Android Studio：登录后应用停止工作

Question

所以我是Android Studio的新手，还在学习。我正在尝试创建一个允许用户与他的Facebook连接的应用程序，一旦他登录，他就可以转到个人资料页面。以下示例中的facebook UserID会在成功时传递给类配置文件。然而，在用facebook登录后，我的应用程序崩溃了..我做错了什么？

public class MainActivity extends AppCompatActivity {
    LoginButton loginButton;
    TextView textView;
    String s;
    CallbackManager callbackManager;
    Realm realm;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        FacebookSdk.sdkInitialize(getApplicationContext());
        setContentView(R.layout.activity_main);
        loginButton = (LoginButton) findViewById(R.id.login_button);
        textView = (TextView) findViewById(R.id.Textview);
        callbackManager = CallbackManager.Factory.create();
        loginButton.registerCallback(callbackManager, new FacebookCallback<LoginResult>() {
            @Override
            public void onSuccess(LoginResult loginResult) {
                //textView.setText("Login success "+loginResult.getAccessToken().getUserId() +"\n"+loginResult.getAccessToken().getToken());
                    s = loginResult.getAccessToken().getUserId();

                        Intent i= new Intent(MainActivity.this,profiles.class);
                        i.putExtra("Id",s);
                        startActivity(i);
            }

            @Override
            public void onCancel() {
                textView.setText("Login Failed");
            }

            @Override
            public void onError(FacebookException error) {

            }
        });
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        callbackManager.onActivityResult(requestCode,resultCode,data);
    }
}

配置文件部分基本上由3个edittexts组成，允许用户输入他的信息并将其存储在领域数据库中

public class profiles extends AppCompatActivity {
EditText username,age,country;
Realm realm;
      @Override
        protected void onCreate(@Nullable Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.profile);
            Bundle bundle= getIntent().getExtras();
            final String userid;
            userid = bundle.getString("Id");
            username= (EditText) findViewById(R.id.username);
            age= (EditText) findViewById(R.id.age);
            country= (EditText) findViewById(R.id.country);

            Realm.init(this);
            realm = Realm.getDefaultInstance();
            findViewById(R.id.Continue).setOnClickListener(new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    realm.beginTransaction();
                        Users obj= realm.createObject(Users.class);
                        obj.setUsername(username.getText().toString());
                        obj.setCountry(country.getText().toString());
                        obj.setAge(age.getText().toString());
                        obj.setUserId(userid);
                    realm.commitTransaction();
                }
            });
        }
    }

这里是使用的getter和setter的用户类，

public class Users extends RealmObject {
    public void setUserId(String userId) {
        UserId= userId;
    }

    public void setUsername(String username) {
        Username = username;
    }

    public void setCountry(String country) {
        Country = country;
    }



    String UserId;
    String Username;
    String Country;

    public String getAge() {
        return age;
    }

    public void setAge(String age) {
        this.age = age;
    }

    String age;

    public String getUsername() {
        return Username;
    }

    public String getCountry() {
        return Country;
    }



    public String getUserId() {
        return UserId;
    }
}