'SwingUtilities.updateComponentTreeUI(this)'从JComboBox中删除自定义文档 [英] 'SwingUtilities.updateComponentTreeUI(this)' removes custom Document from JComboBox

问题描述

我有一个可编辑的JComboBox和JTextField.两者都带有自定义文档.这是代码:

I have an editable JComboBox and JTextField. Both with custom Documents. Here is the code:

import java.awt.*;
import javax.swing.*;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

public class SwingUtilStrangeBehav extends JFrame {

    public SwingUtilStrangeBehav() {
       JComboBox<String> combo = new JComboBox<>(new String[]{"a", "b", "c"});
       combo.setEditable(true); 

       ((JTextField)combo.getEditor().getEditorComponent()).setDocument(new PlainDocument() {
            private static final long serialVersionUID = 1L;

            @Override
            public void insertString(int offs, String str, AttributeSet a)
                        throws BadLocationException {

                    System.out.println("New text inserted into combo!");
                    super.insertString(offs, str, a);
            }
      });

      JTextField field = new JTextField();
      field.setDocument(new PlainDocument() {
          private static final long serialVersionUID = 1L;

          @Override
          public void insertString(int offs, String str, AttributeSet a)
                        throws BadLocationException {

                  System.out.println("New text inserted into text!");
                  super.insertString(offs, str, a);
          }
    });

    Container c = getContentPane();
    c.setLayout(new BoxLayout(c, BoxLayout.PAGE_AXIS));

    c.add(combo);
    c.add(Box.createRigidArea(new Dimension(0, 5)));
    c.add(field);

    //SwingUtilities.updateComponentTreeUI(this);

    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    pack();
    setLocationRelativeTo(null);
    setVisible(true);
  }

  public static void main(String arg[]) {
     java.awt.EventQueue.invokeLater(new Runnable() {

         @Override
         public void run() {
             new SwingUtilStrangeBehav();
         }
     });
  }
}

然后我在JComboBox或JTextField中输入一些文本，例如，在控制台中获得以下输出:

Then I input some text in JComboBox or JTextField I get the following output in my console, for example:

新文本已插入组合！
在文本中插入了新文本！

太好了！当取消注释以下行 SwingUtilities.updateComponentTreeUI(this); 并运行该程序时，我只能得到以下输出:

在文本中插入了新文本！

That's great! When I uncomment the following line SwingUtilities.updateComponentTreeUI(this); and run this programm, I can only get this output:

New text inserted into text!

似乎JComboBox的文档已删除.为什么要删除自定义文档以及如何解决此问题?我希望自定义文档在执行 SwingUtilities.updateComponentTreeUI(this); 后仍将位于JComboBox中.

It seems that JComboBox's Document was removed. Why was custom Document removed and how to solve this problem? I want that custom Document would still be in JComboBox after executing SwingUtilities.updateComponentTreeUI(this);.

仅供参考:我使用 SwingUtilities.updateComponentTreeUI(this); 将新字体应用于容器.

FYI: I use SwingUtilities.updateComponentTreeUI(this); to apply new Font to Container.

推荐答案

之所以发生这种情况，是因为JComboBox的编辑器是由其UI-Delegate(即XXComboBoxUI)控制的:随着updateUI设置新的ui，受控的编辑器也将被替换.几个选项:

This happens because the JComboBox's editor is controlled by its UI-Delegate, that is XXComboBoxUI: as updateUI sets a new ui, the controlled editor is replaced as well. A couple of options:

• 在comboBox上注册一个propertyChangeListener，以便在替换编辑器时得到通知，并再次设置自定义文档
• 安装自定义编辑器(而不是仅安装自定义文档)
• (可能不是一个选择，以防万一)不要使用updateUI，而是在容器中设置字体

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