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文本框事件

摘要: 文本框事件

文本框要求：
要求该文本框只能输入数字，输入其他的报错并且弹出错误提示窗口。

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import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;
public class Textfield extends Applet implements ActionListener
{
TextField text1;
public void init()
{
text1 = new TextField(20);
add(new Label("输入数字: "));
add(text1);
text1.addActionListener(this);
}
public void actionPerformed(ActionEvent e)
{
if(e.getSource() == text1)
{
String isNum = text1.getText();
int len = isNum.length();
String n ="0123456789";
for(int i=0;i {
try{
String loneNum = isNum.substring(i,i+1);
if( n.indexOf(loneNum) == -1)
{
JOptionPane.showMessageDialog(this,"非法字

符"," 警告对框",JOptionPane.WARNING_MESSAGE);
text1.setText(null);
break;
}
}
catch(NumberFormatException ee)
{
System.out.println(ee);
}
}
}
}
}

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/**
*你应该监听键盘事件!!!
*/
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.JOptionPane;
public class Textfield extends Applet implements KeyListener
{
TextField text1;
public void init()
{
text1 = new TextField(20);
add(new Label("输入数字: "));
add(text1);
text1.addKeyListener(this);
}
public void keyPressed(KeyEvent e)
{
if("0123456789".indexOf(e.getKeyChar()+"")==-1)
{
JOptionPane.showMessageDialog(this,"非法字符"," 警告对框",JOptionPane.WARNING_MESSAGE);
text1.setText(null);return;
}
}
public void keyReleased(KeyEvent e)
{
if("0123456789".indexOf(e.getKeyChar()+"")==-1)
{
JOptionPane.showMessageDialog(this,"非法字符"," 警告对框",JOptionPane.WARNING_MESSAGE);
text1.setText(null);return;
}
}
public void keyTyped(KeyEvent e)
{}
}

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