这个方法。

TreeModelEvent类本身提供了5个方法，帮我们取得事件的信息，如下所示:

TreeModelEvent方法：

• int[] getChildIndices():返回子节点群的索引值。
• Object[] getChildren():返回子节点群.
• Object[] getPath():返回Tree中一条path上(从root nod到leaf node)的节点。
• TreePath getTreePath():取得目前位置的Tree Path.
• String toString()：取得蝗字符串表示法.

由TreeModelEvent的getTreePath()方法就可以得到TreePath对象，此对象就能够让我们知道用户目前正选哪一个节点， TreePath类最常用的方法为：

• public Object getLastPathComponent():取得最深（内）层的节点。
• public int getPathCount():取得此path上共有几个节点.

我们来看下面这个例子，用户可以在Tree上编辑节点，按下[Enter]键后就可以改变原有的值，并将改变的值显示在下面的 JLabel中:

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import com.incors.plaf.alloy.*;
import com.incors.plaf.alloy.themes.bedouin.*;

public class TreeDemo5 implements TreeModelListener {
	JLabel label = null;
	String nodeName = null; // 原有节点名称

	public TreeDemo5() {
		try {
			AlloyLookAndFeel.setProperty("alloy.isLookAndFeelFrameDecoration",
					"true");
			AlloyTheme theme = new BedouinTheme();// 设置界面的外观，手册中共有5种样式
			LookAndFeel alloyLnF = new AlloyLookAndFeel(theme);
			UIManager.setLookAndFeel(alloyLnF);
		} catch (UnsupportedLookAndFeelException ex) {
			// You may handle the exception here
		}
		// this line needs to be implemented in order to make JWS work properly
		UIManager.getLookAndFeelDefaults().put("ClassLoader",
				getClass().getClassLoader());
		JFrame f = new JFrame("TreeDemo");
		Container contentPane = f.getContentPane();

		DefaultMutableTreeNode root = new DefaultMutableTreeNode("资源管理器");
		DefaultMutableTreeNode node1 = new DefaultMutableTreeNode("文件夹");
		DefaultMutableTreeNode node2 = new DefaultMutableTreeNode("我的电脑");
		DefaultMutableTreeNode node3 = new DefaultMutableTreeNode("收藏夹");
		DefaultMutableTreeNode node4 = new DefaultMutableTreeNode("Readme");
		root.add(node1);
		root.add(node2);
		root.add(node3);
		root.add(node4);

		DefaultMutableTreeNode leafnode = new DefaultMutableTreeNode("公司文件");
		node1.add(leafnode);
		leafnode = new DefaultMutableTreeNode("个人信件");
		node1.add(leafnode);
		leafnode = new DefaultMutableTreeNode("私人文件");
		node1.add(leafnode);

		leafnode = new DefaultMutableTreeNode("本机磁盘(C:)");
		node2.add(leafnode);
		leafnode = new DefaultMutableTreeNode("本机磁盘(D:)");
		node2.add(leafnode);
		leafnode = new DefaultMutableTreeNode("本机磁盘(E:)");
		node2.add(leafnode);

		DefaultMutableTreeNode node31 = new DefaultMutableTreeNode("网站列表");
		node3.add(node31);

		leafnode = new DefaultMutableTreeNode("天勤网站");
		node31.add(leafnode);
		leafnode = new DefaultMutableTreeNode("足球消息");
		node31.add(leafnode);
		leafnode = new DefaultMutableTreeNode("网络书店");
		node31.add(leafnode);

		JTree tree = new JTree(root);
		tree.setEditable(true);// 设置JTree为可编辑的
		tree.addMouseListener(new MouseHandle());// 使Tree加入检测Mouse事件，以便取得节点名称
		// 下面两行取得DefaultTreeModel,并检测是否有TreeModelEvent事件.
		DefaultTreeModel treeModel = (DefaultTreeModel) tree.getModel();
		treeModel.addTreeModelListener(this);

		JScrollPane scrollPane = new JScrollPane();
		scrollPane.setViewportView(tree);

		label = new JLabel("更改数据为: ");
		contentPane.add(scrollPane, BorderLayout.CENTER);
		contentPane.add(label, BorderLayout.SOUTH);
		f.pack();
		f.setVisible(true);

		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});

