android.content.Context.getPackageName()' on a null object reference

Question

I am working with Fragments which implements an interface.

public class SigninFragment extends Fragment implements SigninInterface  

The interface's method implementation in the fragment class is as follows.

@Override public void afterSubmitClicked(String userId, Bundle bundle) {      Log.d(TAG,"Calling time afterSubmitClicked called"+bundle);          if(!userId.equals("-1")){         //Logged in successfully         //Move to MusicHome                  Intent mIntent = new Intent(getActivity(),MusicHome.class);         mIntent.putExtra("SigninFragment.user_details", bundle);         startActivity(mIntent);              }else{         //Logging in failed         //show error dialog     }      } 

This method is called after exectuting a AsynchronousTask (which extends AsyncTask) class.

But I am getting crash. And the error message shows

java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 

Logcat

   02-14 16:37:04.648: E/AndroidRuntime(28177): Process: com.raaga.android, PID: 28177 02-14 16:37:04.648: E/AndroidRuntime(28177): java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.content.ComponentName.<init>(ComponentName.java:77) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.content.Intent.<init>(Intent.java:3996) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at com.raaga.fragments.SigninFragment.afterSubmitClicked(SigninFragment.java:152) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at com.raaga.asynctask.SignInAsyncTask.onPostExecute(SignInAsyncTask.java:92) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at com.raaga.asynctask.SignInAsyncTask.onPostExecute(SignInAsyncTask.java:1) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.os.AsyncTask.finish(AsyncTask.java:632) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.os.AsyncTask.access$600(AsyncTask.java:177) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.os.Handler.dispatchMessage(Handler.java:102) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.os.Looper.loop(Looper.java:135) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at android.app.ActivityThread.main(ActivityThread.java:5221) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at java.lang.reflect.Method.invoke(Native Method) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at java.lang.reflect.Method.invoke(Method.java:372) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) 02-14 16:37:04.648: E/AndroidRuntime(28177):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 

Answer 1

I have found the mistake what I did. We need to get the activity instance from the override method OnAttach() For example,

public MainActivity activity;  @Override public void onAttach(Activity activity){     this.activity = activity; } 

Then pass the activity as context as following.

Intent mIntent = new Intent(activity, MusicHome.class); 

Answer 2

The answers to this question helped me find my problem, but my source was different, so hopefully this can shed light on someone finding this page searching for answers to the 'random' context crash:

I had specified a SharedPreferences object, and tried to instantiate it at it's class-level declaration, like so:

public class MyFragment extends FragmentActivity {     private SharedPreferences sharedPref =         PreferenceManager.getDefaultSharedPreferences(this);  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     //... 

Referencing this before the onCreate caused the "java.lang.NullPointerException: Attempt to invoke virtual method 'java.lang.String android.content.Context.getPackageName()' on a null object reference" error for me.

Instantiating the object inside the onCreate() solved my problem, like so:

public class MyFragment extends FragmentActivity {     private SharedPreferences sharedPref;      @Override     protected void onCreate(Bundle savedInstanceState) {         super.onCreate(savedInstanceState);         //...         sharedPref = PreferenceManager.getDefaultSharedPreferences(this); 

Hope that helps.