android.content.Context.getPackageName()' on a null object reference
AndroidAndroid FragmentsFragmentAndroid Problem Overview
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)
Android Solutions
Solution 1 - Android
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);
Solution 2 - Android
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.
Solution 3 - Android
android API level 23.
Use
> getContext()
instead of
> getActivity()
getActivity() gives the parent Activity, a Context object
Here You can use
> MyActivity.this
instead of
> getActivity() / getApplicationContext()
Solution 4 - Android
I had the same problem trying to show a Toast in a fragment.
After some debugging I found out that I was removing the fragment before calling:
Toast.makeText(getContext(), "text", Toast.LENGTH_SHORT).show();
Because the fragment had been removed, the context became null, causing the exception.
Simple solution: call the getContext()
before removing the fragment.
Solution 5 - Android
In my case the error occurred inside a Fragment
on this line:
Intent intent = new Intent(getActivity(), SecondaryActivity.class);
It happened when I double clicked on an item which triggered the code above so two SecondaryActivity.class
activities were launched at the same time, one on top of the other. I closed the top SecondaryActivity.class
activity by pressing back button which triggered a call to getActivity()
in the SecondaryActivity.class
which came to foreground. The call to getActivity()
returned null
.
It's some kind of weird Android bug so it usually should not happen.
You can block the clicks after the user clicked once.
Solution 6 - Android
In my case I had a onCLick method in a recyclerview adapter,Context context; at the beginning.
holder.cTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(context, StoryActivity.class);
intent.putExtra("STORY", mComments.get(position));
context.startActivity(intent);
}
});
And i changed to get the context from the current view
holder.cTextView.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Intent intent = new Intent(v.getContext(), StoryActivity.class);
intent.putExtra("STORY", mComments.get(position));
v.getContext().startActivity(intent);
}
});
Solution 7 - Android
For me the problem was that I was passing Activity to the constructor, not Context
public Adapter(Activity activity, List<MediaItem> items, boolean can) {
mItems = items;
canEdit = can;
mActivity = activity;
}
and using this activity to getDefaultSharedPreferences(), so I changed the Activity to Context and I was still calling the Adapter constructor with MainActivity.this
Solution 8 - Android
You only need to do this:
Intent myIntent = new Intent(MainActivity.this, nextActivity.class);
Solution 9 - Android
My class is not extends to Activiti. I solved the problem this way.
class MyOnBindViewHolder : LogicViewAdapterModel.LogicAdapter {
...
holder.title.setOnClickListener({v->
v.context.startActivity(Intent(context, HomeActivity::class.java))
})
...
}
Solution 10 - Android
Put fragment name before the activity
Intent mIntent = new Intent(SigninFragment.this.getActivity(),MusicHome.class);
Solution 11 - Android
You solve the issue with a try/ catch. This crash happens when user close the app before the start intent.
try
{
Intent mIntent = new Intent(getActivity(),MusicHome.class);
mIntent.putExtra("SigninFragment.user_details", bundle);
startActivity(mIntent);
}
catch (Exception e) {
e.printStackTrace();
}
Solution 12 - Android
You can solve your problem easily and use your activity anywhere in the activity, just store activity like this:
public class MainActivity extends AppCompatActivity{
Context context = this;
protected void onCreate(Bundle savedInstanceState) {....}
AnotherClass {
Intent intent = new Intent(context, ExampleActivity.class);
intent.putExtra("key", "value");
startActivity(intent);
}
}
Solution 13 - Android
Due to onAttach
is deprecated in API23 and above...
In my Fragment, I declare and set parentActivity
before hand everytime when I go into Fragment. Most likely happen due to when we pressed back button caused the context to become null. Therefore below is my solution.
private Activity parentActivity;
public void onStart(){
super.onStart();
parentActivity = getActivity();
//...
}
Solution 14 - Android
public MessageAdapter(Context context, List<Messages> mMessageList) {
this.mContext = context;
this.mMessageList = mMessageList;
}
Solution 15 - Android
Use can use in global
Context context;
and create a constructor and passing the context. LoginClass is name of the class
LoginClass(Context context)
{this.context=context;}
and also when we call the class then use getApplicationContext
like
LoginClass lclass = new LoginClass(getApplicationContext)
thats it.
Solution 16 - Android
In Kotlin
lateinit var views:View?
override fun onCreateView(
inflater: LayoutInflater, container: ViewGroup?,
savedInstanceState: Bundle?
): View? {
// Inflate the layout for this fragment
views=inflater.inflate(R.layout.fragment_dashboard, container, false)
Toast.makeText(views.context ,"hello",Toast.LENGTH_LONG).show()
return views;
}
Solution 17 - Android
Sometimes startActivity
method throws an exception like especially in Fragments
:
Calling startActivity()
from outside of an Activity
context requires the FLAG_ACTIVITY_NEW_TASK
flag. Is this really what you want?
So you should intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK)
method