疯狂JAVA讲义---第十二章：Swing编程（七）JTree树

树这东西给用户的感觉极为方便，但给程序员带来很大的麻烦，它是swing中最麻烦的控件之一。树要弄的好非常麻烦，图标的美化，层次的划分，各种事件的处理。。。对于初学者来说，就不要太讲究样式，下面举个粗糙的例子，eg

public class SimpleJTree {JFrame jf = new JFrame("简单树");JTree tree;//定义几个初始节点DefaultMutableTreeNode root = new DefaultMutableTreeNode("中国"); DefaultMutableTreeNode guangdong = new DefaultMutableTreeNode("广东");DefaultMutableTreeNode guangxi = new DefaultMutableTreeNode("广西");DefaultMutableTreeNode foshan = new DefaultMutableTreeNode("佛山");DefaultMutableTreeNode shantou = new DefaultMutableTreeNode("汕头");DefaultMutableTreeNode guilin = new DefaultMutableTreeNode("桂林");DefaultMutableTreeNode nanning = new DefaultMutableTreeNode("南宁");public void init(){//通过add方法建立树节点之间的父子关系guangdong.add(foshan);guangdong.add(shantou);guangxi.add(guilin);guangxi.add(nanning);root.add(guangdong);root.add(guangxi);//以根节点创建树tree = new JTree(root);//默认连线//tree.putClientProperty("JTree.lineStyle" , "Angeled");//没有连线tree.putClientProperty("JTree.lineStyle" , "None");//水平分隔线//tree.putClientProperty("JTree.lineStyle" , "Horizontal"); //设置是否显示根节点的“展开/折叠”图标,默认是falsetree.setShowsRootHandles(true);//设置节点是否可见,默认是truetree.setRootVisible(true);jf.add(new JScrollPane(tree));jf.pack();jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);jf.setVisible(true);} public static void main(String[] args) {new SimpleJTree().init(); }}

拖动，编辑树节点也是树的基本功能，下面就在上面例子的基础上，加上这些功能，eg

 public class EditJTree{JFrame jf;JTree tree;//上面JTree对象对应的modelDefaultTreeModel model;//定义几个初始节点DefaultMutableTreeNode root = new DefaultMutableTreeNode("中国"); DefaultMutableTreeNode guangdong = new DefaultMutableTreeNode("广东");DefaultMutableTreeNode guangxi = new DefaultMutableTreeNode("广西");DefaultMutableTreeNode foshan = new DefaultMutableTreeNode("佛山");DefaultMutableTreeNode shantou = new DefaultMutableTreeNode("汕头");DefaultMutableTreeNode guilin = new DefaultMutableTreeNode("桂林");DefaultMutableTreeNode nanning = new DefaultMutableTreeNode("南宁");//定义需要被拖动的TreePathTreePath movePath; JButton addSiblingButton = new JButton("添加兄弟节点"); JButton addChildButton = new JButton("添加子节点"); JButton deleteButton = new JButton("删除节点"); JButton editButton = new JButton("编辑当前节点");public void init(){guangdong.add(foshan);guangdong.add(shantou);guangxi.add(guilin);guangxi.add(nanning);root.add(guangdong);root.add(guangxi);jf = new JFrame("树");tree = new JTree(root);//获取JTree对应的TreeModel对象model = (DefaultTreeModel)tree.getModel();//设置JTree可编辑tree.setEditable(true);MouseListener ml = new MouseAdapter() {//按下鼠标时候获得被拖动的节点public void mousePressed(MouseEvent e){//如果需要唯一确定某个节点，必须通过TreePath来获取。TreePath tp = tree.getPathForLocation(e.getX(), e.getY());if (tp != null){movePath = tp;}}//鼠标松开时获得需要拖到哪个父节点public void mouseReleased(MouseEvent e){//根据鼠标松开时的TreePath来获取TreePathTreePath tp = tree.getPathForLocation(e.getX(), e.getY());if (tp != null && movePath != null){//阻止向子节点拖动if (movePath.isDescendant(tp) && movePath != tp){JOptionPane.showMessageDialog(jf, "目标节点是被移动节点的子节点，无法移动！", "非法操作", JOptionPane.ERROR_MESSAGE );return;}//既不是向子节点移动，而且鼠标按下、松开的不是同一个节点else if (movePath != tp){System.out.println(tp.getLastPathComponent());//add方法可以先将原节点从原父节点删除，再添加到新父节点中((DefaultMutableTreeNode)tp.getLastPathComponent()).add((DefaultMutableTreeNode)movePath.getLastPathComponent());movePath = null;tree.updateUI();}}}};tree.addMouseListener(ml);JPanel panel = new JPanel();addSiblingButton.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent event){//获取选中节点DefaultMutableTreeNode selectedNode= (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();//如果节点为空，直接返回if (selectedNode == null) return;//获取该选中节点的父节点DefaultMutableTreeNode parent= (DefaultMutableTreeNode)selectedNode.getParent();//如果父节点为空，直接返回if (parent == null) return;//创建一个新节点DefaultMutableTreeNode newNode = new DefaultMutableTreeNode("新节点");//获取选中节点的选中索引int selectedIndex = parent.getIndex(selectedNode);//在选中位置插入新节点model.insertNodeInto(newNode, parent, selectedIndex + 1);//--------下面代码实现显示新节点（自动展开父节点）-------//获取从根节点到新节点的所有节点TreeNode[] nodes = model.getPathToRoot(newNode);//使用指定的节点数组来创建TreePathTreePath path = new TreePath(nodes);//显示指定TreePathtree.scrollPathToVisible(path);}});panel.add(addSiblingButton);addChildButton.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent event){//获取选中节点DefaultMutableTreeNode selectedNode= (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();//如果节点为空，直接返回if (selectedNode == null) return;//创建一个新节点DefaultMutableTreeNode newNode = new DefaultMutableTreeNode("新节点");//直接通过model来添加新节点，则无需通过调用JTree的updateUI方法//model.insertNodeInto(newNode, selectedNode, selectedNode.getChildCount());//直接通过节点添加新节点，则需要调用tree的updateUI方法selectedNode.add(newNode);//--------下面代码实现显示新节点（自动展开父节点）-------TreeNode[] nodes = model.getPathToRoot(newNode);TreePath path = new TreePath(nodes);tree.scrollPathToVisible(path);tree.updateUI();}});panel.add(addChildButton);deleteButton.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent event){DefaultMutableTreeNode selectedNode= (DefaultMutableTreeNode) tree.getLastSelectedPathComponent();if (selectedNode != null && selectedNode.getParent() != null){//删除指定节点model.removeNodeFromParent(selectedNode);}}});panel.add(deleteButton);editButton.addActionListener(new ActionListener(){public void actionPerformed(ActionEvent event){TreePath selectedPath = tree.getSelectionPath();if (selectedPath != null){//编辑选中节点tree.startEditingAtPath(selectedPath);}}});panel.add(editButton);jf.add(new JScrollPane(tree));jf.add(panel , BorderLayout.SOUTH);jf.pack();jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);jf.setVisible(true);} public static void main(String[] args) { new EditJTree().init(); }}

