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首页 > 解决方案 > 为什么 sun.swing.FilePane 可以强制转换为 javax.swing.table？

java - 为什么 sun.swing.FilePane 可以强制转换为 javax.swing.table？

问题描述

所以，我正在寻找一种按日期对 jFileChooser 进行排序的方法，我发现了这个讨论：Start a JFileChooser with files ordered by date

该解决方案有效。虽然，这段代码让我感到困惑： JTable table = SwingUtils.getDescendantsOfType(JTable.class, fileChooser).get(0);

我决定使用 println() 检查表实例的类型，结果如下：sun.swing.FilePane$6...

这个 FilePane 引起了我的兴趣。所以，我决定寻找 FilePane 的源代码，我发现了这个： http: //www.docjar.com/html/api/sun/swing/FilePane.java.html

在源代码中，FilePane 没有扩展 JTable。不过，FilePane 将 JTable 作为组件。FilePane 怎么可能被转换成 JTable？

我查看了 SwingUtils 源代码，发现了一些 getDescendantsOfType() 方法的实现。

   public static <T extends JComponent> List<T> getDescendantsOfType(
         Class<T> clazz, Container container) {
      return getDescendantsOfType(clazz, container, true);
   }

   public static <T extends JComponent> List<T> getDescendantsOfType(
         Class<T> clazz, Container container, boolean nested) {
      List<T> tList = new ArrayList<T>();
      for (Component component : container.getComponents()) {
         if (clazz.isAssignableFrom(component.getClass())) {
            tList.add(clazz.cast(component));
         }
         if (nested || !clazz.isAssignableFrom(component.getClass())) {
            tList.addAll(SwingUtils.<T>getDescendantsOfType(clazz,
                  (Container) component, nested));
         }
      }
      return tList;
   }

我尝试使用 cast 运算符将 FilePane 转换为 JTable，但没有成功。我对Class<T>类知之甚少，所以我对这个类的方法不是很熟悉。

标签： javaswingcasting

解决方案

In the source code, FilePane doesn't extend JTable.

Correct.

How is it possible for FilePane to be casted to JTable?

It can't.

sun.swing.FilePane$6...

The $6 implies that it is an inner class defined in the FilePane class.

Inner class names start at $1 and increase for each inner class.

From the class you can see:

 final JTable detailsTable = new JTable(getDetailsTableModel()) {
       // Handle Escape key events here
       protected boolean processKeyBinding(KeyStroke ks, KeyEvent e, int condition, boolean pressed) {
           if (e.getKeyCode() == KeyEvent.VK_ESCAPE && getCellEditor() == null) {
               // We are not editing, forward to filechooser.
               chooser.dispatchEvent(e);
               return true;
           }
           return super.processKeyBinding(ks, e, condition, pressed);
       }
   
       public void tableChanged(TableModelEvent e) {
           super.tableChanged(e);
   
           if (e.getFirstRow() == TableModelEvent.HEADER_ROW) {
               // update header with possibly changed column set
               updateDetailsColumnModel(this);
           }
       }
   };

You can see the JTable inner class overrides the:

  1. processKeyBinding(), and
  2. tableChanged()

methods.

You should be able to see inner class files when you compile your source code and use inner classes.

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