public class myj2me extends MIDlet {
         Display display.....//初始化过程略去
         //构造函数中
    canvas1 can1 = new canvas1(this);
    canvas2 can1 = new canvas2(this);
         public void startApp(){display.setCurrent(can1);}
         public void setcanvas1(){display.setCurrent(can1);}
         public void setcanvas2(){display.setCurrent(can2);}
}
class canvas1 extends Canvas implements CommandListener {
    myj2me j2me;
    public canvas1(myj2me my_j2me) {
        j2me = my_j2me;
    }
    public void commandAction(Command cmd,Displayable dis){
            if(cmd==...){
                     j2me.setcanvas2();
            }
        }
}
class canvas2 extends Canvas implements CommandListener {
    myj2me j2me;

    public canvas2(myj2me my_j2me) {
        j2me = my_j2me;
    }
    public void commandAction(Command cmd,Displayable dis){
            if(cmd==...){
                     j2me.setcanvas3();
            }
        }
}