ボタンを押すと速度が加算されるものを作りたい

前提・実現したいこと

自作でボタンを押すと速度が加算されるものを作っています。しかしエラーが出てしまうのでなぜなのか教えていただきたいです。

コンパイルするとエラーが出ます

発生している問題・エラーメッセージ

Sample.javaのupvx()やdownvx()などの４つでそれぞれ同じエラーが出ます

Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
	at Sample.actionPerformed(Sample.java:66)
	at java.desktop/javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:1967)
	at java.desktop/javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2308)
	at java.desktop/javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:405)
	at java.desktop/javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:262)
	at java.desktop/javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:279)
	at java.desktop/java.awt.Component.processMouseEvent(Component.java:6636)
	at java.desktop/javax.swing.JComponent.processMouseEvent(JComponent.java:3342)
	at java.desktop/java.awt.Component.processEvent(Component.java:6401)
	at java.desktop/java.awt.Container.processEvent(Container.java:2263)
	at java.desktop/java.awt.Component.dispatchEventImpl(Component.java:5012)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2321)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
	at java.desktop/java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4919)
	at java.desktop/java.awt.LightweightDispatcher.processMouseEvent(Container.java:4548)
	at java.desktop/java.awt.LightweightDispatcher.dispatchEvent(Container.java:4489)
	at java.desktop/java.awt.Container.dispatchEventImpl(Container.java:2307)
	at java.desktop/java.awt.Window.dispatchEventImpl(Window.java:2764)
	at java.desktop/java.awt.Component.dispatchEvent(Component.java:4844)
	at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:772)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:721)
	at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:715)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:95)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:745)
	at java.desktop/java.awt.EventQueue$5.run(EventQueue.java:743)
	at java.base/java.security.AccessController.doPrivileged(AccessController.java:391)
	at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:85)
	at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:742)
	at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:203)

該当のソースコード

java
1//Sample.java
2import java.awt.*;
3import java.awt.event.*;
4import javax.swing.*;
5
6public class Sample extends JPanel implements ActionListener{
7    
8    static int xPanelSize;
9    static int yPanelSize;
10     
11    
12    double x,y,r,vx,vy,ax,ay;
13   BallPropagator b1;
14    Color c1;
15  
16     static JButton btn1 = new JButton("↑");
17       static JButton btn2 = new JButton("↓");
18       static JButton btn3 = new JButton("→");
19       static JButton btn4 = new JButton("←");
20    Sample(int xPanelSize, int yPanelSize){
21           this.xPanelSize = xPanelSize;
22                 this.yPanelSize = yPanelSize;
23          btn1.addActionListener(this);
24          btn1.setBounds(100,100,50,100);
25          
26          
27          btn2.addActionListener(this);
28          btn2.setBounds(100,50,50,100);
29          
30          
31          btn3.addActionListener(this);
32          btn3.setBounds(0,100,100,100);
33          
34          
35          btn4.addActionListener(this);
36          btn4.setBounds(200,100,100,100);
37          
38          
39          
40         
41      }
42          //イベント（タイマーによる呼び出し）が発生したときの処理
43    public void dctionPerformed(ActionEvent e){
44        
45        //ボールb1 の位置の更新
46        b1.xUpdate();
47        b1.yUpdate();
48        //ボールb1 の速度の更新
49        b1.vxUpdate();
50        b1.vyUpdate();
51        
52       
53        // 再描画
54        repaint();
55        
56    }
57    public void actionPerformed(ActionEvent e){
58        JButton selectedButton = (JButton)e.getSource();
59    if(selectedButton==btn1){
60        System.out.println("up");
61        b1.upvy();
62        
63        repaint();
64    }else if(selectedButton==btn2){
65        System.out.println("down");
66        b1.downvy();
67     
68        repaint();
69    }else if(selectedButton==btn3){
70        System.out.println("left");
71        b1.leftvx();
72    
73        repaint();
74    }else{
75        System.out.println("right");
76        b1.rightvx();
77      
78        repaint();
79    }
80    }
81      
82    public void paintComponent(Graphics g){
83        super.paintComponent(g);
84      
85        g.setColor(c1);
86        
87        g.fillOval((int)(b1.a(x) - b1.c(r)), (int)(b1.b(y) - b1.c(r)),
88                   (int)(2*b1.c(r)), (int)(2*b1.c(r)));
89        
90      
91       
92    }
93              
94              
95             
96    public static void main(String[] args) {
97        BallMain panel = new BallMain(640,480);
98        Sample sample=new Sample(640,480);
99       
100        BallPropagator.dt=0.1;
101        BallPropagator.o=5.0;
102      
103        JFrame frame = new JFrame();
104        
105      
106       
107          
108                  panel.setBackground(Color.white);
109                  panel.setPreferredSize(new Dimension(xPanelSize,yPanelSize));
110        panel.add(btn1);
111        panel.add(btn2);
112        panel.add(btn3);
113        panel.add(btn4);
114      
115        BallPropagator.xmin = 0;
116        BallPropagator.xmax = panel.xPanelSize;
117        BallPropagator.ymin = 0;
118        BallPropagator.ymax = panel.yPanelSize;
119        
120      
121        frame.add(panel);
122        frame.pack();
123//
124        frame.setTitle("反射するボール");
125        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
126        //frame.setResizable(true);
127        frame.setVisible(true);
128        
129       
130        Timer timer = new Timer(10, panel);
131        timer.start();
132       
133       
134    }
135}
136
137

