高手HELPME ~~怎么控制JTextField中输入字符串长度?

Question

怎么控制JTextField中输入字符串长度?
例如:
控制输入5个字符长度..怎么做?

Answer 1

import javax.swing.*;
import javax.swing.text.*;public class PlainDocumentDemo extends JFrame {
    private JTextField txt;    public PlainDocumentDemo() {
        txt = new JTextField();
        txt.setDocument(new PlainDocument() {
            public void insertString(int offset,
                                     String str, 
                                     AttributeSet attSet) 
            throws BadLocationException{
                boolean allDigit = true;
                for(int i=0; str!=null&&i<str.length(); i++){
                    char c = str.charAt(i);
                    //System.out.println(c);
                    if(c>'9' || c<'0'){
                        allDigit = false;
                        break;
                    }
                }
                if(allDigit){
                    super.insertString(offset,str,attSet);
                }
            }
        });
        
        this.setSize(400,300);
        this.add(txt);
        this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        this.setVisible(true);
        //this.pack();
    }    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new PlainDocumentDemo();
    }}//这段程序只允许输入数字，方法稍微改一下应该就能满足你的要求了，另外的方法不是很清楚