JScrollPanel中沒有出現多個JTree

Question

我使用此處提到的第一個示例創建我的JTree，但我想在JscrollPanel中將多個樹作為根。 我只是更改了框的布局，並使用相同的代碼創建了另外一棵樹，但是當我運行該程序時，樹對我卻不顯示。

這是我的代碼

import java.awt.*;
import javax.swing.*;
import javax.swing.tree.*;

public class SimpleTree extends JFrame {
  public static void main(String[] args) {
    new SimpleTree();
  }

  public SimpleTree() {
    super("Creating a Simple JTree");
    Container content = getContentPane();
    Object[] hierarchy =
      { "javax.swing",
        "javax.swing.border",
        "javax.swing.colorchooser",
        "javax.swing.event",
        "javax.swing.filechooser",
        new Object[] { "javax.swing.plaf",
                       "javax.swing.plaf.basic",
                       "javax.swing.plaf.metal",
                       "javax.swing.plaf.multi" },
        "javax.swing.table",
        new Object[] { "javax.swing.text",
                       new Object[] { "javax.swing.text.html",
                                      "javax.swing.text.html.parser" },
                       "javax.swing.text.rtf" },
        "javax.swing.tree",
        "javax.swing.undo" };
    DefaultMutableTreeNode root = processHierarchy(hierarchy);
    DefaultMutableTreeNode root2 = processHierarchy(hierarchy);
    JTree tree = new JTree(root);
    JTree tree2 = new JTree(root2);
    content.setLayout(new BoxLayout(this,BoxLayout.Y_AXIS));
    content.add(new JScrollPane(tree));
    content.add(new JScrollPane(tree2));
    setSize(getPreferredSize());
    setVisible(true);
  }

  /** Small routine that will make node out of the first entry
   *  in the array, then make nodes out of subsequent entries
   *  and make them child nodes of the first one. The process is
   *  repeated recursively for entries that are arrays.
   */

  private DefaultMutableTreeNode processHierarchy(Object[] hierarchy) {
    DefaultMutableTreeNode node =
      new DefaultMutableTreeNode(hierarchy[0]);
    DefaultMutableTreeNode child;
    for(int i=1; i<hierarchy.length; i++) {
      Object nodeSpecifier = hierarchy[i];
      if (nodeSpecifier instanceof Object[])  // Ie node with children
        child = processHierarchy((Object[])nodeSpecifier);
      else
        child = new DefaultMutableTreeNode(nodeSpecifier); // Ie Leaf
      node.add(child);
    }
    return(node);
  }
}

有人可以幫我這個忙。 所有幫助將不勝感激。

謝謝Ashish Tyagi

Answer 1

JScrollPane在其ViewPort具有單個子組件的視圖。

但是，您可以將2個JScrollPane組件放置在單個面板上，例如均勻分割的GridLayout(2, 1)並將JScrollPane的視圖設置為新面板。

另外 ：您應該使用ContentPane作為BoxLayout的容器：

content.setLayout(new BoxLayout(content, BoxLayout.Y_AXIS));

Answer 2

• 必須接受未指定JScrollPane容納多個JComponents

• 你可以把JPanel到JScrollPane ，把所需的數量JTree s到（在JScrollPane ） JPanel ，也許使用GridLayout進行JPanel

• 注意在父JScrollPane和每個JScrollPane與JTree之間可滾動的可能的並發性