	}

	/*
	 * 本方法实作TreeModelListener接口，本接口共定义四个方法，分别是TreeNodesChanged()
	 * treeNodesInserted()、treeNodesRemoved()、treeNodesRemoved()、
	 * treeStructureChanged().在此范例中我们只针对更改节点值的部份，因此只实作treeNodesChanged()方法.
	 */
	public void treeNodesChanged(TreeModelEvent e) {

		TreePath treePath = e.getTreePath();
		System.out.println(treePath);
		// 下面这行由TreeModelEvent取得的DefaultMutableTreeNode为节点的父节点，而不是用户点选
		// 的节点，这点读者要特别注意。要取得真正的节点需要再加写下面6行代码.
		DefaultMutableTreeNode node = (DefaultMutableTreeNode) treePath
				.getLastPathComponent();
		try {
			// getChildIndices()方法会返回目前修改节点的索引值。由于我们只修改一个节点，因此节点索引值就放在index[0]
			// 的位置，若点选的节点为root
			// node,则getChildIndices()的返回值为null,程序下面的第二行就在处理点选root
			// node产生的NullPointerException问题.
			int[] index = e.getChildIndices();
			// 由DefaultMutableTreeNode类的getChildAt()方法取得修改的节点对象.
			node = (DefaultMutableTreeNode) node.getChildAt(index[0]);
		} catch (NullPointerException exc) {
		}
		// 由DefaultMutableTreeNode类getUserObject()方法取得节点的内容，或是写成node.toString()亦相同.
		label.setText(nodeName + "更改数据为: " + (String) node.getUserObject());
	}

	public void treeNodesInserted(TreeModelEvent e) {
	}

	public void treeNodesRemoved(TreeModelEvent e) {
	}

	public void treeStructureChanged(TreeModelEvent e) {
	}

	public static void main(String args[]) {

		new TreeDemo5();
	}

	// 处理Mouse点选事件
	class MouseHandle extends MouseAdapter {
		public void mousePressed(MouseEvent e) {
			try {
				JTree tree = (JTree) e.getSource();
				// JTree的getRowForLocation()方法会返回节点的列索引值。例如本例中，“本机磁盘(D:)”的列索引值为4,此索引值
				// 会随着其他数据夹的打开或收起而变支，但“资源管理器”的列索引值恒为0.
				int rowLocation = tree.getRowForLocation(e.getX(), e.getY());

				/*
				 * JTree的getPathForRow()方法会取得从root
				 * node到点选节点的一条path,此path为一条直线，如程序运行的图示若你点选“本机磁盘(E:)”,则Tree
				 * Path为"资源管理器"-->"我的电脑"-->"本机磁盘(E:)",因此利用TreePath
				 * 的getLastPathComponent()方法就可以取得所点选的节点.
				 */

				TreePath treepath = tree.getPathForRow(rowLocation);
				TreeNode treenode = (TreeNode) treepath.getLastPathComponent();

				nodeName = treenode.toString();
			} catch (NullPointerException ne) {
			}
		}
	}
}

注:上面的程序MouseHandle中:

 int rowLocation = tree.getRowForLocation(e.getX(), e.getY());
    TreePath treepath = tree.getPathForRow(rowLocation);

与：TreePath treepath=tree.getSelectionPath(); 等价，可互换。

我们将“我的电脑”改成“网上领居”:

我们再来看一个TreeModelEvent的例子，下面这个例子我们可以让用户自行增加、删除与修改节点：

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;
import com.incors.plaf.alloy.*;
import com.incors.plaf.alloy.themes.bedouin.*;

public class TreeDemo6 implements ActionListener, TreeModelListener {
	JLabel label = null;
	JTree tree = null;
	DefaultTreeModel treeModel = null;
	String nodeName = null;// 原有节点名称

	public TreeDemo6() {
		try {
			AlloyLookAndFeel.setProperty("alloy.isLookAndFeelFrameDecoration",
					"true");
			AlloyTheme theme = new BedouinTheme();
			LookAndFeel alloyLnF = new AlloyLookAndFeel(theme);
			UIManager.setLookAndFeel(alloyLnF);
		} catch (UnsupportedLookAndFeelException ex) {
			// You may handle the exception here
		}
		// this line needs to be implemented in order to make JWS work properly
		UIManager.getLookAndFeelDefaults().put("ClassLoader",
				getClass().getClassLoader());
		JFrame f = new JFrame("TreeDemo6");
		Container contentPane = f.getContentPane();

