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Thread: Detecting collisions

  1. #1
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    Default Detecting collisions

    I am trying to detect the collision between a moving Jbutton and stationary Jbuttons using Rectangle Intersection. When I run the program I am getting a NullPointerException on line 'msg1.setBounds(new Rectangle(320,50,400,50));'. Any suggestions on how to fix the problem? Thanks!


    import java.awt.*;
    import javax.swing.*;
    import java.awt.event.*;
     
    public class gamePanel01 extends JPanel implements KeyListener
    {
     
        character ch1 = new character("Hero");
     
        //Global Variables
        JButton blocker01;
        JButton blocker02;
        JButton blocker03;
        JButton blocker04;
        JButton blocker05;
        JLabel msg1;
        JLabel msg2;
     
        //Character movement Variables
        int x=100;
        int y=100;
     
        //Image for background of gamePanel01
        ClassLoader cl = this.getClass().getClassLoader();    
        Image gamePanelBG = new ImageIcon(cl.getResource("images/gamePanel01.jpg")).getImage();
        ImageIcon PSUBlocker = new ImageIcon(cl.getResource("images/PSU_Helmet_Blocker.gif"));
        ImageIcon PSULionRight = new ImageIcon(cl.getResource("images/NittanyLion_Mini_Right.png"));
        ImageIcon PSULionLeft = new ImageIcon(cl.getResource("images/NittanyLion_Mini_Left.png"));
     
        public gamePanel01()
        {
        super();
        setLayout(null);
     
        add(ch1);    
        ch1.setIcon(PSULionRight);
        ch1.setBounds(new Rectangle(x,y,45,45));
        ch1.addKeyListener(this);
     
        ch1.setFocusPainted(false);
        ch1.setContentAreaFilled(false);
        ch1.setBorderPainted(false);
     
     
        //Blocker Buttons created/added
        blocker01 = new JButton();
        blocker02 = new JButton();
        blocker03 = new JButton();
        blocker04 = new JButton();
        blocker05 = new JButton();
     
        add(blocker01);
        add(blocker02);
        add(blocker03);
        add(blocker04);
        add(blocker05);
        //Blocker Button Placement-------------------------------------------------
        //**********Rectangle Parameters (x,y,length,height)
        blocker01.setBounds(new Rectangle(250,150,45,45));
        blocker02.setBounds(new Rectangle(250,195,45,45));
        blocker03.setBounds(new Rectangle(400,240,45,45));
        blocker04.setBounds(new Rectangle(400,285,45,45));
        blocker05.setBounds(new Rectangle(400,330,45,45));
     
     
        //Set Images to Buttons and Button Parameters
        blocker01.setIcon(PSUBlocker);
        blocker01.setFocusPainted(false);
        blocker01.setContentAreaFilled(false);
        blocker01.setBorderPainted(false);
     
        blocker02.setIcon(PSUBlocker);
        blocker02.setFocusPainted(false);
        blocker02.setContentAreaFilled(false);
        blocker02.setBorderPainted(false);
     
        blocker03.setIcon(PSUBlocker);
        blocker03.setFocusPainted(false);
        blocker03.setContentAreaFilled(false);
        blocker03.setBorderPainted(false);
     
        blocker04.setIcon(PSUBlocker);
        blocker04.setFocusPainted(false);
        blocker04.setContentAreaFilled(false);
        blocker04.setBorderPainted(false);
     
        blocker05.setIcon(PSUBlocker);
        blocker05.setFocusPainted(false);
        blocker05.setContentAreaFilled(false);
        blocker05.setBorderPainted(false);
     
        msg1.setBounds(new Rectangle(320,50,400,50));
        msg2.setBounds(new Rectangle(320,280,400,50));
        add(msg1);
        add(msg2);
     
         if (ch1.intersects(blocker01))
        {msg1.setText("ch1 and blocker01 intersect");}
        else
        {msg1.setText("ch1 and blocker01 do not intersect");}
        if (ch1.intersects(blocker02))
        {msg2.setText("ch1 and blocker02 intersect");}
        else
        {msg2.setText("ch1 and blocker02 do not intersect");}
     
        }
        @Override
       public void paintComponent(Graphics g)
       {
       super.paintComponent(g);
       g.drawImage(gamePanelBG, 0, 0, this);
        }
     
       public void keyPressed(KeyEvent ev)
      {
          int k= ev.getKeyCode();      
          if (k==KeyEvent.VK_LEFT){
              x=x-5;
              ch1.setIcon(PSULionLeft);
          }
          if(k==KeyEvent.VK_RIGHT) {
              x=x+5;
              ch1.setIcon(PSULionRight);
          }
          if(k==KeyEvent.VK_UP) {y=y-5;}
          if(k==KeyEvent.VK_DOWN) {y=y+5;}
          ch1.setBounds(new Rectangle(x,y,45,45));
          //Rectangle r1=new Rectangle(x,y,45,45);
          //setBounds(r1);
     
      }
       public void keyReleased(KeyEvent evt) {  }
     
       public void keyTyped(KeyEvent evt) {  }
     
    }


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Detecting collisions

    getting a NullPointerException on line 'msg1.setBounds(new Rectangle(320,50,400,50)
    What is the value of the variable: msg1? That looks like the only source of a NPE on that line.
    If you don't understand my answer, don't ignore it, ask a question.

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