public class code extends MIDlet implements CommandListener
{

    Display dis;
    Form f;
    TextField t1,t2,t3,t4,t5,t6,t7;
    Command c1,c2,c3,c4,c5,c6;
    TextBox b1,b2,b3,b4;
    Image i1,i2;
    ImageItem m1,m2;
    String str="",s1="",s2="";
    public code()
    {
        // TODO 自动生成构造函数存根
    }

    protected void destroyApp(boolean arg0) throws MIDletStateChangeException
    {
        // TODO 自动生成方法存根

    }

    protected void pauseApp()
    {
        // TODO 自动生成方法存根

    }

    protected void startApp() throws MIDletStateChangeException
    {
        // TODO 自动生成方法存根
        dis=Display.getDisplay(this);
        f=new Form("登录");
        t1=new TextField("用户",s1,15,0);
        t2=new TextField("密码",s2,15,TextField.PASSWORD);
        c1=new Command("确定",Command.OK,1);
        c2=new Command("返回",Command.BACK,1);
        c3=new Command("继续",Command.OK,1);
        
        try
        {
            i1=Image.createImage("/3.png");
        } catch (IOException e)
        {
            // TODO 自动生成 catch 块
            e.printStackTrace();
        }
        m1=new ImageItem("picture",i1,ImageItem.LAYOUT_CENTER,"error!");
        f.append(m1);
        f.append(t1);
        f.append(t2);
        f.addCommand(c1);
        dis.setCurrent(f);
        f.setCommandListener(this);
        

    }

    public void commandAction(Command c, Displayable arg1)
    {
        // TODO 自动生成方法存根
        if(c==c1)
        {
            if(s1==" "&&s2==" ")
            {
                str="用户名或密码不能为空";
            }
            else
            {
                s1=t1.getString();
                s2=t2.getString();
                str="用户名为"+s1+"   "+"密码为"+s2+"  ";
            }
            b1=new TextBox("用户名为  ",str,15,1);
            b1.addCommand(c2);
            b1.addCommand(c3);
            dis.setCurrent(b1);
            
        }
        if(c==c2)
        {
            dis.setCurrent(f);
        }
        

    }

}

帮你顶一下 等高手帮忙解决

谢谢

我帮你改好了 有事加我QQ109665185
有些变量用不到不要先设好，这样很烦的，也占空间，用到在去设，明白吗，还有你了解的知识不够啊 多看书多操作
package code;
import

import javax.microedition.midlet.*;

import javax.microedition.lcdui.*;
public class code extends MIDlet implements CommandListener
{

    Display display;
    Form f;
    TextField t1,t2;
    Command exitCommand,enterCommand,backCommand,okCommand;
    TextBox b1;
    Image i1;
    ImageItem m1,m2;
    String str="",s1="",s2="";
    public code(){
    }

    protected void destroyApp(boolean arg0) {
    }

    protected void pauseApp(){
    }

    protected void startApp() throws MIDletStateChangeException
    {
        display=Display.getDisplay(this);
        f=new Form("登录");
        t1=new TextField("用户",s1,15,0);
        t2=new TextField("密码",s2,15,TextField.PASSWORD);
        exitCommand=new Command("退出",Command.EXIT,1);
        enterCommand=new Command("确定",Command.SCREEN,1);
        backCommand=new Command("返回",Command.BACK,1);
        okCommand=new Command("继续",Command.OK,1);
        
        try
        {
            i1=Image.createImage("/3.png");
        } catch (IOException e){}
        
        m1=new ImageItem("picture",i1,ImageItem.LAYOUT_CENTER,"error!");
        f.append(m1);
        f.append(t1);
        f.append(t2);
        f.addCommand(exitCommand);
      
        f.addCommand(enterCommand);
        display.setCurrent(f);
        f.setCommandListener(this);
    }

    public void commandAction(Command c, Displayable arg1)
    {
        if(c==exitCommand){
            destroyApp(false);
            notifyDestroyed();
        }
        if(c==enterCommand)
        {
            if(s1==" "&&s2==" ")
            {
                str="用户名或密码不能为空";
            }
            else
            {
                s1=t1.getString();
                s2=t2.getString();
                str="用户名为"+s1+"   "+"密码为"+s2+"  ";
            }
            b1=new TextBox("用户名为  ",str,15,1);
            b1.addCommand(backCommand);
            b1.addCommand(okCommand);
            b1.setCommandListener(this); //注意增加监视器 不然没用   设定按钮 3步骤:1.设定按钮2.增加按钮3.为按钮增加监视器
            display.setCurrent(b1);
            
        }
        else if(c==backCommand){
            display.setCurrent(f);
        }
        else if(c==okCommand)
        {
            display.setCurrent(f);
        }

    }

}