在Android应用中检索Facebook用户的个人资料图片时为空指针

Question

I have an app that lets the user log in through Facebook SDK. This works fine. I am trying to display that user's profile picture on a welcome activity along with their name. I can successfully get their name and display it, but I get a null pointer when I try to get their profile picture. This is the code snippet:

if (user != null) {
    TextView welcome = (TextView) findViewById(R.id.textView2);
    welcome.setText(user.getName());
    ProfilePictureView userPicture = (ProfilePictureView) findViewById(R.id.imageView1);
    userPicture.setProfileId(user.getId());
}

I am successfully retrieving and displaying the user's name by using welcome.setText(user.getName()); so I know that the user != null. And the error is on this line: userPicture.setProfileId(user.getId()); Any ideas? Thanks.

Full Code

public class WelcomeScreen extends ActionBarActivity {

TextView tv;

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

    tv = (TextView) findViewById(R.id.textView1);
    // Session session = Session.getActiveSession();
    if (Session.getActiveSession() != null) {
        Log.d("In?", String.valueOf(Session.getActiveSession().isOpened()));
    } else {
        Log.d("Session is ", "null");
    }

    if (Session.getActiveSession() != null
            || !Session.getActiveSession().isClosed()) {
        Session.openActiveSession(WelcomeScreen.this, true,
                new Session.StatusCallback() {

                    // callback when session changes state
                    @Override
                    public void call(Session session, SessionState state,
                            Exception exception) {
                        if (session.isOpened()) {

                            // make request to the /me API
                            Request.newMeRequest(session,
                                    new Request.GraphUserCallback() {

                                        // callback after Graph API
                                        // response with user
                                        // object
                                        @Override
                                        public void onCompleted(
                                                GraphUser user,
                                                Response response) {
                                            if (user != null) {
                                                TextView welcome = (TextView) findViewById(R.id.textView2);
                                                welcome.setText(user
                                                        .getName());
                                                ProfilePictureView userPicture = (ProfilePictureView) findViewById(R.id.imageView1);
                                                userPicture.setProfileId(user.getId());
                                            }
                                        }
                                    }).executeAsync();
                            Log.d("In?", String.valueOf(Session
                                    .getActiveSession().isOpened()));
                            session = Session.getActiveSession();
                            if (session == null) {
                                Log.d("Session is", "null");
                            }
                        }
                    }
                });
    }

}

}

Logcat

07-24 13:44:15.061: E/AndroidRuntime(10953): FATAL EXCEPTION: main
07-24 13:44:15.061: E/AndroidRuntime(10953): java.lang.NullPointerException
07-24 13:44:15.061: E/AndroidRuntime(10953):    at com.example.test.WelcomeScreen$1$1.onCompleted(WelcomeScreen.java:79)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at com.facebook.Request$1.onCompleted(Request.java:303)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at com.facebook.Request$4.run(Request.java:1726)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at android.os.Handler.handleCallback(Handler.java:730)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at android.os.Handler.dispatchMessage(Handler.java:92)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at android.os.Looper.loop(Looper.java:137)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at android.app.ActivityThread.main(ActivityThread.java:5289)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at java.lang.reflect.Method.invokeNative(Native Method)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at java.lang.reflect.Method.invoke(Method.java:525)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:739)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:555)
07-24 13:44:15.061: E/AndroidRuntime(10953):    at dalvik.system.NativeStart.main(Native Method)

EDIT

I've been looking around and I think I might need to request permission to access the user's photos? If this is the case, any ideas how I can? Thanks.

Answer 1

You have set the layout to activity_welcome_screen using setContentView .

But it is that you do not have the id imageview1 in that layout.

So for line,

ProfilePictureView userPicture = (ProfilePictureView) findViewById(R.id.imageView1);

The userPicture is null.

And the exception is when you do,

userPicture.setProfileId(user.getId());

That is - you are calling method setProfileId on something which is null.

So NullPointerException .