Dynamically populating the tree model from a text file in JTree

问题

The problem I am facing is with the tree model of the JTree.

I have defined the root node as:

    javax.swing.tree.DefaultMutableTreeNode rootNode = new javax.swing.tree.DefaultMutableTreeNode(projectName);

When the application first starts, I want the treeModel to be created and loaded. For this, I am using a file meta.txt, which has information like the following:

    1QuotesPrice.Job
    2QuotesPrice.Df
    1Quotes.Job
    2Quotes.Wf
    3Quotes.Df
    2Falkeblang.Wf
    3Falkeblang.Df

The first column is the level, and the second is the node of the tree. Now based on this information, I want to create the tree model, but am facing a roadblock here.

I am unsure of the logic to apply to add the above nodes to the root node. Every thing I have tried seems to have flaws. The problem here is the no of levels are not fixed, so I cant simply use a if-else construct. I am using the following code:

        String treeMeta=this.projectsDir+"\\"+projectName+"\\"+"meta.txt";
        DefaultMutableTreeNode rootNode = new DefaultMutableTreeNode(projectName);
        File f1=new File(treeMeta);
        inputStream =  new Scanner(f1);
        while(inputStream.hasNext()){

         String val=inputStream.next();
         System.out.println("!@#$%"+val+"!@#$%");
         treeNodePrev=treeNode;
         prevLevel=level;
         level=val.substring(0,1);
         nodeVal=val.substring(1);
           if(level.equals("1")){
              prevNode=projectName;
              treeNode = new DefaultMutableTreeNode(nodeVal);
              System.out.println("added to root node");
              rootNode.add(treeNode);
              //System.out.println("added to root node");
           }else if(Integer.parseInt(level)>Integer.parseInt(prevLevel)){
               prevNode=nodeVal;
               treeNode = new DefaultMutableTreeNode(nodeVal);
               treeNodePrev.add(treeNode);
           }else if(Integer.parseInt(level)==Integer.parseInt(prevLevel)){
               prevNode=nodeVal;
               treeNode = new DefaultMutableTreeNode(nodeVal);
               prevParentTreeNode=(DefaultMutableTreeNode)treeNodePrev.getParent();
               //System.out.println(prevParentTreeNode.getParent().toString());
               prevParentTreeNode.add(treeNode);
           }
        }
         jProjectTree.setModel(new javax.swing.tree.DefaultTreeModel(rootNode));
         jScrollPane2.setViewportView(jProjectTree);

This seems to be working fine, but could anyone please tell me if this is the correct approach?

回答1:

This might be a bit cleaner. Just adapt the function for calculating the level ...

public static final DefaultMutableTreeNode getTreeNode(File file) throws IOException  {

    DefaultMutableTreeNode rootNode = null;
    Map<Integer, DefaultMutableTreeNode> levelNodes = new HashMap<Integer, DefaultMutableTreeNode>();
    BufferedReader reader = new BufferedReader(new FileReader(file));
    String line;

    while( (line = reader.readLine()) != null ) {

        int level = getLevel(line);
        String nodeName = getNodeName(line, level);
        DefaultMutableTreeNode node = new DefaultMutableTreeNode(nodeName);               
        levelNodes.put(level, node);
        DefaultMutableTreeNode parent = levelNodes.get(level - 1);

        if( parent != null ) {
            parent.add(node);
        }
        else {
            rootNode = node;
        }
    }    
    reader.close();
    return rootNode;
}

private static final int getLevel(String line) {

    int level = 0;
    for ( int i = 0; i < line.length(); i++ ) {
        char c = line.charAt(i);
        if( c == '\t') {
            level++;
        }
        else {
            break;
        }
    }
    return level;
}

private static final String getNodeName(String line, int level) {
    return line.substring(level);
}      

回答2:

There is a github project for creating TreeModels from a Collection of data if that helps.

Example below on building a TreeModel from a List of Book Objects.

List<Book> bookList = new ArrayList<>();

CollectionTreeModel<Book> treeModel = new CollectionTreeModel
        .Builder<>(bookList)
        .addNode(b -> b.publisher)
        .addNode(b -> b.author)
        .addNode(b -> b.title)
        .build();

JTree jTree = new JTree(treeModel);

Assumes Book is in same package and looks like...

public class Book {
    final String publisher;
    final String author;
    final String title;

    Book(String publisher, String author, String title) {
        ...
    }
}

For more info:

https://github.com/mnrussell/collectionTreeModel

Bit late but hope this helps :o)

来源：https://stackoverflow.com/questions/18483191/dynamically-populating-the-tree-model-from-a-text-file-in-jtree