JTextField只能输入数字与小数位数的控制

实现JTextField只能输入数字，并且控制小数的位数与数字的总长度

 

import java.awt.Container;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.math.BigDecimal;
import javax.swing.JFrame;
import javax.swing.JTextField;
import javax.swing.text.AttributeSet;
import javax.swing.text.BadLocationException;
import javax.swing.text.PlainDocument;

/**
 * 只能输入数字
 * @author 心星
 */
public class Txtonlynumber {

	public Txtonlynumber() {
		JFrame f = new JFrame("Txtonlynumber");
		Container contentPane = f.getContentPane();
		JTextField salary = new JTextField(50);
		salary.setDocument(new NumOnlyDocument());

		contentPane.add(salary);
		f.pack();
		f.setVisible(true);
		f.addWindowListener(new WindowAdapter() {
			public void windowClosing(WindowEvent e) {
				System.exit(0);
			}
		});
	}

	public static void main(String[] args) {
		new Txtonlynumber();

	}

	class NumOnlyDocument extends PlainDocument {
		private static final long serialVersionUID = 1001689415662878505L;
		
		int maxLen;  //最长字符长度
		int decimalLen; //小数位数
		
		public NumOnlyDocument() {
			this(2,13);
		}
		
		public NumOnlyDocument(int newDecimalLen, int newMaxLen) {
			super();
			decimalLen = newDecimalLen;
			maxLen = newMaxLen;
		}
		
		public void insertString(int offset, String inStr, AttributeSet attrSet) 
			throws BadLocationException {
			// 获得输入框有效值
			String numStr = getText(0, offset) + inStr + getText(offset, getLength() - offset);
			System.out.println("inStr===" + inStr + ",offset==" + offset 
				+ ",getLength()=" + getLength() + ",value=" + numStr);
			// 校验字符长度限制
			if (getLength() + inStr.length() > maxLen) {
				return;
			}
			// 校验是否是有效数字
			try {
				new BigDecimal(numStr);
			} catch (NumberFormatException e1) {
				return;
			}
			// 校验小数位数限制
			int indexNum = numStr.indexOf(".");
			if (indexNum > 0) {
				int len = numStr.substring(indexNum + 1).length();
				if (len > decimalLen) {
					return;
				}
			}
			super.insertString(offset, inStr, attrSet);
		}
	}

}