按钮和文本字段不会显示在Java中 [英] Button and textfield don't show up in Java

问题描述

对于学校，我必须在一个按钮和两个文本区域内制作一个JFrame。无论你在Textfield中放置什么，按下按钮时都必须进入textfield 2。当我运行程序时，我得到了代码，我应该看到textfields和按钮。无论出于何种原因，它都没有。

For school I had to make a JFrame and within that One button and Two textfields. Whatever you put in Textfield one have to get into textfield two when the button is pressed. I got the code to the point I should see the textfields and the button when i run the program. For whatever reason it doesn't.

我到目前为止：

package helloworld;

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

    public class HelloWorld extends JFrame {

        public static void main(String[] args) {

             JFrame frame = new HelloWorld();
             frame.setSize(400, 400);
             frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
             frame.setTitle("Hello World Button App");

             JPanel panel = new JPanel();
             frame.setContentPane(panel);
             fram.setVisible(true);
         }
       }

       class panel extends JPanel {

          public JButton btn1 = new JButton("Klick!");
          public JTextField txt1 = new JTextField(10);
          public JTextField txt2 = new JTextField(10);

          public panel() {
               add(btn1);
               add(txt1);
               add(txt2);
            }
          }

我还不能发布图片，但我会提供图片链接此处

I am not yet allowed to post images but I will provide a link to the picture down here

如果这个问题已经出现，我很抱歉，但我找不到类似的问题。
我是编程的新手，所以当我忘记了某些内容或写错了内容时，请不要对我大喊大叫！

I am sorry if this question allready exests but i couldnt's find a similar question. I am new to programming so please dont yell at me when I forgot something or wrote something wrong in it!

推荐答案

这里我修改了你的代码，但是以类似的方式做了。
我不会延长 JFrame ，除非我不想做一些有创意的事情，但你总是可以。

Here i have modified your code a bit, but did in a similar way. I won't extend JFrame until and unless i don't want to do something creative, but you always CAN.

你已经扩展了 JFrame ，所以没有值得用调用方法frame.foo（）
，但只需 foo（），最重要的是 JFrame frame = new HelloWorld（），将不会感觉，如果你已经用 JFrame 扩展了你的课程：

You had already extended JFrame , so no worth of calling methods with frame.foo() but simply foo() , and most important JFrame frame = new HelloWorld() , will make no sense, if you have already extended you class with JFrame:

import javax.swing.*;

public class HelloWorld extends JFrame{

 public static void main(String[] args) {

          SwingUtilities.invokeLater(new Runnable() {
          public void run() {
          new HelloWorld().setVisible(true);
        }
    });

     }
    public  HelloWorld()
    {

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("Hello World Button App");

        panel pan= new panel();
        add(pan.panel);
        pack();
        setVisible(true);
    }
   }

   class panel {

      private JButton btn1 = new JButton("Klick!");
      private JTextField txt1 = new JTextField(10);
      private JTextField txt2 = new JTextField(10);
      JPanel panel;
      public panel() {
           panel = new JPanel();
           panel.add(btn1);
           panel.add(txt1);
           panel.add(txt2);
        }
      }

此外，您还可以延长面板类 JPanel ：

Also, you can also extend your panel class with JPanel :

 public  HelloWorld()
    {

        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setTitle("Hello World Button App");

          panel pan= new panel();
         add(pan);
         pack();
         setVisible(true);
    }
   }

   class panel extends JPanel {

      private JButton btn1 = new JButton("Klick!");
      private JTextField txt1 = new JTextField(10);
      private JTextField txt2 = new JTextField(10);

      public panel() {

           add(btn1);
           add(txt1);
           add(txt2);
        }
      }

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