有沒有辦法從 Java GUI 中的單獨類調用方法？

Question

我正在為一個班級做一個項目。 該項目要求我創建 3 個類，一個父類和兩個子類，每個類有 3 個方法。 然后它要求我創建一個 GUI，該 GUI 將根據幾個字段（包括文本和單選按鈕）計算銷售稅。 在我的腦海中，如果單擊某個單選按鈕，我會調用我的方法運行，即如果單擊 Hybrid 按鈕，它將運行 Hybrid 類中的 toString。 有人可以幫我弄清楚如何做到這一點嗎？

package projecttwo;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import javafx.scene.control.ToggleGroup;
import javax.swing.BorderFactory;
import javax.swing.ButtonGroup;
import javax.swing.JButton;
import javax.swing.JFormattedTextField;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JRadioButton;
import projectTwo.Automobile;
import projectTwo.Electric;
import projectTwo.Hybrid;

/**
 * CMIS242
 * November 14, 2020
 * Sabrina Riley
 * This program computes the sales tax for a collection of automobiles
 */
public class ProjectTwo extends JFrame implements ActionListener {

    /**
     * @param args the command line arguments
     */
    //Variable declaration
    private String select;    
    private JFrame frame;
    private JPanel panel;
    private JLabel label, label2, label3, label4, label5;
    private JFormattedTextField mmText, salesText, mpgText, weightText, compute;
    private JButton button, button2, button3;
    private JRadioButton hybrid, electric, other;
    private ButtonGroup bg;
    private JPanel radioPanel;
    Automobile car = new Automobile();
    
    public ProjectTwo() {
        //initialize GUI
        frame = new JFrame();
        
        //HandlerClass handler = new HandlerClass();
        //add compute sales tax button
        button = new JButton("Compute Sales Tax");
        button.setBounds(0,100,150,50);
        add(button);
        button.addActionListener(this);
        
        
        //add display results button
        button2 = new JButton("Display Results");
        button2.setBounds(0,200, 150, 50);
        button2.addActionListener(this);
        
        //add clear fields button
        button3 = new JButton("Clear Fields");
        button3.setBounds(200,200, 150, 50);
        button3.addActionListener(this);
        
         
        //add text field to display results from compute sales button
        compute = new JFormattedTextField();
        compute.setBounds(200,100,150,50);
        compute.setEditable(false);
        
        //add all other text fields
        mmText = new JFormattedTextField();
        mmText.addKeyListener(null);
        //mmText.addActionListener(this);
        salesText = new JFormattedTextField();
        mpgText = new JFormattedTextField();
        weightText = new JFormattedTextField();       
        
        //add radio buttons to pick between hybrid, electric, and other
        hybrid = new JRadioButton("Hybrid", true);        
        electric = new JRadioButton("Electric", false);        
        other = new JRadioButton("Other", false);
        
        //group the radio buttons together
        bg = new ButtonGroup();
        bg.add(hybrid);
        bg.add(electric);
        bg.add(other);
        
        //arrange buttons vertically
        radioPanel = new JPanel();
        radioPanel.setLayout(new GridLayout(3,1));
        //radioPanel.setBounds(100,200,150,200);
        radioPanel.add(hybrid);
        radioPanel.add(electric);
        radioPanel.add(other);
        setContentPane(radioPanel);
        pack();
        
        
        //make them listen to clicks
        hybrid.addActionListener(this);
        electric.addActionListener(this);
        other.addActionListener(this);
        
        //label all text fields
        label = new JLabel("Make and Model");
        label.setBounds(0, 0, 100, 150);
        label2 = new JLabel("Sales Price");
        label3 = new JLabel("Automobile Type");
        label4 = new JLabel("Miles Per Gallon");
        label5 = new JLabel("Weight in Pounds");
 
