我能够获取所有这些内容，如下面的代码所示，但无法从用户个人资料中检索电子邮件。

我能为此做什么？

我们将不胜感激任何形式的帮助。

早些时候我使用这个来源来获取 Facebook 用户的详细信息并且正在毫无困难地获取数据(包括电子邮件):

public class MainActivity extends Activity {
    private Session.StatusCallback sessionStatusCallback;
    private Session currentSession;

    private Button login;
    private Button logout;
    private Button publishButton;

    private TextView textView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        textView = (TextView) findViewById(R.id.textView);

        // create instace for sessionStatusCallback
        sessionStatusCallback = new Session.StatusCallback() {

            @Override
            public void call(Session session, SessionState state,
                             Exception exception) {
                onSessionStateChange(session, state, exception);

            }
        };

        login = (Button) findViewById(R.id.loginButton);
        login.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                connectToFB();                
            }
        });

        logout = (Button) findViewById(R.id.logoutButton);
        logout.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                if (currentSession != null) {
                    currentSession.closeAndClearTokenInformation();
                    ...
                }
            }
        });

        // publish button
        publishButton = (Button) findViewById(R.id.publishButton);
        publishButton.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                publishStory();

            }
        });

    }

    public void connectToFB() {

        List<String> permissions = new ArrayList<String>();
        permissions.add("publish_actions");

        currentSession = new Session.Builder(this).build();
        currentSession.addCallback(sessionStatusCallback);

        Session.OpenRequest openRequest = new Session.OpenRequest(
                MainActivity.this);
        openRequest.setLoginBehavior(SessionLoginBehavior.SUPPRESS_SSO);
        openRequest.setRequestCode(Session.DEFAULT_AUTHORIZE_ACTIVITY_CODE);
        openRequest.setPermissions(permissions);
        currentSession.openForPublish(openRequest);

    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (currentSession != null) {
            currentSession
                    .onActivityResult(this, requestCode, resultCode, data);
        }
    }

    private void onSessionStateChange(Session session, SessionState state,
                                      Exception exception) {
        if (session != currentSession) {
            return;
        }

        if (state.isOpened()) {
            // Log in just happened.
            Toast.makeText(getApplicationContext(), "session opened",
                    Toast.LENGTH_SHORT).show();

            Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {
                @Override
                public void onCompleted(GraphUser user, Response response) {
                    String fbId = user.getId();
                    String fbName = user.getName();
                    String gender = user.asMap().get("gender").toString();
                    String email = user.asMap().get("email").toString();
                    String first = user.asMap().get("first_name").toString();
                    String last = user.asMap().get("last_name").toString();

                    textView.setText("Id: " + fbId + ", Name: " + fbName + ", Gender: " + gender + ", EmailID: " + email + ", First: " + first + ", Last: " + last);
                }
            });

        } else if (state.isClosed()) {
            // Log out just happened. Update the UI.
            Toast.makeText(getApplicationContext(), "session closed",
                    Toast.LENGTH_SHORT).show();
        }
    }

    public void publishStory() {
        ....
    }

}

现在我在我的一个项目中使用相同的代码，但总是得到:

E/AndroidRuntime﹕ FATAL EXCEPTION: main
java.lang.NullPointerException 
at c.o.m.MainActivity$5.onCompleted(MainActivity.java:262)
at com.facebook.Request$1.onCompleted(Request.java:303)
at com.facebook.Request$4.run(Request.java:1726)
at android.os.Handler.handleCallback(Handler.java:615)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4921)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)

在这一行，我得到了NPE:

 String email = user.asMap().get("email").toString();

代码:

public class MainActivity extends Activity {

    Button btnFBLogin, btnGPLogin;

    private Session.StatusCallback sessionStatusCallback;
    private Session currentSession;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.screen_layout);

        sessionStatusCallback = new Session.StatusCallback() {

            @Override
            public void call(Session session, SessionState state,
                             Exception exception) {
                onSessionStateChange(session, state, exception);

            }
        };

        btnFBLogin = (Button) findViewById(R.id.loginFB);
        btnFBLogin.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // TODO Auto-generated method stub
                connectToFB();
            }
        }); 

    }

    public void connectToFB() {

        List<String> permissions = new ArrayList<String>();
        permissions.add("publish_actions");

        currentSession = new Session.Builder(this).build();
        currentSession.addCallback(sessionStatusCallback);

        Session.OpenRequest openRequest = new Session.OpenRequest(
                MainActivity.this);
        openRequest.setLoginBehavior(SessionLoginBehavior.SUPPRESS_SSO);
        openRequest.setRequestCode(Session.DEFAULT_AUTHORIZE_ACTIVITY_CODE);
        openRequest.setPermissions(permissions);
        currentSession.openForPublish(openRequest);

    }

    @Override
    public void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (currentSession != null) {
            currentSession
                    .onActivityResult(this, requestCode, resultCode, data);
        }
    }

    private void onSessionStateChange(Session session, SessionState state,
                                      Exception exception) {
        if (session != currentSession) {
            return;
        }

        if (state.isOpened()) {
            // Log in just happened.
            Toast.makeText(getApplicationContext(), "session opened",
                    Toast.LENGTH_SHORT).show();

            Request.executeMeRequestAsync(session, new Request.GraphUserCallback() {
                @Override
                public void onCompleted(GraphUser user, Response response) {
                    String fbId = user.getId();
                    String fbName = user.getName();
                    String gender = user.asMap().get("gender").toString();
                    String email = user.asMap().get("email").toString();
                    String first = user.asMap().get("first_name").toString();
                    String last = user.asMap().get("last_name").toString();

                    Toast.makeText(MainActivity.this, "EmailId:- "+email, Toast.LENGTH_LONG).show();
                }
            });

        } else if (state.isClosed()) {
            // Log out just happened. Update the UI.
            Toast.makeText(getApplicationContext(), "session closed",
                    Toast.LENGTH_SHORT).show();
        }
    }
}

可能是什么原因？为什么会这样？

最佳答案

有时用户可能没有在他们的个人资料中设置他们的电子邮件 ID，这是您通过 Android 在您的 Facebook 登录中获得的，这样会抛出空指针异常之类的错误。

因此，在从登录中获取电子邮件变量后，您应该在使用之前检查它是否为空，例如:

String email ="";
if(user.asMap().get("email") != null){
 email = user.asMap().get("email").toString();
}

关于android - Facebook onCompleted 电子邮件 java.lang.NullPointerException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/30389180/