【发布时间】：2016-04-24 04:52:32
【问题描述】：
有几个相关的问题，关于auto-expanding a JTree when a new TreeModel is set，或者关于expanding a JTree in general，其中一些也是针对expanding many paths in a JTree的性能。
但是，所提出的解决方案似乎都没有涵盖人们认为的“简单”应用案例：我有一棵大树（即，一棵非常深、非常宽或两者兼有的树），而我希望以编程方式完全扩展它。
以下是显示问题的MCVE：它创建了一个具有 100k 节点的树模型。按下该按钮会触发对expandAll 的调用，它会尝试使用从相关问题的答案中得出的方法来扩展所有节点。
问题在于扩展这 10 万个节点大约需要 13 秒（在普通机器上，使用最新的 JVM）。
import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.util.function.Consumer;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTree;
import javax.swing.SwingUtilities;
import javax.swing.tree.DefaultMutableTreeNode;
import javax.swing.tree.DefaultTreeModel;
import javax.swing.tree.TreeModel;
public class TreeExpansionPerformanceProblem
{
public static void main(String[] args)
{
SwingUtilities.invokeLater(
() -> createAndShowGUI());
}
private static void createAndShowGUI()
{
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.getContentPane().setLayout(new GridLayout(1,0));
f.getContentPane().add(createTestPanel(
TreeExpansionPerformanceProblem::expandAll));
f.setSize(800,600);
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private static JPanel createTestPanel(Consumer<JTree> expansionMethod)
{
JPanel panel = new JPanel(new BorderLayout());
JTree tree = new JTree(createTestTreeModel());
panel.add(new JScrollPane(tree), BorderLayout.CENTER);
JPanel buttonPanel = new JPanel();
JButton expandAllButton = new JButton("Expand all");
expandAllButton.addActionListener( e ->
{
System.out.println("Expanding...");
long before = System.nanoTime();
expansionMethod.accept(tree);
long after = System.nanoTime();
System.out.println("Expanding took "+(after-before)/1e6);
});
buttonPanel.add(expandAllButton);
panel.add(buttonPanel, BorderLayout.SOUTH);
return panel;
}
private static void expandAll(JTree tree)
{
int r = 0;
while (r < tree.getRowCount())
{
tree.expandRow(r);
r++;
}
}
private static TreeModel createTestTreeModel()
{
DefaultMutableTreeNode root = new DefaultMutableTreeNode("JTree");
addNodes(root, 0, 6, 6, 10);
return new DefaultTreeModel(root);
}
private static void addNodes(DefaultMutableTreeNode node,
int depth, int maxDepth, int count, int leafCount)
{
if (depth == maxDepth)
{
return;
}
for (int i=0; i<leafCount; i++)
{
DefaultMutableTreeNode leaf =
new DefaultMutableTreeNode("depth_"+depth+"_leaf_"+i);
node.add(leaf);
}
if (depth < maxDepth - 1)
{
for (int i=0; i<count; i++)
{
DefaultMutableTreeNode child =
new DefaultMutableTreeNode("depth_"+depth+"_node_"+i);
node.add(child);
addNodes(child, depth+1, maxDepth, count, leafCount);
}
}
}
}
是否有任何选项可以更有效地扩展多个节点？
【问题讨论】：
标签： java performance swing jtree