Nothing come out from Canvas, pls help!

Question

No error but nothing come out. Please help!
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class StGeorgeFlag extends Applet implements ActionListener{ //, MouseListener, MouseMotionListener{
     Panel p;
     MyCanvas mycanvas;
     PlayButton play;
     ConfirmButton confirm;     
     SolutionButton solution;
     Dimension d;
     Graphics g;
     public void init(){
          int width = getSize().width;
          int height= getSize().height;
          p = new Panel();               
          setBackground(Color.lightGray);
          MyCanvas mycanvas = new MyCanvas();  // create the canvas          
          mycanvas.setSize(width-4, height-4);
          play = new PlayButton(this);
          confirm = new ConfirmButton(this);
          solution = new SolutionButton(this);
          add(play);
          add(confirm);
          add(solution);
          p.setLayout(new GridLayout(1,4,3,3));
          p.add(play);
          p.add(confirm);
          p.add(solution);
          setLayout(new BorderLayout(3,3));       // button border
          add("Center",mycanvas);             // add canvas and controls to the applet
          add("South",p);
     public void actionPerformed(ActionEvent e){
         if (e.getSource() == play) mycanvas.rectangle();                       
              else if (e.getSource() == confirm) mycanvas.rectangle();
               else if (e.getSource() == solution) mycanvas.solution();
     public void mousePressed(MouseEvent me){}
     public void mouseDragged(MouseEvent evt) {}
     public void mouseReleased(MouseEvent me){}
     public void mouseClicked(MouseEvent me){}  
     public void mouseEntered(MouseEvent me){}       
     public void mouseExited(MouseEvent me) {}
}  // end Class StGeorgFlag
class MyCanvas extends Canvas {
     Dimension d;
     public void paint (Graphics g){
           rectangle();
     public void rectangle() {
          Graphics g = getGraphics();
          Dimension d = getSize();
          int width = d.width;
          int height = d.height;
          g.setColor(Color.red);
          g.fillRect(2,2,width-4,height-4);
          int y = 2;          // width
          for (int row=0; row<2; row++){                         
               int x = 2;     // height               
               for (int col=0; col<2; col++){     
                    g.setColor(Color.white);
                    g.fillRect(x,y, width/5, height/5);                              
                    x = (x + width-(width/5+4));               
               y = y+height-(height/5+4);                                        
     } // end method rectangle
     public void solution() {
               Graphics g = getGraphics();
               int width = d.width;
               int height = d.height;
               g.setColor(Color.red);
               g.fillRect(2,2,width-4,height-4);
               int y = 2;          // width
               for (int row=0; row<2; row++){                         
                    int x = 2;     // height               
                    for (int col=0; col<2; col++){     
                         g.setColor(Color.white);
                         g.fillRect(x,y, width/8*3, height/3);                              
                         x = (x + (width/8*5)+4);               
                    y = y+(height/3*2+4);                                        
               g.setColor(Color.black);
               g.drawString("Solution" , width/5,height/3);
               g.drawString("========"      , width/5,height/3+20);
               g.drawString("- find the length diagonal (from corner to corner)" , width/5,(height/3)+40);
               g.drawString("- divide diagonal by 2 to find the mid point" , width/5,(height/3)+60);
               g.drawString("- find a quarter of the area of the flag " , width/5,(height/3)+80);
               g.drawString("- So, the white are is: [(3m/8*2)*(2m/3)]*4 = 6 (half of flag area)", width/5,(height/3)+100);
     }// end method solution
} // end class MyCanvas
class PlayButton extends Button {
     PlayButton(StGeorgeFlag sgf) {
          super("Play/Reset");
          addActionListener(sgf);
} // end Class PlayButton
class ConfirmButton extends Button {     
     ConfirmButton(StGeorgeFlag sgf) { 
          super("Confirm");
          addActionListener(sgf);
} // end class ResetButton
class SolutionButton extends Button {
     SolutionButton(StGeorgeFlag sgf) { 
          super("Solution");
          addActionListener(sgf);
} // end class SolutionButton

Answer 1

NewJava wrote:
No error Not sure that I agree with this. I get an NPE when I try to run this.
but nothing come out. Please help!You're declaring your MyCanvas object twice, once in the class, and once in the init method, and only construct the second of the two. Declare this object only once -- in the class, and construct this same object once, and you're program will be closer to completion:
Change this:
    MyCanvas mycanvas;
    public void init()
        int width = getSize().width;
        int height = getSize().height;
        p = new Panel();
        setBackground(Color.lightGray);
        MyCanvas mycanvas = new MyCanvas(); // create the canvas to this:
    MyCanvas mycanvas;
    public void init()
        int width = getSize().width;
        int height = getSize().height;
        p = new Panel();
        setBackground(Color.lightGray);
        //MyCanvas mycanvas = new MyCanvas(); // create the canvas
        mycanvas = new MyCanvas(); // create the canvas