Question

所以我有一个叫做方程式的方法，应检查是否有任何值为0，但它们不是？据我所知，当我用单选按钮选择它们时，它们根本不运行。为什么是这样？它只是将位移值打印为0. Idk在这做什么？感谢所有帮助！

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
//import java.applet.Applet;

public class RadioButton extends JPanel {
//Values that can be entered at the beginning, the code will explain to you what this means and how you can find the other values
    //If you don't know one of the values, make it 0

    int xDisplacement = 0; 
    int xVAvg = 8;
    int xTime = 8 ;

    public void equations() {
         if (xDisplacement == 0) {
             //solve for displacement
                int xDisplacement = xVAvg * xTime; 
         }
         if (xVAvg == 0) {
             int xVAvg = xDisplacement / xTime; 
         }
         if (xTime == 0) {
             int xTime = xDisplacement / xVAvg; 
         }
     }





    static JFrame frame;

   JLabel pic;
   RadioListener myListener = null;
   protected JRadioButton displacement;
   protected JRadioButton vAvg; 
   protected JRadioButton time;
   public RadioButton() {



       // Create the radio buttons
       displacement = new JRadioButton("Displacement");
       displacement.setMnemonic(KeyEvent.VK_N);
       displacement.setActionCommand("displacement");
        //Displacement Button, set to automatically be clicked

       vAvg = new JRadioButton("Average Velocity");
       vAvg.setMnemonic(KeyEvent.VK_A);
       vAvg.setActionCommand("averagevelocity");
        //Acceleration Button

       time = new JRadioButton("Change in time");
       time.setMnemonic(KeyEvent.VK_S);
       time.setActionCommand("deltaT");
        //The change in time button


       // Creates the group of buttons
       ButtonGroup group = new ButtonGroup();
       group.add(displacement);
       group.add(vAvg);
       group.add(time);

              myListener = new RadioListener();
                displacement.addActionListener(myListener);
                vAvg.addActionListener(myListener);
                time.addActionListener(myListener);


      // Set up the picture label
       pic = new JLabel(new ImageIcon(""+"numbers" + ".jpg"));          //Set the Default Image

       pic.setPreferredSize(new Dimension(177, 122)); 


       // Puts the radio buttons down
       JPanel panel = new JPanel();
       panel.setLayout(new GridLayout(0, 1));
       panel.add(displacement);
       panel.add(vAvg);
       panel.add(time);


       setLayout(new BorderLayout());
       add(panel, BorderLayout.WEST);
       add(pic, BorderLayout.CENTER);
       setBorder(BorderFactory.createEmptyBorder(40,40,40,40));
   } 



   //Listening to the buttons
   class RadioListener implements ActionListener { 
       public void actionPerformed(ActionEvent e) {
           pic.setIcon(new ImageIcon(""+e.getActionCommand() + ".jpg"));
    equations();
    running();


       }
    }
   public static void main(String s[]) {
        frame = new JFrame("∆x = Vavg * time");
        frame.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {System.exit(0);}
        });

        frame.getContentPane().add(new RadioButton(), BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
   }


     public void running() {
        if ( displacement.isSelected()) {
            //Option 1
            System.out.println("The distance traveled on the x axis in meters is " + xDisplacement);
            System.out.println("You can find the Average Velocity by dividing this number by time or find the time by dividing this number by the Average Velocity");
            System.out.println("----------> ");
            System.out.println("^  " + xDisplacement ); 
            }
        if ( vAvg.isSelected()) {
            //Option 2 
            System.out.println("The average velocity in Meters per Second is " + xVAvg);
            System.out.println("You can find the displacement by multiplying the time and this number together or to find the time, just divide the displacement by this number");
            System.out.println("----------> ");
            System.out.println("^  " + xVAvg ); 
        }

        if (time.isSelected()) {
            //Option 3
            System.out.println("The time in seconds is " + xTime);
            System.out.println("You can find the displacement by multiplying the velocity times this number or you can find the average velocity by dividing the displacement by this number");
            System.out.println("----------> ");
            System.out.println("^  " + xTime ); 
        }
        }



   }

Answer 1

您正在创建新的块本地值，而不是修改RadioButton的属性。

public class RadioButton extends JPanel {
    int xDisplacement = 0; 

    public void equations() {
         if (xDisplacement == 0) {
             // This is a **NEW** `xDisplacement`, visible only
             // within these curly brackets, "shadowing" the
             // instance property `xDisplacement`
             int xDisplacement = xVAvg * xTime;
         }

// etc.

只需删除int语句中的if即可修改该属性。

您的IDE可能会警告您，您正在隐藏某个属性，顺便说一句。

    public void equations() {
         if (xDisplacement == 0) {
             xDisplacement = xVAvg * xTime;
         }
// etc.

当单选按钮选中时，为什么不解决方程？

1 个答案: