Using DocumentFilter.FilterBypass

Question

我想在我的DocumentFilter 上有这样的方法

public void replaceUpdate(int offset, int length, String text) {
        try {
            super.replace(byPass, offset, length, text, null);
        } catch (BadLocationException ex) {
            //error
        }
}

目前，为了获得FilterBypass的实例（通过上面的方法），我需要从重写的方法insertString:中获得

private FilterBypass byPass;
@Override
    public void insertString(DocumentFilter.FilterBypass fb,
            int offset, String string, AttributeSet att)
            throws BadLocationException {
        byPass = fb;
        //some stuff here
        super.insertString(fb, offset, string, att);
    }

但这给我带来了一些问题。有人能提出一些不同的方法来获得FilterBypass吗？我找不到以不同方式引用FilterBypass的方法。

如果我要推翻它的方法，它应该如何？

Answer 1

例如，这里有一个带DocumentFilter的SSCCE，它可以防止用户在文档中键入数字，但允许Swing Timer这样做。

import java.awt.event.*;
import java.awt.event.ActionListener;
import javax.swing.*;
import javax.swing.text.*;
public class DocFilterPanel extends JPanel {
   private JTextArea textArea = new JTextArea(12, 50);
   private MyDocFilter myDocFilter = new MyDocFilter();
   public DocFilterPanel() {
      ((PlainDocument) textArea.getDocument()).setDocumentFilter(myDocFilter);
      int vsbPolicy = JScrollPane.VERTICAL_SCROLLBAR_ALWAYS;
      int hsbPolicy = JScrollPane.HORIZONTAL_SCROLLBAR_AS_NEEDED;
      add(new JScrollPane(textArea, vsbPolicy , hsbPolicy));
      int timerDelay = 1000;
      new Timer(timerDelay , new ActionListener() {
         @Override
         public void actionPerformed(ActionEvent e) {
            myDocFilter.setFilter(false);
            textArea.append("12345n");
            myDocFilter.setFilter(true);
         }
      }).start();
   }
   private static void createAndShowGui() {
      DocFilterPanel docFilterPanel = new DocFilterPanel();
      JFrame frame = new JFrame("DocFilterTest");
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.getContentPane().add(docFilterPanel);
      frame.pack();
      frame.setLocationByPlatform(true);
      frame.setVisible(true);
   }
   public static void main(String[] args) {
      SwingUtilities.invokeLater(new Runnable() {
         public void run() {
            createAndShowGui();
         }
      });
   }
}
class MyDocFilter extends DocumentFilter {
   private static final String REMOVE_REGEX = "\d";
   private boolean filter = true;
   public boolean isFilter() {
      return filter;
   }
   public void setFilter(boolean filter) {
      this.filter = filter;
   }
   @Override
   public void insertString(FilterBypass fb, int offset, String text,
         AttributeSet attr) throws BadLocationException {
      if (filter) {
         text = text.replaceAll(REMOVE_REGEX, "");
      }
      super.insertString(fb, offset, text, attr);
   }
   @Override
   public void replace(FilterBypass fb, int offset, int length, String text,
         AttributeSet attrs) throws BadLocationException {
      if (filter) {
         text = text.replaceAll(REMOVE_REGEX, "");
      }
      super.replace(fb, offset, length, text, attrs);
   }
}

Answer 2

我喜欢@hovercraft的解决方案，但它给我带来了并发问题。我通过同步文本区域上的过滤器切换来解决这个问题。像这样：

synchronized (textArea) {
    myDocFilter.setFilter(false);
    textArea.append("12345n");
    myDocFilter.setFilter(true);
}