java - 在java中使用JPanel时，如何将一个类中的用户输入数据显示到另一个类中

Question

我在这方面遇到了一些困难。基本上，我希望用户在一个 Java 类中输入名称，并在另一个类中显示该数据。我尝试使用 gets 但我总是得到“null”。另外，如果我想从我的类(class)(示例)中获取一个 int 以在我的第二个类(class)中显示，您会如何执行此操作。基本上是一样的吗？

这是一个例子来说明我的意思

一级

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

public class Exampl extends JFrame implements ActionListener {

    JLabel intro = new JLabel("Welcome What is your name?");
    JTextField answer = new JTextField(10);
    JButton button = new JButton("Enter");
    final int WIDTH = 330;
    final int HEIGHT = 330;
    JLabel greeting = new JLabel("");
    JButton next =new JButton("Next");
     String name = answer.getText();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }


    public Exampl() {
        super("Welcome");
        setSize(WIDTH, HEIGHT);
        setLayout(new FlowLayout());
        add(intro);
        add(answer);
        add(button);
        add(greeting);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        button.addActionListener(this);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent event) {
        Object source = event.getSource();
        if (source == button) {
             String greet = "Hello there" + name;
             greeting.setText(greet);
              add(next);
       next.addActionListener(this);

           if(source==next)
            dispose();
            new Hello();
        }

    }


      public static void main(String[] args) {
        Exampl frame= new Exampl();
        frame.setVisible(true);

    }
}

二等

import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Hello extends JFrame implements ActionListener {
    String name;
    JLabel hi = new JLabel("Nice to see you "+name);
    JButton button = new JButton("Enter");
    final int WIDTH = 330;
    final int HEIGHT = 330;
    JLabel greeting = new JLabel("");
    JButton next =new JButton("Next");

    public Hello() {
        super("Welcome");
        setSize(WIDTH, HEIGHT);
        setLayout(new FlowLayout());
        add(hi);
        add(button);
        add(greeting);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        button.addActionListener(this);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent event) {
        Object source = event.getSource();
        if (source == button) {
             String greet = "example " + name;
             greeting.setText(greet);
              add(next);
        }
    }

    public static void main(String[] args) {
        Exampl frame= new Exampl();
        frame.setVisible(true);           
    }        
}

Answer 1

我给你的建议:

1. 不要扩展 JFrame，而是扩展 JPanel。请参阅:Extends Frame vs creating it inside the program和 Why shouldn't you extend JFrame and other components
2. 不要使用多个JFrame。请参阅The use of multiple JFrames, good / bad practice? (BAD)相反，您可能想尝试使用 Card Layout或JDialog s

What do you mean by extend? do you mean "public class Hello extends Exampl"? I'm new to java so I don't know much.

根据对另一个答案的评论，您可能希望首先在控制台应用程序中学习基础知识，然后再进入 GUI 应用程序，这会增加您的程序的复杂性，从而增加您的学习的复杂性。

I'm planning on doing a project where I add the inputted name and a random int into a file so I can store it. Or would it make more sense to add that code into the same class?

根据该注释，您可以创建一个公共(public)方法，该方法以您需要的格式返回 JTextField 中的值，然后从其他类调用该方法，例如:

public String getUserName() {
    return userNameField.getText();
}

public int getDigit() {
    try {
        return Integer.parseInt(digitField.getText());
    } catch (NumberFormatException nfe) {
        nfe.printStackTrace();
    }
    return -1; //In case it's not a number, or return 0, or whatever you need
}

//------In another class------//

int digit = object1.getDigit(); //Where object1 is an instance of the other class where those methods are defined