最后讲下如何修饰tree的图标，主要是通过拓展TreeCellRenderer来实现，eg

public class ExtendsDefaultTreeCellRenderer {JFrame jf = new JFrame("根据节点类型定义图标");JTree tree;//定义几个初始节点DefaultMutableTreeNode root = new DefaultMutableTreeNode(new NodeData(DBObjectType.ROOT , "数据库导航")); DefaultMutableTreeNode salaryDb = new DefaultMutableTreeNode(new NodeData(DBObjectType.DATABASE , "公司工资数据库"));DefaultMutableTreeNode customerDb = new DefaultMutableTreeNode(new NodeData(DBObjectType.DATABASE , "公司客户数据库"));//定义salaryDb的两个子节点DefaultMutableTreeNode employee = new DefaultMutableTreeNode(new NodeData(DBObjectType.TABLE , "员工表"));DefaultMutableTreeNode attend = new DefaultMutableTreeNode(new NodeData(DBObjectType.TABLE , "考勤表"));//定义customerDb的一个子节点DefaultMutableTreeNode contact = new DefaultMutableTreeNode(new NodeData(DBObjectType.TABLE , "联系方式表"));//定义employee的三个子节点DefaultMutableTreeNode id = new DefaultMutableTreeNode(new NodeData(DBObjectType.INDEX , "员工ID"));DefaultMutableTreeNode name = new DefaultMutableTreeNode(new NodeData(DBObjectType.COLUMN , "姓名"));DefaultMutableTreeNode gender = new DefaultMutableTreeNode(new NodeData(DBObjectType.COLUMN , "性别"));public void init()throws Exception{//通过add方法建立树节点之间的父子关系root.add(salaryDb);root.add(customerDb);salaryDb.add(employee);salaryDb.add(attend);customerDb.add(contact);employee.add(id);employee.add(name);employee.add(gender);//以根节点创建树tree = new JTree(root);//设置该JTree使用自定义的节点绘制器tree.setCellRenderer(new MyRenderer());//设置是否显示根节点的“展开/折叠”图标,默认是falsetree.setShowsRootHandles(true);//设置节点是否可见,默认是truetree.setRootVisible(true);//设置使用Windows风格外观UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel");//更新JTree的UI外观SwingUtilities.updateComponentTreeUI(tree);jf.add(new JScrollPane(tree));jf.pack();jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);jf.setVisible(true);} public static void main(String[] args) throws Exception {new ExtendsDefaultTreeCellRenderer().init(); }}//定义一个NodeData类，用于封装节点数据class NodeData{public int nodeType;public String nodeData;public NodeData(int nodeType , String nodeData){this.nodeType = nodeType;this.nodeData = nodeData;}public String toString(){return nodeData;}}//定义一个接口，该接口里包含数据库对象类型的常量interface DBObjectType{int ROOT = 0;int DATABASE = 1;int TABLE = 2;int COLUMN = 3;int INDEX = 4;}class MyRenderer extends DefaultTreeCellRenderer{//初始化5个图标ImageIcon rootIcon = new ImageIcon("icon/root.gif");ImageIcon databaseIcon = new ImageIcon("icon/database.gif");ImageIcon tableIcon = new ImageIcon("icon/table.gif");ImageIcon columnIcon = new ImageIcon("icon/column.gif");ImageIcon indexIcon = new ImageIcon("icon/index.gif");public Component getTreeCellRendererComponent(JTree tree, Object value,boolean sel, boolean expanded, boolean leaf, int row, boolean hasFocus){//执行父类默认的节点绘制操作super.getTreeCellRendererComponent(tree, value, sel, expanded, leaf, row, hasFocus);DefaultMutableTreeNode node = (DefaultMutableTreeNode)value;NodeData data = (NodeData)node.getUserObject();//根据数据节点里的nodeType数据决定节点图标ImageIcon icon = null;switch(data.nodeType){case DBObjectType.ROOT:icon = rootIcon;break;case DBObjectType.DATABASE:icon = databaseIcon;break;case DBObjectType.TABLE:icon = tableIcon;break;case DBObjectType.COLUMN:icon = columnIcon;break;case DBObjectType.INDEX:icon = indexIcon;break;}//改变图标this.setIcon(icon);return this;}}

图标大家就自己搞几个吧，不搞也可以看到效果。明天我将讲下JTable，也是个麻烦的控件。