		DefaultMutableTreeNode root = new DefaultMutableTreeNode("资源管理器");

		tree = new JTree(root);
		tree.setEditable(true);
		tree.addMouseListener(new MouseHandle());
		treeModel = (DefaultTreeModel) tree.getModel();
		treeModel.addTreeModelListener(this);

		JScrollPane scrollPane = new JScrollPane();
		scrollPane.setViewportView(tree);

		JPanel panel = new JPanel();
		JButton b = new JButton("新增节点");
		b.addActionListener(this);
		panel.add(b);
		b = new JButton("删除节点");
		b.addActionListener(this);
		panel.add(b);
		b = new JButton("清除所有节点");
		b.addActionListener(this);
		panel.add(b);

		label = new JLabel("Action");
		contentPane.add(panel, BorderLayout.NORTH);
		contentPane.add(scrollPane, BorderLayout.CENTER);
		contentPane.add(label, BorderLayout.SOUTH);
		f.pack();
		f.setVisible(true);
		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	}

	// 本方法运行新增、删除、清除所有节点的程序代码.
	public void actionPerformed(ActionEvent ae) {
		if (ae.getActionCommand().equals("新增节点")) {
			DefaultMutableTreeNode parentNode = null;
			DefaultMutableTreeNode newNode = new DefaultMutableTreeNode("新节点");
			newNode.setAllowsChildren(true);
			TreePath parentPath = tree.getSelectionPath();

			// 取得新节点的父节点
			parentNode = (DefaultMutableTreeNode) (parentPath
					.getLastPathComponent());

			// 由DefaultTreeModel的insertNodeInto（）方法增加新节点
			treeModel.insertNodeInto(newNode, parentNode, parentNode
					.getChildCount());

			// tree的scrollPathToVisible()方法在使Tree会自动展开文件夹以便显示所加入的新节点。若没加这行则加入的新节点
			// 会被 包在文件夹中，你必须自行展开文件夹才看得到。
			tree.scrollPathToVisible(new TreePath(newNode.getPath()));
			label.setText("新增节点成功");
		}
		if (ae.getActionCommand().equals("删除节点")) {
			TreePath treepath = tree.getSelectionPath();
			if (treepath != null) {
				// 下面两行取得选取节点的父节点.
				DefaultMutableTreeNode selectionNode = (DefaultMutableTreeNode) treepath
						.getLastPathComponent();
				TreeNode parent = (TreeNode) selectionNode.getParent();
				if (parent != null) {
					// 由DefaultTreeModel的removeNodeFromParent()方法删除节点，包含它的子节点。
					treeModel.removeNodeFromParent(selectionNode);
					label.setText("删除节点成功");
				}
			}
		}
		if (ae.getActionCommand().equals("清除所有节点")) {

			// 下面一行，由DefaultTreeModel的getRoot()方法取得根节点.
			DefaultMutableTreeNode rootNode = (DefaultMutableTreeNode) treeModel
					.getRoot();

			// 下面一行删除所有子节点.
			rootNode.removeAllChildren();

			// 删除完后务必运行DefaultTreeModel的reload()操作，整个Tree的节点才会真正被删除.
			treeModel.reload();
			label.setText("清除所有节点成功");
		}
	}

	public void treeNodesChanged(TreeModelEvent e) {
		TreePath treePath = e.getTreePath();
		DefaultMutableTreeNode node = (DefaultMutableTreeNode) treePath
				.getLastPathComponent();
		try {
			int[] index = e.getChildIndices();
			node = (DefaultMutableTreeNode) node.getChildAt(index[0]);
		} catch (NullPointerException exc) {
		}
		label.setText(nodeName + "更改数据为:" + (String) node.getUserObject());
	}

	public void treeNodesInserted(TreeModelEvent e) {
		System.out.println("new node insered");
	}

	public void treeNodesRemoved(TreeModelEvent e) {
		System.out.println("node deleted");
	}

	public void treeStructureChanged(TreeModelEvent e) {
		System.out.println("Structrue changed");
	}

	public static void main(String[] args) {
		new TreeDemo6();
	}

	class MouseHandle extends MouseAdapter {
		public void mousePressed(MouseEvent e) {
			try {
				JTree tree = (JTree) e.getSource();
				int rowLocation = tree.getRowForLocation(e.getX(), e.getY());
				TreePath treepath = tree.getPathForRow(rowLocation);
				TreeNode treenode = (TreeNode) treepath.getLastPathComponent();
				nodeName = treenode.toString();
			} catch (NullPointerException ne) {
			}
		}
	}
}