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I need a bit of help. I'm just after coming back to programming after being made unemployed.

I'm trying to learn Java and I have run into a difficulty.

The problem is that I want to call a method that should ask the user for an input by pressing a button. This will return the chouce back to the class that called the method.

    public class ButtonMain {
        private static CreateButton cButton;

        public static void main(String[] args) {
            cButton = new CreateButton();
            cButton.launchButton();
            switch(cButton.getSelect()) {
                case 'a' : System.out.println("German Car");
                    break;
                case 'b' : System.out.println("Japanese Car");
                    break;
                default : System.out.println("Incorrect Car Selected");               
                    break;
            }
        }
    }

The rest of the code is as follows

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

public class CreateButton implements ActionListener {
    private JFrame mainFrame;
    private JLabel label1;
    private JButton button1;
    private JButton button2;
    private char select = ' ';

    public CreateButton() {
    }

    public void launchButton() {
        createFrame();
        createLabel();
        createButton1();
        createButton2();
    }

    private void createFrame() {
        mainFrame = new JFrame("Cars");
        mainFrame.setSize(200, 200);
        mainFrame.setLocation(300, 300);
        mainFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        mainFrame.setVisible(true);
        mainFrame.setPreferredSize(null);
        mainFrame.setLayout(new java.awt.GridLayout(3, 1));
    }

    private void createLabel() {
        label1 = new JLabel("Cars", SwingConstants.CENTER);
        label1.setSize(200, 100);
        mainFrame.getContentPane().add(label1, BorderLayout.CENTER);
    }

    public void createButton1() {
        button1 = new JButton("Mercedes");
        button1.setSize(200, 50);
        button1.addActionListener(this);
        mainFrame.getContentPane().add(button1, BorderLayout.CENTER);
    }

    private void createButton2() {
        button2 = new JButton("Lexus");
        button2.setSize(200, 50);
        button2.addActionListener(this);
        mainFrame.getContentPane().add(button2, BorderLayout.CENTER);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button1) {
            select = 'a';
            System.out.println(select);
        }
        else if (e.getSource() == button2) {
            select = 'b';
            System.out.println(select);
        }
    }

    public char getSelect() {
        return select;
    }
}

What is happening is that the output should read a or b and then whether German or Japanese cars was selected but i'm getting the incorrect car selected.

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2 回答 2

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问题是在调用 main 时您将没有选择信息。最好在 ActionListener 本身中处理这个问题。

或者

一旦实现了一个 Swing 组件，所有可能影响或依赖于该组件状态的代码都应该在事件调度线程中执行。

于 2012-08-13T22:27:24.970 回答
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代码工作正常。它是您的代码正在运行，没有任何东西可以阻止它。cButton.launchButton()简单地显示框架和运行后的代码。由于select已初始化为空格字符，因此程序启动时会打印“Incorrect Car Selected”。您对按钮的操作正常。您的 switch 语句应该在actionPerformed方法中。

    public void actionPerformed(ActionEvent e) {
    if (e.getSource() == button1) {
        select = 'a';
        System.out.println(select);
    } else if (e.getSource() == button2) {
        select = 'b';
        System.out.println(select);
    }

    switch (getSelect()) {
    case 'a':
        System.out.println("German Car");
        break;
    case 'b':
        System.out.println("Japanese Car");
        break;
    default:
        System.out.println("Incorrect Car Selected");
    }

}
于 2012-08-13T22:31:09.087 回答