从defaultmutabletreenode生成的遍历树

如果你想穿过这棵树,你可以调用 breadthFirstEnumeration() 或 depthFirstEnumeration() 以便遍历树中的所有节点。

例子:

DefaultMutableTreeNode root = ...

Enumeration en = root.depthFirstEnumeration();
while (en.hasMoreElements()) {

  // Unfortunately the enumeration isn't genericised so we need to downcast
  // when calling nextElement():
  DefaultMutableTreeNode node = (DefaultMutableTreeNode) en.nextElement();
}

理论上,你有四种方法可以从一个节点走到树上( DefaultMutableTreeNode ):

• breadthFirstEnumeration
• depthFirstEnumeration
• preorderEnumeration
• postorderEnumeration

但实际上,深度优先是作为后序实现的。
JavaDoc对这些方法的差异有点简明扼要。我来这里寻找答案,但最后我自己做了测试,代码如下:

  TreeModel model = tree.getModel();

  DefaultMutableTreeNode rootNode = (DefaultMutableTreeNode) model.getRoot();
  // Just changing enumeration kind here
  Enumeration<DefaultMutableTreeNode> en = rootNode.preorderEnumeration();
  while (en.hasMoreElements())
  {
     DefaultMutableTreeNode node = en.nextElement();
     TreeNode[] path = node.getPath();
     System.out.println((node.isLeaf() ? "  - " : "+ ") + path[path.length - 1]);
  }

我本可以根据等级来调整缩进,但这只是一个快速的修改。

那么,有什么区别呢?

• 预购 =从树的顶部到底部,就像你用向下箭头来移动它一样。
• PostOrderEnumeration = 深度优先枚举 =首先列出第一条路径的最深叶,然后列出它们的父级,然后列出第二条路径的最深叶,等等。
• breadthfirstEnumeration =列出第一级的元素,然后列出第二级的元素,依此类推。

要更具体:

+ Root
  + Folder 1
    - Leaf F1
    - Leaf F1
 + Folder 2
    + Sub-folder 1
      - Leaf SF1
      - Leaf SF1
    + Sub-folder 2
      - Leaf SF2
      - Leaf SF2

_墠预购:如上所示
_墠depthfirst/postorder:
叶F1,叶F1,文件夹1
叶SF1,叶SF1,子文件夹1
叶SF 2,叶SF2,子文件夹2,文件夹2,根目录
呼吸优先:
根
文件夹1,文件夹2
叶F1,叶F1,子文件夹1,子文件夹2
叶SF 1,叶SF 1,叶SF 2,叶SF 2

下面是对3种枚举方法的另一种描述,这可能更容易理解。

en = root.breadthFirstEnumeration();
//Enumeration lists all nodes at depth 0 (aka root)
//Then all nodes at depth 1 (aka root's children, top to bottom ordering)
//Then all nodes at depth 2, and so on till max depth reached

en = root.preorderEnumeration(); 
//Imagine your JTree is fully expanded (where each node = a row)
//Enumeration will list nodes from top to bottom (regardless of leaf or not)

en = root.postorderEnumeration(); //Equivalent to root.depthFirstEnumeration();
//Imagine a fully expanded copy of your JTree (where each node = a row)
//This will allow you to visualize what Enumeration List will look like
while(treecopy.hasNodes() ) {
list 1st leaf sighted going from top to bottom, then remove that leaf }
//as the leafs are removed, branches then become leafs, and root is last enumerated.

对,breadtfirst不太好。也支持预排序(先是根目录,然后是子目录)(预排序)