Swing/TreeSelectionPaths の変更点

---
category: swing
folder: TreeSelectionPaths
title: JTreeで親ノードが展開されたときに子ノードの選択状態を変更する
tags: [JTree, DefaultMutableTreeNode, TreePath, TreeWillExpandListener]
author: aterai
pubdate: 2024-07-01T04:02:21+09:00
description: JTreeで親ノードが展開されたときにその選択状態で子ノードの選択状態も切り替えるTreeWillExpandListenerを作成します。
image: https://drive.google.com/uc?id=1gzLJzPPF-wTbpmMFjYwnqv5uXcx0iiGB
---
* Summary [#summary]
`JTree`で親ノードが展開されたときにその選択状態で子ノードの選択状態も切り替える`TreeWillExpandListener`を作成します。

#download(https://drive.google.com/uc?id=1gzLJzPPF-wTbpmMFjYwnqv5uXcx0iiGB)

* Source Code Examples [#sourcecode]
#code(link){{
JTree tree = new JTree();
tree.addTreeWillExpandListener(new TreeWillExpandListener() {
  @Override public void treeWillExpand(TreeExpansionEvent e) {
    JTree t = (JTree) e.getSource();
    TreePath anchor = t.getAnchorSelectionPath();
    TreePath lead = t.getLeadSelectionPath();
    TreePath path = e.getPath();
    Object o = path.getLastPathComponent();
    if (o instanceof DefaultMutableTreeNode && t.isPathSelected(path)) {
      DefaultMutableTreeNode n = (DefaultMutableTreeNode) o;
      TreePath[] paths = Collections.list((Enumeration<?>) n.children())
          .stream()
          .filter(DefaultMutableTreeNode.class::isInstance)
          .map(DefaultMutableTreeNode.class::cast)
          .map(DefaultMutableTreeNode::getPath)
          .map(TreePath::new)
          .toArray(TreePath[]::new);
      t.addSelectionPaths(paths);
      t.setAnchorSelectionPath(anchor);
      t.setLeadSelectionPath(lead);
    }
  }

  @Override public void treeWillCollapse(TreeExpansionEvent e) {
    /* do nothing */
  }
});
}}

* Description [#explanation]
* Description [#description]
- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/event/TreeExpansionEvent.html#getPath-- TreeExpansionEvent#getPath()]で展開予定の`TreePath`を取得
- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/tree/TreePath.html#getLastPathComponent-- TreePath#getLastPathComponent()]で`TreePath`の最後の要素(展開予定の`DefaultMutableTreeNode`)を取得
- 展開予定の`TreePath`が選択状態の場合、以下の手順で子の`TreeNode`配列を`TreePath`配列に変換して[https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/JTree.html#addSelectionPaths-javax.swing.tree.TreePath:A- JTree#addSelectionPaths(TreePath&#91;&#93;)]で選択状態に追加
-- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/tree/DefaultMutableTreeNode.html#children-- DefaultMutableTreeNode#children()]で子の`TreeNode`配列を取得
-- 取得した`TreeNode`配列が`DefaultMutableTreeNode`インスタンスの場合、[https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/tree/DefaultMutableTreeNode.html#getPath-- DefaultMutableTreeNode#getPath()]でルートノードから自身までの`TreeNode`配列を取得
-- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/tree/TreePath.html#TreePath-java.lang.Object:A- new TreePath(TreeNode&#91;&#93;)]で子の`TreePath`配列を生成
-- `JTree#addSelectionPaths(TreePath[])`で`JTree`(選択範囲の項目数に制限なし)の選択状態に追加
-- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/JTree.html#setAnchorSelectionPath-javax.swing.tree.TreePath- JTree#setAnchorSelectionPath(TreePath)]、[https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/JTree.html#setLeadSelectionPath-javax.swing.tree.TreePath- JTree#setLeadSelectionPath()]で選択のアンカー、リードパスを`JTree#addSelectionPaths(TreePath[])`実行前の状態に復元
- 展開予定の`TreePath`が未選択状態の場合はなにも実行しない

* Reference [#reference]
- [https://docs.oracle.com/javase/jp/8/docs/api/javax/swing/JTree.html#addSelectionPaths-javax.swing.tree.TreePath:A- JTree#addSelectionPaths(TreePath&#91;&#93;)]

* Comment [#comment]
#comment
#comment