0

My basket returns error messages when I try to move it. keylistener prints out keys like usual and I looked for usual errors but I always get the same error message during the run.

keyPressed 39
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at view.DrawingPanel.right(DrawingPanel.java:65)
    at view.GameUI.keyPressed(GameUI.java:74)
    at java.awt.Component.processKeyEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Window.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)
keyPressed 37
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at view.DrawingPanel.left(DrawingPanel.java:60)
    at view.GameUI.keyPressed(GameUI.java:71)
    at java.awt.Component.processKeyEvent(Unknown Source)
    at java.awt.Component.processEvent(Unknown Source)
    at java.awt.Container.processEvent(Unknown Source)
    at java.awt.Window.processEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.KeyboardFocusManager.redispatchEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.dispatchKeyEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.preDispatchKeyEvent(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.typeAheadAssertions(Unknown Source)
    at java.awt.DefaultKeyboardFocusManager.dispatchEvent(Unknown Source)
    at java.awt.Component.dispatchEventImpl(Unknown Source)
    at java.awt.Container.dispatchEventImpl(Unknown Source)
    at java.awt.Window.dispatchEventImpl(Unknown Source)
    at java.awt.Component.dispatchEvent(Unknown Source)
    at java.awt.EventQueue.dispatchEventImpl(Unknown Source)
    at java.awt.EventQueue.access$500(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.awt.EventQueue$3.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.awt.EventQueue$4.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source)
    at java.awt.EventQueue.dispatchEvent(Unknown Source)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.pumpEvents(Unknown Source)
    at java.awt.EventDispatchThread.run(Unknown Source)

the indicated error lines are for basket.setMoveL(true); in left & right in DrawingPanel and panel.left(); & right respectively

Here is my code for GameUI

package view;

import java.awt.BorderLayout;
import java.awt.EventQueue;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.border.EmptyBorder;
import javax.swing.GroupLayout;
import javax.swing.GroupLayout.Alignment;
import java.awt.Color;

public class GameUI extends JFrame implements KeyListener{

    private JPanel contentPane;
    private DrawingPanel panel;

    /**
     * Launch the application.
     */
    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            public void run() {
                try {
                    GameUI frame = new GameUI();
                    frame.setVisible(true);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }
        });
    }

    /**
     * Create the frame.
     */
    public GameUI() {
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setBounds(100, 100, 600, 400);
        contentPane = new JPanel();
        contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
        setContentPane(contentPane);

        panel = new DrawingPanel();
        panel.setBackground(Color.BLACK);
        GroupLayout gl_contentPane = new GroupLayout(contentPane);
        gl_contentPane.setHorizontalGroup(
            gl_contentPane.createParallelGroup(Alignment.LEADING)
                .addComponent(panel, GroupLayout.DEFAULT_SIZE, 574, Short.MAX_VALUE)
        );
        gl_contentPane.setVerticalGroup(
            gl_contentPane.createParallelGroup(Alignment.LEADING)
                .addComponent(panel, Alignment.TRAILING, GroupLayout.DEFAULT_SIZE, 351, Short.MAX_VALUE)
        );
        contentPane.setLayout(gl_contentPane);
        addKeyListener(this);
    }

    @Override
    public void keyPressed(KeyEvent e) {
        // TODO Auto-generated method stub
        // show keycode of pressed key:
         int k = e.getKeyCode();
        System.out.println("keyPressed " + k);

        //call direction left & right
        switch(k) {
        case 37:
            panel.left();
            break;
        case 39:
            panel.right();
            break;
        }
    }

    @Override
    public void keyReleased(KeyEvent e) {
        // TODO Auto-generated method stub

    }

    @Override
    public void keyTyped(KeyEvent e) {
        // TODO Auto-generated method stub

    }

}

And my code for the Drawing Panel

package view;

import java.awt.Graphics;
import java.util.ArrayList;
import javax.swing.JPanel;
import javax.swing.Timer;

import model.ControlElement;
import model.DrawingObject;

public class DrawingPanel extends JPanel {

    private ArrayList<DrawingObject> gameElements;

    private ControlElement basket;
    private ControlElement launcher;
    private Timer t;

    public DrawingPanel() {
        super();
        // within constructor create a list of Game elements that are drawingObjects
        gameElements = new ArrayList<DrawingObject>();

        //initialize repainting 
        t = new Timer(20, (e) -> repaint() );
        t.start();
    }

    @Override   
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);

        // paintComponent method
        if (basket == null) { //no basket is there yet so make one
            newBasket();
        }
        if (launcher == null) { //no launcher is there yet so make one
            newLauncher();
        }


        for (int i = gameElements.size()-1; i >= 0; i-- ) { // draw all game Elements
            gameElements.get(i).paintComponent(g);
        }
    }


    private void newBasket(){ //making a basket
        ControlElement basket = new ControlElement("basket.png", this, getWidth() / 2, getHeight() - 25);
        gameElements.add(basket);
    }

    private void newLauncher(){ // making a launcher
        ControlElement launcher = new ControlElement("launcher.png", this, 5, getHeight() - 55);
        gameElements.add(launcher);
    }


    public void left() {
        basket.setMoveL(true);
        basket.move();
    }

    public void right() {
        basket.setMoveL(false);
        basket.move();
    }
}

Thank you for your help

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0

in the method newBasket() and newLauncher() you have 'ControlElement' in front of the variable:

private void newBasket(){ //making a basket
    ControlElement basket = new ControlElement("basket.png", this, getWidth() / 2, getHeight() - 25);
    gameElements.add(basket);
}

That can be deleted since it is a class variable declared at the top, so the program already knows what basket is. Like this:

private void newBasket(){ //making a basket
    basket = new ControlElement("basket.png", this, getWidth() / 2, getHeight() - 25);
    gameElements.add(basket);
}
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