package edu.jiangxin.apktoolbox.swing.extend;
   
   import javax.swing.text.*;
   
   /**
    * 实现JTextfield只能输入数字并限制长度
    * 
    * @author jiangxin
    * @author 2019-03-24
   *
   */
  public class NumberPlainDocument extends PlainDocument {
  
      private static final long serialVersionUID = 1L;
  
      private int limit;
  
      public NumberPlainDocument(int limit) {
          super();
          this.limit = limit;
      }
      
      @Override
      public void insertString(int offset, String str, AttributeSet attr) throws BadLocationException {
          if (str == null) {
              return;
          }
          if ((getLength() + str.length()) <= limit) {
  
              char[] upper = str.toCharArray();
              int length = 0;
              for (int i = 0; i < upper.length; i++) {
                  if (upper[i] >= '0' && upper[i] <= '9') {
                      upper[length++] = upper[i];
                  }
              }
              super.insertString(offset, new String(upper, 0, length), attr);
          }
      }
  }