java me - j2me sprite not working -

first, i'm sorry bad english. i'm newbie j2me

i wrote below code after watched tutorial not working. don't know happen it.

animationcanvas.java

package example;  import java.io.ioexception; import javax.microedition.lcdui.*; import javax.microedition.lcdui.game.gamecanvas; import javax.microedition.lcdui.game.layermanager; import javax.microedition.lcdui.game.sprite;  public class animationcanvas extends gamecanvas implements runnable {      private sprite ca;     private int framewidth = 14;     private int frameheight = 14;     private boolean playing = true;     private int a=1;      public animationcanvas(){         super(true);         try {             ca = new sprite(image.createimage("ca.png"), framewidth, frameheight);         } catch (ioexception ex) {             ex.printstacktrace();         }     }      public void start() {         thread runner = new thread(this);         runner.start();     }      public void run(){         while (playing){             drawdisplay(getgraphics());             try{                 thread.sleep(10);             } catch(exception e){}         }     }      public void drawdisplay(graphics g){         g.setcolor(0x000000);         g.fillrect(0,0,getwidth(),getheight());         ca.setframe(1);         ca.paint(g);         flushgraphics();     }      public void stop(){         playing=false;     } } 

and animationmidlet.java

 package example;   import java.io.ioexception;  import javax.microedition.midlet.*;  import javax.microedition.lcdui.*;   public class animationmidlet extends midlet {       private display display;       private animationcanvas canvas;        public animationmidlet() throws ioexception {            display = display.getdisplay(this);            canvas = new animationcanvas();       }        private void initialize() {                                                     // write pre-initialize user code here             // write post-initialize user code here       }                                    public void startmidlet() {                                                  // write pre-action user code here             // write post-action user code here       }                                       public void resumemidlet() {                                                   // write pre-action user code here             // write post-action user code here       }                                      public void switchdisplayable(alert alert, displayable nextdisplayable) {                                                        // write pre-switch user code here            display display = getdisplay();                                                           if (alert == null) {                 display.setcurrent(nextdisplayable);            } else {                 display.setcurrent(alert, nextdisplayable);            }                                                         // write post-switch user code here       }                                            public display getdisplay() {            return display.getdisplay(this);       }       public void startapp() {            if(canvas!=null){                 display.setcurrent(canvas);                 canvas.start();            }       }        public void pauseapp() {       }        public void destroyapp(boolean unconditional) {            canvas.stop();       }   } 

and output

running in identified_third_party security domain java.io.ioexception uncaught exception java/lang/nullpointerexception. @ javax.microedition.lcdui.immutableimage.getimagefromstream(image.java:968) @ javax.microedition.lcdui.immutableimage.(image.java:939) @ javax.microedition.lcdui.image.createimage(image.java:313) @ example.animationcanvas.(animationcanvas.java:25) @ example.animationmidlet.(animationmidlet.java:25) @ java.lang.class.runcustomcode(+0) @ com.sun.midp.midlet.midletstate.createmidlet(+34)

thanks reading!