java - why cannot read int value from JTextField

问题描述

JTextField t1 = new JTextField(' ');String a = t1.getText(); int intA = Integer.parseInt(a); System.out.println(intA);

Error

java.lang.NumberFormatException: For input string: '1 '

附上我的代码

public class Testing extends JPanel { public int s; public Testing() {JPanel p = new JPanel();JTextField t1 = new JTextField(' ');JTextField t2 = new JTextField(' ');JTextField t3 = new JTextField(' ');JButton b3 = new JButton('result');p.add(t1);p.add(t2);p.add(t3);p.add(b3);add(p);b3.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) {try { String a = t1.getText(); int intA = Integer.parseInt(a); System.out.println(intA); // String b = t2.getText(); //t3.setText(a+'');} catch (NumberFormatException ignored) { System.out.println(ignored);} }}); } public static void main(String... arg) {Testing p = new Testing();JFrame frame = new JFrame();frame.add(p);frame.setLocationRelativeTo(null);frame.pack();frame.setVisible(true); }}

问题解答

//导包。import javax.swing.*;import java.awt.event.*;

class JTextFieldDemo{

public static void main(String[] args){ JFrame jf = new JFrame();//创建窗体框架 jf.setTitle('我的标题');//设置窗体标题 jf.setBounds(400,500,300,200);//设置窗体在屏幕上出现的位置及大小 jf.setVisible(true);//设置窗体可见JPanel jp = new JPanel();//创建JPanel组件 jf.setContentPane(jp);//将JPanel组件添加到JFrame窗体中JButton jb = new JButton('转到');//创建JButton按钮组件 jp.add(jb);//将JButton组件添加到JPanel中JTextField jtf = new JTextField(10);//创建JTextField jp.add(jtf);//将JTextField添加到JPanel中 jb.addActionListener(new ActionListener()//给JButtona按钮添加点击事件 {public void actionPerformed(ActionEvent e){ String a =jtf.getText(); int IntA = Integer.parseInt(a); System.out.println(IntA);} });}

}

综上所述：楼主出现如上问题是因为jtf.getText();方法应该在输入内容后才让它执行，而楼主所示的代码却让它在运行时就执行，所以会报错。（个人拙见，嘿嘿）

谢谢@Sjs_k 的答案

把 JTextField t1 = new JTextField(''); 改去 JTextField t1 = new JTextField(5); 就行了