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Thread: TimerFun

  1. #1
    Junior Member KTJW88's Avatar
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    Default TimerFun

    Error Message when I run a program

    Exception in thread "main" java.lang.NullPointerException
    	at TimerFun.GUIMaker(TimerFun.java:86)
    	at TimerFun.<init>(TimerFun.java:226)
    	at TimerFun.main(TimerFun.java:231)

    MY java code

    import java.awt.*; 
    import java.awt.event.*;  
    import javax.swing.*; 
    import java.io.*;
    import javax.swing.Timer.*; 
    import java.util.*; 
    import java.text.SimpleDateFormat; 
     
    public class TimerFun extends Thread implements ActionListener 
    {
       //Data Types (Attibrutes)
       private JPanel jp1, jp2, jp3, jp4, jp5,
                      jp6, jp7, jp8, rainbowColor,
                      pbjp;
       private JLabel jlDate; 
       private JFrame gui = new JFrame("Kevin T. Whetstone's FUN with Timers & Threads");
       private JProgressBar jpb = new JProgressBar();  
     
       //GUI maker to make coding easier
       public void GUIMaker()
       {
          //JFrame objects
          gui.setLayout(new BorderLayout());
          gui.setSize(350,350);
          gui.setLocationRelativeTo(null);
          gui.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          gui.setVisible(true);
     
          //JMenuBar objects
          JMenuBar jmb = new JMenuBar(); 
          JMenu jmFile = new JMenu("File");
          JMenu jmHelp = new JMenu("Help");
          JMenuItem jmiExit = new JMenuItem("Exit");
          JMenuItem jmiAbout = new JMenuItem("About");
     
          //adding JMenuBar objects to the JFrame, gui
          jmFile.add(jmiExit); 
          jmHelp.add(jmiAbout); 
          jmb.add(jmFile); 
          jmb.add(jmHelp); 
          gui.setJMenuBar(jmb);
     
          //Mnemonic objects
          jmFile.setMnemonic(KeyEvent.VK_F);
          jmHelp.setMnemonic(KeyEvent.VK_H);
          jmiExit.setMnemonic(KeyEvent.VK_X);
          jmiAbout.setMnemonic(KeyEvent.VK_A);
     
          //Adding ActionListener
          jmiExit.addActionListener(this); 
          jmiAbout.addActionListener(this);
     
          //Date & Time
          jlDate = new JLabel();
          Time t1 = new Time(jlDate);
          java.util.Timer t2 = new java.util.Timer();
          t2.scheduleAtFixedRate(new Time(jlDate), 10, 10);
          gui.add(jlDate, BorderLayout.NORTH);
     
          //Adding Progress Bars 
          pbjp = new JPanel();
          jpb = new JProgressBar();
    	   pbjp.add(new JLabel("Progress Bar: "));
    		progressBar pbInner = new progressBar();
    		pbjp.add(jpb);
    		jpb.setOrientation(JProgressBar.HORIZONTAL);	
    		jpb.setMinimum(0);										
    		jpb.setMaximum(100);									
    		jpb.setValue(0);										
    		jpb.setStringPainted( true );		
          jpb.setIndeterminate(false);				
    		gui.add(pbjp, BorderLayout.SOUTH);
          jpb.setString("Three seconds  before starting" );
          try
          { 
             Thread.sleep(3000); 
          }
    		catch(InterruptedException ie)
          { 	
             ie.printStackTrace();	
          }
    		   pbInner.start();
     
          //Rainbow Color & Timer Color    
          rainbowColor = new JPanel(new GridLayout(7,0));
          jp1.setBackground(Color.red); 
          rainbowColor.add(jp1); 
          jp2.setBackground(Color.orange); 
          rainbowColor.add(jp2);
          jp3.setBackground(Color.yellow); 
          rainbowColor.add(jp3);
          jp4.setBackground(Color.green); 
          rainbowColor.add(jp4);
          jp5.setBackground(Color.blue); 
          rainbowColor.add(jp5);
          jp6.setBackground(new Color(70,0,130)); 
          rainbowColor.add(jp6);
          jp7.setBackground(new Color(238,130,238)); 
          rainbowColor.add(jp7);
          gui.add(rainbowColor, BorderLayout.CENTER); 
          java.util.Timer c = new java.util.Timer(); 
          c.scheduleAtFixedRate(new ColorBar(jp1,jp2,jp3,jp4,jp5,jp6,jp7,jp8), 2000, 500); 
     
