java - 如何知道 Swing JTree 何时呈现所有更改？

Question

所以我修改了我的树结构并要求我的树模型重新加载它。如何知道 JTree 组件何时完成渲染更改？

Answer 1

以下 Oracle 文档对此进行了部分介绍:

• How to use trees
• How to Write a Tree Model Listener
• TreeModelListener 并实现类

<小时/>

通过添加您自己的监听器，您可以监视更改。然而，DefaultTreeModel通知更改时从最后到第一个处理监听器(来源:DefaultTreeModel):

// Process the listeners last to first, notifying those that are interested in this event

因此，为了确保您的监听器在更改呈现/完成后收到通知，您需要在JTree内部已使用的监听器之后执行您的监听器。来处理变化。通过扩展DefaultTreeModel并覆盖这些方法，您可以通过修改 for 循环/引入排序来更改监听器的处理顺序

DynamicTreeDemo和DynamicTree上面链接的教程为您自己进行测试提供了良好的基础，因为它们提供了编辑、插入和删除树节点的方法，以及通过 UI 完全修改树结构(清除选项)的方法。其中每一个都对应TreeModelListener中的一个方法必须实现

<小时/>

以下是您可以通过包含来测试的示例

treeModel = new CustomTreeModel(rootNode);
treeModel.addTreeModelListener(new CustomTreeModelListener());

在 DynamicTree构造函数

您还可以添加额外的TreeModelListener确保它们按预期顺序执行

型号:

class CustomTreeModel extends DefaultTreeModel{
        public CustomTreeModel(TreeNode root){
            super(root);
        }

        @Override
        protected void fireTreeNodesChanged(Object source, Object[] path,
                                            int[] childIndices, Object[] children) {

            Object[] listeners = listenerList.getListenerList();
            TreeModelEvent event = null;
            // Process the listeners first to last, notifying those that are interested in this event
            for (int index = 0; index < listeners.length; index++) {
                if (listeners[index] instanceof TreeModelListener) {
                    // Lazily create the event:
                    if (event == null)
                        event = new TreeModelEvent(source, path, childIndices, children);
                    ((TreeModelListener)listeners[index]).treeNodesChanged(event);
                }
            }
        }

        @Override
        protected void fireTreeNodesInserted(Object source, Object[] path,
                                             int[] childIndices, Object[] children) {

            Object[] listeners = listenerList.getListenerList();
            TreeModelEvent event = null;
            // Process the listeners first to last, notifying those that are interested in this event
            for (int index = 0; index < listeners.length; index++) {
                if (listeners[index] instanceof TreeModelListener) {
                    // Lazily create the event:
                    if (event == null)
                        event = new TreeModelEvent(source, path, childIndices, children);
                    ((TreeModelListener)listeners[index]).treeNodesInserted(event);
                }
            }
        }

        @Override
        protected void fireTreeNodesRemoved(Object source, Object[] path,
                                            int[] childIndices, Object[] children) {

            Object[] listeners = listenerList.getListenerList();
            TreeModelEvent event = null;
            // Process the listeners first to last, notifying those that are interested in this event
            for (int index = 0; index < listeners.length; index++) {
                if (listeners[index] instanceof TreeModelListener) {
                    // Lazily create the event:
                    if (event == null)
                        event = new TreeModelEvent(source, path, childIndices, children);
                    ((TreeModelListener)listeners[index]).treeNodesRemoved(event);
                }
            }
        }

        @Override
        protected void fireTreeStructureChanged(Object source, Object[] path,
                                                int[] childIndices, Object[] children) {

            Object[] listeners = listenerList.getListenerList();
            TreeModelEvent event = null;
            // Process the listeners first to last, notifying those that are interested in this event
            for (int index = 0; index < listeners.length; index++) {
                if (listeners[index] instanceof TreeModelListener) {
                    // Lazily create the event:
                    if (event == null)
                        event = new TreeModelEvent(source, path, childIndices, children);
                    ((TreeModelListener)listeners[index]).treeStructureChanged(event);
                }
            }
        }
    }

听众:

class CustomTreeModelListener implements TreeModelListener {
    public void treeNodesChanged(TreeModelEvent e) {
        DefaultMutableTreeNode parentNode = (DefaultMutableTreeNode)e.getTreePath().getLastPathComponent();
        int index = e.getChildIndices()[0];
        DefaultMutableTreeNode modifiedNode = (DefaultMutableTreeNode)(parentNode.getChildAt(index));

        System.out.println("A node on parent: " + parentNode.getUserObject()
                + " was modified to: " + modifiedNode.getUserObject());
    }

    public void treeNodesInserted(TreeModelEvent e) {
        String parentNode = e.getTreePath().getLastPathComponent().toString();
        String childNodes = Arrays.toString(e.getChildren());
        System.out.println("Node(s): " + childNodes + " inserted to parent: " + parentNode);
    }

    public void treeNodesRemoved(TreeModelEvent e) {
        String parentNode = e.getTreePath().getLastPathComponent().toString();
        String childNodes = Arrays.toString(e.getChildren());
        System.out.println("Node(s): " + childNodes + " removed from parent: " + parentNode);
    }

    public void treeStructureChanged(TreeModelEvent e) {
        System.out.println("Tree structure has been updated");
    }
}