我能够获得以下代码中显示的所有内容，但无法从用户个人资料中检索电子邮件。
我能为此做些什么？
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早些时候，我使用此来源获取Facebook用户的详细信息并正在获取数据（包括电子邮件），没有任何问题：
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，我正在 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？
答案 0 :(得分：0)
有时可能会发生这样的情况：用户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进入Facebook登录，因此抛出错误，如空指针异常。
所以在从Login获取之后你应该在使用电子邮件变量之前检查它是否为空如下：
String email ="";
if(user.asMap().get("email") != null){
email = user.asMap().get("email").toString();
}
答案 1 :(得分：0)
您需要将“email”添加到您需要的权限列表中，否则电子邮件将始终为null。我不知道你正在使用什么版本的sdk。最后一个你可以写：
Collection<String> mPermissions = new ArrayList<>();
mPermissions.add("email");
LoginManager mLoginManager = LoginManager.getInstance();
CallbackManager mCallbackManager = CallbackManager.Factory.create();
FbCallback fbCallback = new FbCallback(this);
mLoginManager.registerCallback(mCallbackManager, fbCallback);
[...]
mLoginManager.logInWithReadPermissions(this, mPermissions);
顺便说一句......请记住，用户可以撤销权限，也可以在登录时无权授予权限。