Java JFrame使框架获得两个数字的总和。不工作！ [英] Java JFrame Making a Frame to get sum of two numbers. Not Working!

问题描述

package com.testing.Test;

import java.awt。*;

import javax.swing。*;



public class Test扩展JFrame {

JLabel no1 = new JLabel（Number 1）;

JLabel no2 = new JLabel（Number 2 ）;

JLabel sum = new JLabel（Sum：，JLabel.CENTER）;

JTextField F1 = new JTextField（5）;

JTextField F2 =新的JTextField（5）;

JLabel no3 =新的JLabel（）;





public Test（）{

super（Test）;

Container container = getContentPane（）;

container.setLayout（new FlowLayout（ ））;

container.add（no1）;

container.add（F1）;

container.add（no2）;

container.add（F2）;

container.add（sum）;

container.add（no3）;

int n1 = Integer.parseInt（（F1.getText（）））;

int n2 = Integer.parseInt（（F2.getText（）））;

int no4 = n1 + n2;

String s1 = String.valueOf（no4）;

no3.setText（s1）;

}

public static void main（String []算法测试=新测试（）;

test.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）;

test.setSize（500， 400）;

test.setVisible（true）;

}



}



我应该做些什么更改，以便标签'no3'显示在两个文本字段中输入的两个数字的总和？

解决方案

< blockquote>您没有在JTextField中设置任何值。所以我添加了两行让你看到结果。

新的JTextField（5）; 

不用于设置字段值5.

 public JTextField（int columns） 
构造具有指定列数的新空TextField。创建默认模型，并将初始字符串设置为null。 
参数：
 columns  - 用于计算首选宽度的列数;如果列设置为零，则首选宽度将是组件实现自然产生的任何结果

 import java .awt *。 
 import javax.swing。*; 
 
公共类测试扩展JFrame {
 
 JLabel no1 = new JLabel（Number 1）; 
 JLabel no2 =新JLabel（2号）; 
 JLabel sum = new JLabel（Sum：，JLabel.CENTER）; 
 JTextField F1 = new JTextField（5）; 
 JTextField F2 = new JTextField（5）; 
 JLabel no3 = new JLabel（）; 
 
 public Test（）{
 super（Test）; 
 Container container = getContentPane（）; 
 container.setLayout（new FlowLayout（））; 
 container.add（no1）; 
 container.add（F1）; 
 container.add（no2）; 
 container.add（F2）; 
 container.add（sum）; 
 container.add（no3）; 
 F1.setText（5）; //在F1 
 F2.setText（5）中设置5; //在F2 
中设置5 int n1 = Integer.parseInt（（F1.getText（）））; // 5 
 int n2 = Integer.parseInt（（F2.getText（）））; // 5 
 int no4 = n1 + n2; // 10 
 String s1 = String.valueOf（no4）; 
 no3.setText（s1）; 
} 
 
 public static void main（String [] args）{
 Test test = new Test（）; 
 test.setDefaultCloseOperation（JFrame.EXIT_ON_CLOSE）; 
 test.setSize（500,400）; 
 test.setVisible（true）; 
} 
 
} 

package com.testing.Test;
import java.awt.*;
import javax.swing.*;

public class Test extends JFrame {
JLabel no1 = new JLabel("Number 1");
JLabel no2 = new JLabel("Number 2");
JLabel sum = new JLabel("Sum:",JLabel.CENTER);
JTextField F1 = new JTextField(5);
JTextField F2 = new JTextField(5);
JLabel no3 = new JLabel();


public Test() {
super("Test");
Container container = getContentPane();
container.setLayout(new FlowLayout());
container.add(no1);
container.add(F1);
container.add(no2);
container.add(F2);
container.add(sum);
container.add(no3);
int n1 = Integer.parseInt((F1.getText()));
int n2 = Integer.parseInt((F2.getText()));
int no4 = n1 + n2;
String s1 = String.valueOf(no4);
no3.setText(s1);
}
public static void main(String[] args) {
Test test = new Test();
test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
test.setSize(500, 400);
test.setVisible(true);
}

}

What changes should I make to so that the label 'no3' shows sum of the two numbers entered in the two textfields?

解决方案

you didn't set any value in JTextField. so I added two lines to let you see the results. The

new JTextField(5);

is not used to set the field value 5.

public JTextField(int columns)
Constructs a new empty TextField with the specified number of columns. A default model is created and the initial string is set to null.
Parameters:
columns - the number of columns to use to calculate the preferred width; if columns is set to zero, the preferred width will be whatever naturally results from the component implementation

import java.awt.*;
import javax.swing.*;

public class Test extends JFrame {

	JLabel no1 = new JLabel("Number 1");
	JLabel no2 = new JLabel("Number 2");
	JLabel sum = new JLabel("Sum:", JLabel.CENTER);
	JTextField F1 = new JTextField(5);
	JTextField F2 = new JTextField(5);
	JLabel no3 = new JLabel();

	public Test() {
		super("Test");
		Container container = getContentPane();
		container.setLayout(new FlowLayout());
		container.add(no1);
		container.add(F1);
		container.add(no2);
		container.add(F2);
		container.add(sum);
		container.add(no3);
		F1.setText("5"); // set 5 in F1
		F2.setText("5"); // set 5 in F2
		int n1 = Integer.parseInt((F1.getText())); // 5
		int n2 = Integer.parseInt((F2.getText())); // 5
		int no4 = n1 + n2; // 10
		String s1 = String.valueOf(no4);
		no3.setText(s1);
	}

	public static void main(String[] args) {
		Test test = new Test();
		test.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		test.setSize(500, 400);
		test.setVisible(true);
	}

}

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