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


public class BallMain extends JPanel implements ActionListener{
    
   static int xPanelSize;
    static int yPanelSize;
    
    double x,y,r,vx,vy,ax,ay;
    BallPropagator b1;
   
    Color c1;
   
    BallMain(int xPanelSize, int yPanelSize){
         this.xPanelSize = xPanelSize;
               this.yPanelSize = yPanelSize;
        
       
        b1 = new BallPropagator(10, 100, 100, 30, 40, 0, 9.8);
         /////////////////////////////////////////////
        c1=Color.black;
     
        /////////////////////////////////////////////
    }
    
 
    public void actionPerformed(ActionEvent e){
          
         
          b1.xUpdate();
          b1.yUpdate();
         
          b1.vxUpdate();
          b1.vyUpdate();
          
         
        
          repaint();
      }   
    public void paintComponent(Graphics g){
        super.paintComponent(g);
      
       
        g.setColor(c1);
        g.fillOval((int)(b1.a(x) - b1.c(r)), (int)(b1.b(y) - b1.c(r)),
                   (int)(2*b1.c(r)), (int)(2*b1.c(r)));
        
      
    }
}

java
1BallPropagator.java
2public class BallPropagator{
3   
4    public static double dt;
5    public static int xmin;
6    public static int xmax;
7    public static int ymin;
8    public static int ymax;
9    
10   
11    private double r;
12    private double x, y; 
13    private double vx, vy;
14    private double ax, ay;
15    public static double o;
16    double p=0.8;
17  
18
19  
20    BallPropagator(double r,double x,double y,double vx,double vy,double ax,double ay){
21        this.r=r;
22        this.x=x;
23        this.y=y;
24        this.vx=vx;
25        this.vy=vy;
26        this.ax=ax;
27        this.ay=ay;
28    }
29 
30    public void xUpdate() {
31        this.x = this.x + this.vx * dt;
32       
33        if(this.x < (double)xmin+this.r ){
34            // this.vx = ??????????
35            this.vx *= -p;
36            this.x = (double)xmin+this.r;
37        }else if((double)xmax-this.r < x ){
38            // this.vx = ??????????
39            this.vx *= -p;
40            this.x = (double)xmax-this.r;
41        }
42    }
43  
44    public void yUpdate() {
45        this.y = this.y + this.vy * dt;
46      
47        if(this.y < (double)ymin + this.r ){
48            // this.vy = ??????????
49            this.vy *= -p;
50            this.y = (double)ymin+this.r;
51        }else if((double)ymax-this.r < this.y ){
52            // this.vy = ??????????
53            this.vy *= -p;
54            this.y = (double)ymax-this.r;
55        }
56    }
57   
58    public void vxUpdate(){
59        
60        this.vx=this.ax*dt+this.vx;
61
62    }
63    
64    public void vyUpdate(){
65        this.vy=this.ay*dt+this.vy;
66    // ????????
67    // ????????
68}
69    public void upvy(){
70        this.vy=this.vy+this.o;
71    }
72    public void downvy(){
73        this.vy=this.vy-this.o;}
74    public void leftvx(){
75        this.vx=this.vx-this.o;}
76    public void rightvx(){
77        this.vx=this.vx+this.o;}
78  
79        
80        
81        
82        
83    public double a(double x){
84       return x=this.x;
85}
86     public double b(double x){
87           return x=this.y;
88    } public double c(double x){
89           return x=this.r;
90    }
91}

TN8001

2020/07/20 08:44

[Java - ボタンを押しても反応しないです｜teratail](https://teratail.com/questions/278736 [Java - ボタンを押すと速度が加算されるものを作りたい｜teratail](https://teratail.com/questions/278819 [Java - javaの関数が反応しない｜teratail](https://teratail.com/questions/279029 ３つとも同じコードに見えます。これは3人とも同じ課題に取り組んでいるということでしょうか？？（申し上げにくいのですがあまりにもひどいコードなので）とても課題とは思えず、同一人物の投稿かと思ったのですがそうではないのですね？

行動規範の内容に同意します

回答1件

Sampleのb1がどこでも初期化されていないから、ですね。

java
1public class Sample extends JPanel implements ActionListener{
2...
3   BallPropagator b1;
4...
5    public void actionPerformed(ActionEvent e){
6...
7        b1.upvy();

BallMainのb1は初期化されているようですが、BallMainを使っている場所が、みたらない。

java
1public class BallMain extends JPanel implements ActionListener{
2...
3    BallPropagator b1;
4...
5        b1 = new BallPropagator(10, 100, 100, 30, 40, 0, 9.8);