如何控制一个JTextField中输入的字符（或数字）不超过15位？我是这样做的，高手过来瞧一眼！

Question

现在的问题是在我的这段代码里怎么判断我目前已经输入了15个字符，
我采用了这种方法，但是总有问题，就是当我录入超过15个字符后，我把刚才录入的内容清空（或删除几个)，这时还是不能录入字符，因为我定义的变量是类变量（Static变量），我刚才说的情况怎么判断呢？我的代码如下：public class JTelDocument extends PlainDocument
{
  public static int intCount = 0;
  //重载insertString方法，限制它只能输入0-9数字、"("、")"、"-"符号
  public void insertString(int index, String str, AttributeSet as) throws BadLocationException
  {
    if ((str == null) || (str.length() == 0))
    {
      intCount = 0;
      return;
    }
    if (intCount > 15)
      return;    char[] input = str.toCharArray(); //转化成字符数组
    int length = 0; //合法输入的数组长度
    for (int i = 0; i < input.length; i++)
    {
      char ch = input[i];
      if (ch >= '0' && ch <= '9')
      {
        input[length++] = ch;
        intCount++;
      }
      if (ch == '(' || ch == ')' || ch == '-')
      {
        input[length++] = ch;
        intCount++;
      }
    }
    super.insertString(index, new String(input, 0, length), as);
  }
}

Answer 1

用KeyListener就可以了~~~然后用一个整形来控制输入的长度，每输一个就判断一次

Answer 2

这是我自己写的一个类，希望对你有点参考价值：package myjava;import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;/**
 * <p>Title: Control of the text field!
 * <p>Description: In this text field,
 * if the key that you push is not a number,
 * it will can't be disposed in the field!
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: 科大恒星
 * @author 呉志強
 * @version 1.0
 */public class OnlyInputNumberField extends JTextField
{
  int givenLenght;
  /** If the key have been pushed it will have do something.
   * @param e The event of the key pushed.
   */
  public OnlyInputNumberField() {
    this.addKeyListener(new KeyAdapter() {      /**
       * This method it will judge
       * whether or not the key you pushed is one of the keys of number
       * @param e The key event that you input
       */
      public void keyTyped(KeyEvent e)
      {
        char c = e.getKeyChar();//Get name of the key that have been pushed.
        String textValue = OnlyInputNumberField.this.getText();
        int len = textValue.length();
        if (c =='\b')
        {
          textValue=textValue.substring(0,len);
          OnlyInputNumberField.this.setText(textValue);
        }
        else
        {
          if (c >= '0' && c <= '9')
            return;
          else
            e.consume();
        }
      }
    });
  }  public OnlyInputNumberField(int i)
  {
    givenLenght = i;    this.addKeyListener(new KeyAdapter()
    {
      /**
       * This method it will judge
       * whether or not the lenght is over the given lenght
       * @param e The key event that you push.
       */
      public void keyTyped(KeyEvent e)
      {
        char c = e.getKeyChar();//Get name of the key that have been pushed.
        String textValue = OnlyInputNumberField.this.getText();
        int len = textValue.length();
        if (c =='\b')
        {
          textValue=textValue.substring(0,len);
          OnlyInputNumberField.this.setText(textValue);
        }
        else
        {
            if (c >= '0' && c <= '9')
            {
              if (len < givenLenght) {
                //System.out.println("the number");
                return;
              }
              else
                e.consume();
            }
            else
              e.consume();
          }
        }
    });
  }}

Answer 3

String textValue = OnlyInputNumberField.this.getText();这是什么意思？从你的代码中看不出如何控制所输入的数字不超过某个数？请指点！谢谢了！

Answer 4

import javax.swing.*;
import javax.swing.text.AbstractDocument;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.DocumentFilter;
public class DocSizeFilter extends JFrame {
    public static final int MAX_SIZE = 10;
    private JTextField jtf;    public DocSizeFilter() {
        AbstractDocument aDoc;        jtf = new JTextField();
        aDoc = (AbstractDocument) jtf.getDocument();
        aDoc.setDocumentFilter(new SizeFilter(MAX_SIZE));
        getContentPane().add(jtf);
    }    public static void main(String[] args) {
        DocSizeFilter frame = new DocSizeFilter();
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(EXIT_ON_CLOSE);
        frame.pack();
        frame.setVisible(true);
    }    private class SizeFilter extends DocumentFilter {
        int maxSize;
        int size;        public SizeFilter(int maxSize) {
            this.maxSize = maxSize;
        }        public void insertString(FilterBypass fb, int offset, String string,
                                 AttributeSet attr) throws BadLocationException {
            size = fb.getDocument().getLength() + string.length();
            if (size < maxSize) {
                super.insertString(fb, offset, string, attr);
            }
        }        public void replace(DocumentFilter.FilterBypass fb, int offset,
                            int length,String text, AttributeSet attrs)
                throws BadLocationException {
            size = fb.getDocument().getLength() + text.length();
            if (size < maxSize) {
                super.insertString(fb, offset, text, attrs);
            }
        }
    }
}

Answer 5

private class SizeFilter extends DocumentFilter {                            
    int maxSize;                                                             
    int size;                                                                
    Pattern p = Pattern.compile("[0-9()-]");                                 
    Matcher m = p.matcher("");                                               
                                                                             
    public SizeFilter(int maxSize) {                                         
        this.maxSize = maxSize;                                              
    }                                                                        
                                                                             
    public void insertString(FilterBypass fb, int offset, String string,     
                             AttributeSet attr) throws BadLocationException {
        size = fb.getDocument().getLength() + string.length();               
        m.reset(string);                                                     
        if (size < maxSize && m.matches()) {                                 
            super.insertString(fb, offset, string, attr);                    
        }                                                                    
    }                                                                        
                                                                             
    public void replace(DocumentFilter.FilterBypass fb, int offset,          
                        int length,String text, AttributeSet attrs)          
            throws BadLocationException {                                    
        size = fb.getDocument().getLength() + text.length();                 
        m.reset(text);                                                       
        if (size < maxSize && m.matches()) {                                 
            super.insertString(fb, offset, text, attrs);                     
        }                                                                    
    }                                                                        
}                                                                            用这个替换上面那个 SizeFilter 可以完全达到你的要求

Answer 6

如果只是要求String的长度达到15的话,可以直接改写一个PlainDocument类:
        jTextFiled.setDocument(new PlainDocument(){
            public void insertString (int offset, String str, AttributeSet a) {
                try {
                    if (this.getLength() + str.length() > 15){
                        return;
                    }
                    else{
                        super.insertString(offset, str, a);
                    }
                }
                catch (Exception exp) {
                }
            }
        });
就可以了.我实验过,对于字母,数字还有符号都可以.
不过,之后出现了一个大BUG,我试验了很多方法,怀疑是SWING的问题,就是输入全角字符会导致之前输入的文字被删除.好象是自动的.不管是输入中文或者日文都一样.郁闷中