空指针异常：尝试从Facebook获取用户位置时

Question

I am trying to get user's location from Facebook, but getting Null Pointer Exception (NPE) and log looks like this:

D/dalvikvm(3116): GC_FOR_ALLOC freed 413K, 15% free 2863K/3336K, paused 32ms, total 32ms
W/System.err(3116): java.lang.NullPointerException
W/System.err(3116):     at com.example.loginfb.MainActivity$2.onUserInfoFetched(MainActivity.java:50)
W/System.err(3116):     at com.facebook.widget.LoginButton$2.onCompleted(LoginButton.java:770)
W/System.err(3116):     at com.facebook.Request$1.onCompleted(Request.java:280)
W/System.err(3116):     at com.facebook.Request$4.run(Request.java:1658)
W/System.err(3116):     at android.os.Handler.handleCallback(Handler.java:730)
W/System.err(3116):     at android.os.Handler.dispatchMessage(Handler.java:92)
W/System.err(3116):     at android.os.Looper.loop(Looper.java:137)
W/System.err(3116):     at android.app.ActivityThread.main(ActivityThread.java:5103)
W/System.err(3116):     at java.lang.reflect.Method.invokeNative(Native Method)
W/System.err(3116):     at java.lang.reflect.Method.invoke(Method.java:525)
W/System.err(3116):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737)
W/System.err(3116):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
W/System.err(3116):     at dalvik.system.NativeStart.main(Native Method)

MainActivity.java:-

public void onUserInfoFetched(GraphUser user) {
                try {
                if (user != null) {
                    String strName = user.getFirstName();
                    String strLocation = user.getLocation().toString();

                    textUserName.setText("Welcome, " + user.getName()) ;
                    textUserInformation.setText
                    (
                            "Name: " + strName + "\n"
                            +
                            "Location: " + strLocation
                    );

                   } else {
                       textUserName.setText("You are not Logged In");
                       textUserInformation.setText("");

                   }
                }
                    catch(Exception e)
                {
                    e.printStackTrace();
                }
            }
        });

I guess i am facing this issue, because has not given Location details on Facebook , but i want to show "Address not mentioned" in case user not provided to Facebook , along with other details.

Answer 1

Divide String strLocation = user.getLocation().toString(); in this:

Object userLocation = user.getLocation();
String strLocation = (userLocation != null)? userLocation.toString() : "Address not mentioned";

I don't know the type of the Location object but if user.getLocation() returns null , you will have a java.lang.NullPointerException with your code.