Java JTree延迟加载扩展
希望你做得很好 我有一个JTree,我使用数据库查询(每个节点)惰性地加载它。我在屏幕上有一个按钮,当用户单击该按钮时,我在数据库中执行一些Java JTree延迟加载扩展,java,swing,Java,Swing,希望你做得很好 我有一个JTree,我使用数据库查询(每个节点)惰性地加载它。我在屏幕上有一个按钮,当用户单击该按钮时,我在数据库中执行一些插入/更新/删除,然后使用SQL将模型添加回Jtree,仅使用根目录及其直接子目录(这会折叠树和选择,并且所有扩展节点都会折叠,因为它是一个延迟加载的树) 我想完成的是,在用户单击按钮插入/更新/删除之前,我读取所有展开的状态并将其保存在内存中,然后当我重新初始化JTree时,我通过这些展开的子节点循环调用JTree.expandPath,但它不展开节点:(
插入/更新/删除
,然后使用SQL将模型添加回Jtree
,仅使用根目录及其直接子目录(这会折叠树和选择,并且所有扩展节点都会折叠,因为它是一个延迟加载的树)
我想完成的是,在用户单击按钮插入/更新/删除之前,我读取所有展开的状态并将其保存在内存中,然后当我重新初始化JTree
时,我通过这些展开的子节点循环调用JTree.expandPath
,但它不展开节点:(
我甚至添加了一个TreeWillExpandListener
,在treeWillExpand
事件中,我添加了代码以从数据库中获取节点的子节点,我看到确实执行了查询以获取子目录,但JTree
仍然显示为已折叠
我真的需要你的帮助。请建议。这是代码片段
package marketdatagui;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeModel;
import javax.swing.tree.TreePath;
import javax.swing.event.TreeModelListener;
import javax.swing.event.TreeModelEvent;
import javax.swing.event.EventListenerList;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.util.List;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.io.File;
import java.io.Serializable;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
public class StressGroupModel
implements TreeModel,Serializable, Cloneable
{
protected EventListenerList listeners;
private static final Object LEAF = new Serializable() { };
private Map map;
private NodeData root;
private class NodeData{
String id;
String name;
public String toString(){
return name;
}
}
public StressGroupModel()
{
this.root = new NodeData();
root.id = "Root";
root.name = "Root";
this.listeners = new EventListenerList();
this.map = new HashMap();
List rootChildren = new ArrayList();
NodeData d1 = new NodeData();
d1.id = "5000007";
d1.name = "Name5000007";
rootChildren.add(d1);
NodeData d2 = new NodeData();
d2.id = "10000054";
d2.name = "Name10000054";
rootChildren.add(d2);
map.put(root.id, rootChildren);
}
public Object getRoot()
{
return root;
}
public boolean isLeaf(Object node)
{
return map.get(node) == LEAF;
}
public int getChildCount(Object node)
{
List children = children(node);
if (children == null)
return 0;
return children.size();
}
public Object getChild(Object parent, int index)
{
return children(parent).get(index);
}
public int getIndexOfChild(Object parent, Object child)
{
return children(parent).indexOf(child);
}
protected List children(Object node)
{
NodeData s = (NodeData)node;
Object value = map.get(s.id);
if (value == LEAF)
return null;
List children = (List)value;
if (!"Root".equals(s.id))
{
String[][] dbData = getChildren(s.id);
if (dbData != null)
{
children = new ArrayList(dbData.length);
for (int i = 0; i < dbData.length; i++)
{
NodeData d = new NodeData();
d.id = dbData[i][1];
d.name = dbData[i][1] + "Name";
children.add(d);
if ("R".equals(dbData[i][2]))
map.put(d, LEAF);
}
}
else
children = new ArrayList(0);
map.put(s.id, children);
}
return children;
}
private String[][] getChildren(String parent_uid){
String sql = "select parent_uid,child_uid,child_type from stress_groups_mapping "
+ " where parent_uid="+ parent_uid
+" order by parent_uid, child_uid";
return Util.getTableData(sql);
}
public void valueForPathChanged(TreePath path, Object value)
{
}
public void addTreeModelListener(TreeModelListener l)
{
listeners.add(TreeModelListener.class, l);
}
public void removeTreeModelListener(TreeModelListener l)
{
listeners.remove(TreeModelListener.class, l);
}
public Object clone()
{
try
{
StressGroupModel clone = (StressGroupModel)super.clone();
clone.listeners = new EventListenerList();
clone.map = new HashMap(map);
return clone;
}
catch (CloneNotSupportedException e)
{
throw new InternalError();
}
}
}
- 下面是我如何保存扩展状态的
- 是否插入/更新/删除数据库内容
- 现在重新初始化模型并添加回JTree(因此它选择最新的 来自数据库的值)
- 现在我循环并调用expand来扩展用户扩展的节点 在他点击按钮但不幸的是,按钮一直处于折叠状态之前:(
感谢尽快提供更好的帮助,发布一篇文章。我在一个自定义节点类中遇到了类似的问题-结果证明我的
equals
方法不太正确。哇。我花了几个小时,不明白expandPath()为什么不起作用。访问这么多论坛并阅读相同的建议真是令人沮丧:(使用“expandPath(),setSelectionPath()“等等)。但它根本不起作用。谢谢!!!
JFrame f = new JFrame("Tree Dragging Tester");
DefaultMutableTreeNode root = new DefaultMutableTreeNode(new Object());
jtree = new JTree(new StressGroupModel());
TreeWillExpandListener treeWillExpandListener = new TreeWillExpandListener() {
public void treeWillCollapse(TreeExpansionEvent treeExpansionEvent)
throws ExpandVetoException {
}
public void treeWillExpand(TreeExpansionEvent treeExpansionEvent) throws ExpandVetoException {
TreePath path = treeExpansionEvent.getPath();
Object node = path.getLastPathComponent();
((StressGroupModel)jtree.getModel()).getChildCount(node);
}
};
jtree.addTreeWillExpandListener(treeWillExpandListener);
f.getContentPane().add(jtree, BorderLayout.CENTER);
f.setSize(300, 200);
f.setVisible(true);
}
TreePath treePath = (TreePath) paths.nextElement();
try {
jtree.expandPath(treePath);
jtree.setSelectionPath(treePath);
}
catch(Exception ex){
}
}