       }
     
       //Progress Bar with Thread
       protected class progressBar extends Thread 
       {
    		public void run() 
          {
    			jpb.setString(null);
    			jpb.setStringPainted(true);
    			jpb.setIndeterminate(false);
     
             int count = 0;
     
             for(count =0; count<=100; count++)
             {
    				jpb.setValue(count);
     
                try
                { 
                   Thread.sleep(50); 
                }
    				catch(InterruptedException ie) 
                {
    					ie.printStackTrace();
    				}
    			}
     
    			jpb.setStringPainted(true);
    			jpb.setString("Cylons Scanning");
     
    			try
             { 	
                Thread.sleep(3000); 
             }
    			catch(InterruptedException ie)
             {
    				ie.printStackTrace();
    			}
     			   jpb.setIndeterminate(true); 
     
    		}
     
    	}
     
       //ColorBars for background color with timer
       class ColorBar extends TimerTask
       {
          JPanel jp1, jp2, jp3, jp4,
                 jp5, jp6, jp7, jp8; 
     
          public ColorBar(JPanel jp1, JPanel jp2, JPanel jp3, JPanel jp4, JPanel jp5, JPanel jp6, JPanel jp7, JPanel jp8)
          {
             this.jp1 = jp1;
             this.jp2 = jp2;
             this.jp3 = jp3;
             this.jp4 = jp4;
             this.jp5 = jp5;
             this.jp6 = jp6;
             this.jp7 = jp7;
             this.jp8 = jp8;     
          } 
          public void run()
          {
             jp8.setBackground(jp1.getBackground());   
             jp1.setBackground(jp2.getBackground());
             jp2.setBackground(jp3.getBackground());  
             jp3.setBackground(jp4.getBackground());
             jp4.setBackground(jp5.getBackground());
             jp5.setBackground(jp6.getBackground());
             jp6.setBackground(jp7.getBackground());
             jp7.setBackground(jp8.getBackground()); 
          }     
       }
     
       //Time with Date, time (hour, min, second)
       class Time extends TimerTask
       {
          JLabel jlDate;
          SimpleDateFormat sdf = new SimpleDateFormat("EEE, d MMM yyyy HH:mm:ss");
     
          public Time(JLabel jlDate)
          {
             this.jlDate = jlDate;
          }
     
          public void run()
          {
             Calendar curCal = Calendar.getInstance();
             Date curTime = curCal.getTime();
             jlDate.setText(sdf.format(curTime));
             jlDate.setFont(new Font("Arial", Font.BOLD, 20)); 
             jlDate.setForeground(Color.red);
             jlDate.setHorizontalAlignment(0);   
          } 
       }
     
       public void actionPerformed(ActionEvent e)
       {
          Object select = e.getActionCommand();
     
     
          if(select == "Exit")
          {
             try
             {
                Thread.sleep(2000); 
                System.exit(0);
             }
             catch(InterruptedException ie)
             {
                ie.printStackTrace();
      			}
          }
          else if(select == "About")
          {
             String stringFormat = String.format("Fun with Timers and Threads\nby: Kevin T. Whetstone\nFebruary 19, 2014");
             JOptionPane.showMessageDialog(null, stringFormat); 
          }
       }
     
       public TimerFun()
       {
          GUIMaker();
       }
     
       public static void main(String[] args)
       {
          new TimerFun();
       }
     
    }

  2. #2
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    Default Re: TimerFun

    Welcome! Thank you for taking the time to learn to post code correctly. If you haven't already, please read this topic to learn other useful info for new members.

    The JPanels, jp1, jp2, etc., are never initialized, so that when jp1 is first used on line 86 (look at that line as indicated by the error message/stack trace) it is null.

    You often hear the phrase "Swing is not thread safe." That means that using a Threads with Swing is not a good idea, and sleeping a thread in a Swing app is an excellent way to demonstrate why "Swing is not thread safe.".

  3. #3
    Junior Member KTJW88's Avatar
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    Default Re: TimerFun

    Awesome, and didn't know about it. It is working like a charm now.

    Thank you for your help,

    Kevin

  4. #4
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    Default Re: TimerFun

    Glad you solved the problem.

    I believe the following:

    "Warning: Swing is not thread safe. For more information see Swing's Threading Policy."

    is on every javax.swing API page. You don't have to memorize the API of every Java SE class you use, but you should give each one a look, and when you see something interesting (like maybe that warning), you should dig a bit deeper.

  5. The Following User Says Thank You to GregBrannon For This Useful Post:

    KTJW88 (March 1st, 2014)