Java 用于简单登录的Android文件I/O

我正在编写一个关于使用文件I/O登录的非常简单的示例：

 public void onClickLogin(View v) throws FileNotFoundException
{
    String username = "", password = "";

    TextView nomeUtenteView = (TextView)findViewById(R.id.tUserName);
    username = nomeUtenteView.getText().toString();

    TextView passwordView = (TextView)findViewById(R.id.tPassword);
    password = passwordView.getText().toString();

    if (!findUser(username, password, false))
        Toast.makeText(getApplicationContext(), "Account not exists", Toast.LENGTH_SHORT).show();
    else {
        Intent intent = new Intent(this, HomeActivity.class); 
        Bundle bundle = new Bundle(); 
        bundle.putString("user", username);
        intent.putExtras(bundle);
        startActivity(intent);
    }
}

public void onClickRegister(View v) {

    String username = "", password = "";

    TextView nomeUtenteView = (TextView)findViewById(R.id.tUserName);
    username = nomeUtenteView.getText().toString();

    TextView passwordView = (TextView)findViewById(R.id.tPassword);
    password = passwordView.getText().toString();

    try {
        if (findUser(nomeUtente, password, true))
            Toast.makeText(getApplicationContext(), "Username (" + username + ") already in use!", Toast.LENGTH_LONG).show();
        else
        {
            String nomeFileAccounts = getApplicationContext().getFilesDir().getPath().toString() + "/" + getString(R.string.nomeFileAccounts);

            FileWriter fileScrivi = new FileWriter(nomeFileAccounts, true);
            fileScrivi.append(userName+" " + password + "\n");
            fileScrivi.close();

            Toast.makeText(getApplicationContext(), "New account registered. Wellcome, " + userName + "!", Toast.LENGTH_LONG).show();
        }
    }
    catch (FileNotFoundException e)
    {
        e.printStackTrace();
    }
    catch (IOException e)
    {
        e.printStackTrace();
    }

}

boolean findUser(String userName, String psw, boolean userOnly)
{
    String nomeFileAccounts = getApplicationContext().getFilesDir().getPath() + "/" + getString(R.string.nomeFileAccounts);
    boolean userExists = false;

    File f = new File(nomeFileAccounts);

    if (f.exists()) {

        try {
            FileReader fileLeggi = new FileReader(nomeFileAccounts);
            BufferedReader lettore = new BufferedReader(fileLeggi);


            String rigaLetta = "";
            String[] datiAccount = null;

            while ((rigaLetta=lettore.readLine()) != null && !userExists)
            {
                datiAccount = rigaLetta.split(" ");

                userExists = datiAccount[0].compareTo(userName) == 0;

                if (!soloUser)
                    userExists  = userExists  && datiAccount[1].compareTo(psw)==0;
            }
            lettore.close();
            fileLeggi.close();

        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

    else
        try {
            f.createNewFile();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.PrintStack();
        }
    return userExists ;
}

这在Android Emulator上运行，通过Eclipse的文件浏览器，我可以在data/data/application/中看到用户的文件

---

但当我导出签名的apk并试用我的Galaxy Note 3时，我尝试单击register并运行，但登录的click让应用程序崩溃。。怎么了？

请粘贴崩溃日志。如何在真实设备上生成崩溃日志？通过USB或WiFi将设备连接到计算机，然后从eclipse在设备上运行应用程序。