        //implement panel with all labels, text fields, buttons, and radio buttons
        panel = new JPanel();
        panel.setBorder(BorderFactory.createEmptyBorder(30, 30, 10, 30));
        //panel.setLayout(GridLayout(0,2));
        panel.setLayout(new GridLayout(0,2));
        panel.setSize(500, 500);
        panel.add(label);
        panel.add(mmText);
        panel.add(label2);
        panel.add(salesText);
        panel.add(hybrid);
        panel.add(electric);
        panel.add(other);
        panel.add(label3);
        panel.add(mpgText);
        panel.add(label4);
        panel.add(weightText);
        panel.add(label5);
        panel.add(button);
        panel.add(compute);
        panel.add(button2);
        panel.add(button3);
        panel.add(radioPanel);

        //set frame dimensions
        frame.add(panel, BorderLayout.CENTER);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setTitle("Automobile Sales Tax Calculator");
        frame.pack();
        frame.setVisible(true);
    }
    
    
    
    @Override
    public void actionPerformed(ActionEvent e) {
        String user = mmText.getText();
        String sales = salesText.getText();
        String mpg = mpgText.getText();
        String weight = weightText.getText();
        this.clearFields();
        e.getActionCommand();
        
        if(e.getSource()==hybrid) {
            System.out.println("car is a hybrid");
        } else if (e.getSource()==electric){
            System.out.println("car is electric");
        } else
            System.out.println("car is basic");
        
        System.out.println(", " + user + sales + ", " + weight + ", " + mpg);
        
        //throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    public void clearFields() { 
        mmText.setText(null);
        salesText.setText(null);
        mpgText.setText(null);
        weightText.setText(null);
        compute.setText(null);
        hybrid.setSelected(false);
        electric.setSelected(false);
        other.setSelected(false);
    }

    public static void main(String[] args) {
        // TODO code application logic here
        new ProjectTwo();  
    }
}

package projectTwo;

/**
 * CMIS242
 * November 14, 2020
 * Sabrina Riley
 * This program computes the sales tax for a collection of automobiles
 */
public class Automobile {
    protected String make;
    protected String model;
    protected double salesPrice;
    protected double salesTax;
    
    public Automobile() {
        make = "brand";
        model = "type";
    }
    //A constructor that allows the make and purchase price to be initialized
    public Automobile(String make, String model, double salesPrice, double salesTax) {
        this.make = make;
        this.model = model;
        this.salesPrice = salesPrice;
        this.salesTax = salesTax;
    }

    //A method that returns the base sales tax computed as 5% of the sales price
    public double salesTax() {
        salesTax = salesPrice * 0.05;
        return salesTax;
    }

    //A toString method that returns a string containing the make and model of the     
    //automobile, the sales price, and the sales tax
    public String toString() {
        return make + model + salesTax;
    }
}

package projectTwo;

/**
 * CMIS242
 * November 14, 2020
 * Sabrina Riley
 * This program computes the sales tax for a collection of automobiles
 */
public class Hybrid extends Automobile {
    protected int mpg;
    protected double discount;
    //A constructor that allows the make and purchase price to be initialized
    public Hybrid(int mpg) {
        super();
        
        mpg = 0;
    }
    
    public Hybrid(String make, String model, double salesPrice, double salesTax, int mpg) {
        super(make, model, salesPrice, salesTax);
        this.mpg = mpg; 
    }

    //A method that returns the base sales tax computed as 5% of the sales price
    @Override
    public double salesTax() {
        if (mpg  < 40) 
            discount = salesTax + 100;
        else 
            discount = salesTax + 100 + (mpg * 2);
        return discount;      
    }

    //A toString method that returns a string containing the make and model of the     
    //automobile, the sales price, and the sales tax
    @Override
    public String toString() {
        return make + model + salesPrice + discount + discount;
    }    
}

Answer 1

以我的拙見，如果正確理解您想要實現的目標，您必須在 ProjectTwo 的構造函數中創建一個“Hybrid”類的實例，就像：
在那里聲明變量，你有所有的變量聲明，只是為了讓它成為全局的：

private Hybrid hybr;

在構造函數中創建實例：

hybr = new Hybrid("make", "hybrid's model", 20500.50, 12.5, 5);

然后在您的代碼中，您需要使用 Hybrid 的方法調用您的方法，在本例中為hybr.toString() 。