JFrame application HELP Needed ! ! ! (STILL NEED HELP)

[Douglas Braxton]

Ranch Hands:

There is a lot of code here. Do not let it throw you. Most of it is here to avoid having to repost it if someone has a question
The problem lies within the statement followed by this comment (I think)
// # # # PROBLEM # # # in class MYFrame.
All code compiles clean.
OBJECT: Illustrate inheritance exercise which will have 15 random shapes drawn on a JFrame.
PROBLEM: When I execute the Driver the JFrame is BLANK. If you drag the frame the program executes as expected but it produces the following list of runtime errors:
java.lang.NullPointerException
at MyFrame.paint(MyFrame.java:55)
at sun.awt.RepaintArea.paint(RepaintArea.java:177)
at sun.awt.windows.WComponentPeer.handleEvent(WComponentPeer.java:260)
at java.awt.Component.dispatchEventImpl(Component.java:3699)
at java.awt.Container.dispatchEventImpl(Container.java:1623)
at java.awt.Window.dispatchEventImpl(Window.java:1590)
at java.awt.Component.dispatchEvent(Component.java:3480)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:450)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:197)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:150)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:144)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:136)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:99)
Thanks for your expert help.
75gator

/*
 * Filename MyShapesDriver.java
 */
import javax.swing.JFrame;
public class MyShapesDriver
{
public static void main (String[ ] arg)
    {
         MyFrame mFrame = new MyFrame();
        mFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
         //System.exit(0);
    }// terminate main
}// end of MyShapesDriver
// NEW CLASS FILE (MyFrame) STARTS HERE
/*
 * Filename MyFrame.java
 */
import java.awt.*;
import java.text.*;
import javax.swing.JFrame;
public class MyFrame extends JFrame
{
    
    MyShapes [  ] drawShapes = new MyShapes [ 15 ]; 
    
    public MyFrame() 
    {
         setSize( 1000, 1000 );
         setVisible(true);
                    
         for ( int i = 0; i < 15; i++ ) 
         {
                int x1 = 1 + (int) (Math.random() * 300);
                int y1 = 1 + (int) (Math.random() * 300);
                int x2 = 1 + (int) (Math.random() * 300);
                int y2 = 1 + (int) (Math.random() * 300);
                int pickShape = (int) (Math.random() * 3);
                switch ( pickShape )
                {
                case 0:
                    drawShapes[ i ] = new MyLine (x1, y1, x2, y2); 
                    break;
                case 1:
                    drawShapes[ i ] = new MyOval (x1, y1, x2, y2); 
                    break;
                case 2:
                    drawShapes[ i ] = new MyRect (x1, y1, x2, y2); 
                    break;
                }
         }
    }    
    public void paint(Graphics g)
    {
        super.paint(g);
        for ( int i = 0; i < drawShapes.length; i++ ) 
        {
            drawShapes[ i ].draw(g);// # # # PROBLEM # # # 
        }
    }
}    
// NEW CLASS FILE (MyShapes) STARTS HERE
 import java.awt.Graphics;           // import class Graphics
   import java.awt.Font;
   import java.text.*;
   import java.io.*;
public abstract class MyShapes 
{
    private int x1, y1, x2, y2;
// constructor assigns value zero (0) to the variables x1, y1, x2, y2     
    MyShapes() 
    {
        x1 = 0; 
        y1 = 0; 
        x2 = 0;
        y2 = 0;
    }
    // constructor assigns input parameters to the defined integer names
    MyShapes(int ix1, int iy1, int ix2, int iy2) 
    {
        x1 = ix1; 
        y1 = iy1; 
        x2 = ix2;
        y2 = iy2;
    }
    void setX1(int ix1)
    {
        x1 = ix1;
    }
    void setY1(int iy1)
    {
        y1 = iy1;
    }
    void setX2(int ix2)
    {
        x2 = ix2;
    }
    void setY2(int iy2)
    {
        y2 = iy2;
    }
    int getX1()
    {
        return x1;
    }
    int getY1()
    {
        return y1;
    }
    int getX2()
    {
        return x2;
    }
    int getY2()
    {
        return y2;
    }
    public abstract void draw(Graphics g) ;
} // end of class
// NEW CLASS FILE (MyLine) STARTS HERE
 import java.awt.Graphics;           // import class Graphics
  
public class MyLine extends MyShapes
{
// constructor assigns value zero (0) to the variables x1, y1, x2, y2     
    MyLine() 
    {
        super();
    }
    // constructor assigns input parameters to the defined integer names
    MyLine(int ix1, int iy1, int ix2, int iy2) 
    {
        super(ix1,iy1,ix2,iy2); 
    }
   public void draw(Graphics g) 
   {
       g.drawLine(this.getX1(), this.getY1(), this.getX2(), this.getY2());
   }
}   
// NEW CLASS FILE (MyRect) STARTS HERE
import java.awt.Graphics;           // import class Graphics
  
class MyRect extends MyShapes
{
// constructor assigns value zero (0) to the variables x1, y1, x2, y2     
    MyRect() 
    {
        super();
    }
    // constructor assigns input parameters to the defined integer names
    MyRect(int ix1, int iy1, int ix2, int iy2) 
    {
         super(ix1,iy1,ix2,iy2); 
    }
    public void draw(Graphics g) 
    {
        g.drawRect(this.getX1(), this.getY1(), this.getX2(), this.getY2());
    }   
}
// NEW CLASS FILE (MyOval) STARTS HERE
import java.awt.Graphics;           // import class Graphics
   
class MyOval extends MyShapes
{
// constructor assigns value zero (0) to the variables x1, y1, x2, y2     
    MyOval() 
    {
        super();
    }
    // constructor assigns input parameters to the defined integer names
    MyOval(int ix1, int iy1, int ix2, int iy2) 
    {
        super(ix1,iy1,ix2,iy2); 
    }
    public void draw(Graphics g) 
    {
       g.drawOval(this.getX1(), this.getY1(), this.getX2(), this.getY2());
    }   
}

[ April 13, 2004: Message edited by: Douglas Braxton ]

[Dirk Schreckmann]

Moving this to the Swing / JFC / AWT forum, where they love to get all messy with this GUI stuff...

[Polina Bee]

Hi Douglas.
Just make setVisible(true) the last opeation in MyFrame constructor or remove it from constructor at all and put to the main function like this:
public static void main (String[ ] arg)
{
MyFrame mFrame = new MyFrame();
mFrame.setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
mFrame.setVisible(true);
//System.exit(0);
}// terminate main
}// end of MyShapesDriver
Like it id now, your program tries to draw shapes before you create them and you're getting the NullPointerException.
Good luck.
Polina

[Douglas Braxton]

Thanks for the help. Problem solved!