numberfield.java

用于传感器网络的节点操作系统 TinyOS 结构设计非常有意思

package net.tinyos.tinydb;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.text.*;


/** NumberField is a JTextField that 
    constrains its contents to contain
    only numbers.

    @author Sam Madden ([e-mail])
*/
public class NumberField extends JTextField {
    public NumberField(int cols) {
	super(cols);
    }
    protected Document createDefaultModel() {
	return new NumberDocument();
	}
    class NumberDocument extends PlainDocument
    {
	public void insertString(int offs, String str, AttributeSet a) throws BadLocationException {
	    boolean ok = true;
	    for (int i = 0; i < str.length(); i++) {
		if (!Character.isDigit(str.charAt(i))) ok = false;
	    }
	    if (ok) super.insertString(offs,str,a);
	}
    }	
}