请问在j2me中多个画面怎样切换啊

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请问在j2me中多个画面怎样切换啊5

刚学j2me，仿照示例做了两个Form,并添加了相应的command,运行后，点击Form1中的按钮，进入到了Form2，再按Form2中的按钮，我想退出或是退回Form1，但界面就不变化了，调试时按Form1中的按钮会暂停下来，但按Form2中的按钮就没反应了。下面是代码，请大家帮我看一下，谢谢！

public class Login extends MIDlet implements CommandListener {

	TextField UserName = null;
	TextField Password = null;
	Form authForm, mainscreen;
	TextBox t = null;
	StringBuffer b = new StringBuffer("hello\n");
	private Display myDisplay = null;
	private Command okCommand = new Command("OK", Command.OK, 1);
	private Command exitCommand = new Command("Exit", Command.EXIT, 2);
	private Command backCommand = new Command("Back", Command.BACK, 2);
	private Alert alert = null;

	public Login() {
		myDisplay = Display.getDisplay(this);

		UserName = new TextField("Your Name", "gleosoft", 16, TextField.ANY);
		Password = new TextField("Password", "gleotechadmin", 16, TextField.ANY);
		authForm = new Form("Identification");
		mainscreen = new Form("Logging IN");
		mainscreen.append("Logging in....");
		mainscreen.addCommand(backCommand);
		authForm.append(UserName);
		authForm.append(Password);
		authForm.addCommand(okCommand);
		authForm.addCommand(exitCommand);
	}

	public void startApp() throws MIDletStateChangeException {
		authForm.setCommandListener(this);
		myDisplay.setCurrent(authForm);
	}

	public void pauseApp() {
	}

	protected void destroyApp(boolean unconditional) throws MIDletStateChangeException {
	}

	public void commandAction(Command c, Displayable d) {

		if ((c == okCommand) && (d == authForm)) {
			if (UserName.getString().equals("") || Password.getString().equals("")) {
				alert = new Alert("Error", "You should enter Username and Password", null,
						AlertType.ERROR);
				alert.setTimeout(Alert.FOREVER);
				myDisplay.setCurrent(alert);
			} else {
				// myDisplay.setCurrent(mainscreen);
				login(UserName.getString(), Password.getString());
			}
		}
		if ((c == backCommand) && (d == mainscreen)) {
			myDisplay.setCurrent(authForm);
		}
		if ((c == exitCommand) && (d == authForm)) {
			notifyDestroyed();
		}
	}

	public void login(String UserName, String Password) {
		HttpConnection connection = null;
		DataInputStream in = null;
		String url = "http://localhost/j2me.htm";
		OutputStream out = null;
		try {
// 省略了一些代码
			mainscreen.append(b.toString());
			if (in != null)
				in.close();
			if (out != null)
				out.close();
			if (connection != null)
				connection.close();
		} catch (IOException x) {
		}
		myDisplay.setCurrent(mainscreen);
	}
}

问题补充：

gundumw100 写道

url = "http://localhost/j2me.htm";
这里是不是再联网啊，需要再开一条线程的！

你好，原本代码是要访问网络的，可以正常访问的，但就是不能再进入别的界面了，所以我就把访问网络的代码取消了，但问题还是老样子，不知道怎么弄了。

J2ME