java swing tree树的懒加载

/* * To change this template, choose Tools | Templates * and open the template in the editor. */ package cn.vearn.asynchtree; import java.awt.BorderLayout; import java.awt.EventQueue; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import javax.swing.JCheckBox; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTree; import javax.swing.SwingWorker; import javax.swing.UIManager; import javax.swing.event.TreeExpansionEvent; import javax.swing.event.TreeExpansionListener; import javax.swing.tree.DefaultTreeModel; public class TestFrame extends JFrame { private static final long serialVersionUID = 1L; public TestFrame() { super("asynch_load_tree"); JPanel northPanel = new JPanel(); final JCheckBox cb = new JCheckBox("点我看长时间阻塞EDT的后果"); northPanel.add(cb); JPanel southPanel = new JPanel(); final JLabel label = new JLabel("异步加载树DEMO"); southPanel.add(label); final DefaultTreeModel treeModel = initTreeModel(); final JTree tree = new JTree(treeModel); // JTree构造方法 tree.setShowsRootHandles(true); // 显示根结点左边的控制手柄 tree.collapseRow(0); // 初始时只显示根结点 // 注册TreeExpansionListener、监听结点展开事件 tree.addTreeExpansionListener(new TreeExpansionListener() { @Override public void treeExpanded(TreeExpansionEvent event) { // 首先获取展开的结点 final MyTreeNode expandNode = (MyTreeNode) event.getPath().getLastPathComponent(); // 判断该节点是否已经被访问过 // 是——无需到数据库中读取、什么事也不做 // 否——开始异步加载 if (!expandNode.isVisited()) { expandNode.setVisited(true); // 先改变visited字段的状态 tree.setEnabled(false); // 暂时禁用JTree // 更新JLabel信息 label.setText("正在加载结点[" + expandNode.getNodeName() + "]..."); if (cb.isSelected()) { long handleTime = asynchLoad(expandNode, treeModel); treeModel.removeNodeFromParent(expandNode.getFirstLeaf()); // 加载完毕后要删除“载入中...”结点 tree.setEnabled(true); // 使JTree可用 label.setText("加载结点[" + expandNode.getNodeName() + "]完毕、耗时" + handleTime + "ms"); } else { // 使用swingworker框架 new SwingWorker<Long, Void>() { @Override protected Long doInBackground() throws Exception { return asynchLoad(expandNode, treeModel); } @Override protected void done() { treeModel.removeNodeFromParent(expandNode.getFirstLeaf()); treeModel.nodeStructureChanged(expandNode); // 通知视图结构改变 tree.setEnabled(true); try { // 获取doInBackground方法的返回值 label.setText("加载结点[" + expandNode.getNodeName() + "]完毕、耗时" + get() + "ms"); } catch (Exception ex) { } } }.execute(); } } } @Override public void treeCollapsed(TreeExpansionEvent event) { } }); getContentPane().add(northPanel, BorderLayout.NORTH); getContentPane().add(southPanel, BorderLayout.SOUTH); getContentPane().add(new JScrollPane(tree), BorderLayout.CENTER); setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setSize(600, 450); } public static void main(String args[]) throws Exception { UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName()); // 设定界面观感 EventQueue.invokeLater(new Runnable() { @Override public void run() { new TestFrame().setVisible(true); } }); } // 从数据库中读取根结点、并增加“载入中...”子结点 private DefaultTreeModel initTreeModel() { DefaultTreeModel treeModel = null; Connection conn = DBConn.getConn(); PreparedStatement ps = null; ResultSet rs = null; try { ps = conn.prepareStatement("SELECT * FROM nodes WHERE parent_id=0"); rs = ps.executeQuery(); if (rs.next()) { MyTreeNode root = new MyTreeNode(rs.getInt("node_id"), rs.getString("node_name")); treeModel = new DefaultTreeModel(root); if ("1".equals(rs.getString("is_leaf"))) { addLoadingNode(treeModel, root); } } } catch (Exception ex) { } finally { DBConn.closeAll(conn, ps, rs); } return treeModel; } // 增加“载入中...”子结点的方法 private void addLoadingNode(DefaultTreeModel treeModel, MyTreeNode parent) { MyTreeNode loading = new MyTreeNode("载入中..."); treeModel.insertNodeInto(loading, parent, parent.getChildCount()); } // 从数据表中读取expandNode的子结点.返回值为处理时长 private long asynchLoad(MyTreeNode expandNode, DefaultTreeModel treeModel) { long handleTime = 0L; // 本次异步加载的处理时长 long start = System.currentTimeMillis(); // 开始处理的时刻 // 从数据库中读取父结点是expandNode的所有记录 Connection conn = DBConn.getConn(); PreparedStatement ps = null; ResultSet rs = null; try { // Thread.sleep(3000); // sleep一段时间以便看清楚整个过程 ps = conn.prepareStatement("SELECT * FROM nodes WHERE parent_id=?"); ps.setInt(1, expandNode.getNodeId()); rs = ps.executeQuery(); while (rs.next()) { MyTreeNode obj = new MyTreeNode(rs.getInt("node_id"), rs.getString("node_name")); // 如果此结点不是叶子节点 // 给它加上一个“载入中...”的子结点 // 使这个结点左边绘制控制手柄.点击它(或者双击这个结点)可以触发TreeExpansionEvent if ("1".equals(rs.getString("is_leaf"))) { addLoadingNode(treeModel, obj); } // 把这个节点加入到expandNode中 treeModel.insertNodeInto(obj, expandNode, expandNode.getChildCount()); } } catch (Exception ex) { ex.printStackTrace(); } finally { DBConn.closeAll(conn, ps, rs); // 关闭数据库连接 handleTime = System.currentTimeMillis() - start; // 计算出处理时长 } return handleTime; } }