我是java的新手,我只是想做一个简单的JFrame,通过JtextFields输入两个数字,求和并通过JLabel返回答案…但是它并没有做它应该做的事情,这是我的代码:
import javax.swing.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ComponentEvent;
import java.awt.event.ComponentListener;
import java.util.*;
public class gUi extends JFrame {
private JLabel lbl;
private JLabel lbl2;
private JLabel lbl3;
private JTextField tb;
private JTextField tb1;
private int num1;
private int num2;
public gUi(){
super("Sum Dialog");
setLayout(new FlowLayout());
lbl = new JLabel("1st Number:");
add(lbl);
tb = new JTextField(15);
add(tb);
tb.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event){
num1 = Integer.parseInt(tb.getText());
}
});
lbl2 = new JLabel("2nd Number");
add(lbl2);
tb1= new JTextField(15);
tb1.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event ){
num2= Integer.parseInt(tb1.getText());
}
});
add(tb1);
int sum= num1+num2;
String ssum = Integer.toString(sum);
lbl3 = new JLabel();
lbl3.setText(ssum);
add(lbl3);
}
}
import java.awt.*;
import javax.swing.*;
public class Main {
public static void main(String[] args) {
gUi g =new gUi();
g.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
g.setVisible(true);
g.setSize(180, 160);
}
}
它编译正常,但不显示sum通过JLabel当我放一些整数通过Textfields字段…我有这个问题一个星期,并尝试了不同的事情,我知道到目前为止,但问题仍然存在…
请看下面的代码(包括注释):
import java.awt.FlowLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
/**
* Shows a Stage that has two text Fields
*
*/
@SuppressWarnings("serial")
public class UserInterface extends JFrame {
private JLabel label1;
private JLabel label2;
private JLabel label3;
private JTextField textField1;
private JTextField textField2;
/**
* Constructor
*/
public UserInterface() {
super("Sum Dialog");
// Layout
setLayout(new FlowLayout());
// 1st JLabel
label1 = new JLabel("1st Number:");
add(label1);
textField1 = new JTextField(15);
add(textField1);
// 2 second JLabel
label2 = new JLabel("2nd Number");
add(label2);
textField2 = new JTextField(15);
add(textField2);
// 3 third label
label3 = new JLabel();
label3.setSize(200, 30);
add(label3);
JButton button = new JButton("Calculate");
button.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
// calculate the sum when the Button is pressed
int sum = Integer.parseInt(textField2.getText()) + Integer.parseInt(textField2.getText());
label3.setText(Integer.toString(sum));
}
});
add(button);
}
/**
* Main method of the application
*
* @param args
*/
public static void main(String[] args) {
UserInterface main = new UserInterface();
main.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
main.setVisible(true);
main.setSize(180, 160);
}
}
您已经创建了一个JLabel并将其初始值设置为0(因为最初num1 &Num2是0)。你需要做的是刷新JLabel(realculate &;
。
private void updateSum() {
lbl3.setText(String.valueOf(num1+num2));
}
并在textfield 1
的action listener中调用它tb.addActionListener(new ActionListener()
{
public void actionPerformed(ActionEvent event){
num1 = Integer.parseInt(tb.getText());
updateSum();
}
});
and
tb1.addActionListener(new ActionListener(){
public void actionPerformed(ActionEvent event ){
num2= Integer.parseInt(tb1.getText());
updateSum();
}
});
你不应该在你的文本域上放置动作监听器(当然,你可以;但这里还有其他选项)。
你可以添加一个按钮到你的框架,也许是文本"add"。每当按钮被点击时,你获取这两个值,并添加它们;然后把它们推到第三个文本框。
到目前为止,你的代码只计算一次0+0的和;调用构造函数时。相反,您必须确保此计算"稍后"发生-当用户要求它发生时!
但是要记录:如果您将相同的操作侦听器放在文本字段上,那也可以工作。如果该操作监听器只是简单地获取两个标签,将它们相加,并将总和放入字段3