使JTree叶子显示为空目录而不是文件 [英] Making a JTree leaf appear as an empty directory and not a file
问题描述
我正在学习Java JTree的方法，但我有一个我无法弄清楚的小问题。
使用我在Oracle网站上找到的教程，我模仿了他们演示的树形结构。问题是，我希望文件夹网站是一个空文件夹，但JTree显示它就好像它是一个文件。我如何告诉JTree网站实际上是一个空文件夹？
I'm learning my way around Java JTree's but I have this little problem I can't figure out. Using a tutorial I found on Oracle's site, I've mimicked a tree structure they demonstrate. The problem is, I want the Folder "websites" to be an empty folder, but JTree is displaying it as though it is a file. How can I tell the JTree that "websites" is in fact an empty folder?
更新
我开始研究一个简单的联系经理。我想要做的基本上它使名称看起来像文件夹（因为我想向每个人添加信息），但没有添加东西。即有些人可能没有任何信息，但我仍然希望他们看起来像文件夹。
I've started working on a simple 'contact manager'. What I want to do basically it make the name look like folders (since I want to add info to each of them), but without adding stuff. i.e. Some might not have any info in them, but I would still like them to look like folders.
浏览器类的代码：
import java.awt.Component;
import java.io.File;
import java.util.Iterator;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.tree.DefaultMutableTreeNode;
public class Browser extends JFrame implements javax.swing.tree.TreeModel {
private JTree tree;
ManagerOfContacts mngrOfContacts;
public Browser() {
//Generates the ManagerOfContacts and associated Contacts
Driver driver = new Driver();
mngrOfContacts = driver.getManagerOfContacts();
//---------------------------\\
DefaultMutableTreeNode contacts = new DefaultMutableTreeNode("Contacts");
createNodes(contacts);
tree = new JTree(contacts);
JScrollPane treeView = new JScrollPane(tree);
add(treeView);
setSize(400,400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public void createNodes(DefaultMutableTreeNode top){
DefaultMutableTreeNode contactName;
Iterator<Contact> contactItr = mngrOfContacts.getIterator();
while(contactItr.hasNext()){
contactName = new DefaultMutableTreeNode(contactItr.next());
top.add(contactName);
}
}
public static void main(String[] args) {
Browser browsr = new Browser();
}
}
推荐答案
这是你创建自己的 TreeCellRenderer 的方法，它告诉你的 JTree 你想要什么。由于您使用带有 DefaultMutableTreeNode 的默认树模型作为节点，因此您必须提取其用户对象并根据该对象决定要绘制的内容。请注意，默认渲染器只是一个扩展的 JLabel ，这就是为什么你可以使用 setIcon（...），里面有 setText（...）等。
This is how you create your own TreeCellRenderer which tells your JTree whatever you want. Since you are using a default tree model with DefaultMutableTreeNode as nodes you have to extract their user object and decide what to paint based on that. Note that the default renderer is just an extended JLabel, which is why you can use setIcon(...), setText(...), etc. inside it.
你的叶子节点被涂上文件的原因图标可能是默认渲染器选择基于 DefaultMutableTreeNode.getAllowsChildren（）的图标，类似于我如何使用 Contact.isSomeProperty（）。
The reason why your leaf nodes are painted with file icons is probably that the default renderer chooses the icon based on DefaultMutableTreeNode.getAllowsChildren() similarily to how I use Contact.isSomeProperty().
import java.awt.Component;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.UIManager;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeCellRenderer;
public class Browser extends JFrame {
private JTree tree;
//ManagerOfContacts mngrOfContacts;
public Browser() {
//Generates the ManagerOfContacts and associated Contacts
//Driver driver = new Driver();
//mngrOfContacts = driver.getManagerOfContacts();
//---------------------------\\
DefaultMutableTreeNode contacts = new DefaultMutableTreeNode("Contacts");
createNodes(contacts);
tree = new JTree(contacts);
// use your own renderer (!)
tree.setCellRenderer(new MyTreeCellRenderer());
JScrollPane treeView = new JScrollPane(tree);
add(treeView);
setSize(400,400);
setDefaultCloseOperation(EXIT_ON_CLOSE);
setVisible(true);
}
public final void createNodes(DefaultMutableTreeNode top){
DefaultMutableTreeNode contactName;
// dummies
List<Contact> contacts = new ArrayList<Contact>();
contacts.add(new Contact("Me", true));
contacts.add(new Contact("You"));
Iterator<Contact> contactItr = contacts.iterator();
while(contactItr.hasNext()){
contactName = new DefaultMutableTreeNode(contactItr.next());
top.add(contactName);
}
}
public static void main(String[] args) {
SwingUtilities.invokeLater(new Runnable() {
public void run() {
Browser browsr = new Browser();
}
});
}
// dummy
private static class Contact {
private boolean someProperty;
private String name;
public Contact(String name) {
this(name, false);
}
public Contact(String name, boolean property) {
this.someProperty = property;
this.name = name;
}
public boolean isSomeProperty() {
return someProperty;
}
public String getName() {
return name;
}
@Override
public String toString() {
return name;
}
}
// this is what you want
private static class MyTreeCellRenderer extends 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);
// decide what icons you want by examining the node
if (value instanceof DefaultMutableTreeNode) {
DefaultMutableTreeNode node = (DefaultMutableTreeNode) value;
if (node.getUserObject() instanceof String) {
// your root node, since you just put a String as a user obj
setIcon(UIManager.getIcon("FileView.computerIcon"));
} else if (node.getUserObject() instanceof Contact) {
// decide based on some property of your Contact obj
Contact contact = (Contact) node.getUserObject();
if (contact.isSomeProperty()) {
setIcon(UIManager.getIcon("FileView.hardDriveIcon"));
} else {
setIcon(UIManager.getIcon("FileChooser.homeFolderIcon"));
}
}
}
return this;
}
}
}
这应该让你开始吧您应该在 JTree教程中阅读更多相关信息。
This should get you started. You should read more about this in a JTree tutorial.
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