null object reference error in onCreate() method in Main Activity

Question

While working with fragments, I received this error. I have looked around a lot, here, various tutorials and all, but I just can't seem to tell, where I have gone wrong... I know this question has been asked repeatedly and all, but help me out!

Thanks in Advance! PS: Haven't posted a question before, so, Sorry in advance too!

Main Activity

 public class MainActivity extends FragmentActivity {

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

    if(savedInstanceState==null)
    {
        getSupportFragmentManager().beginTransaction().add(R.id.fragment,new MainActivityFragment()).commit();
    }

}

Fragment Activity

   public class MainActivityFragment extends Fragment {

       CalendarView cv;
       Context context;

       public MainActivityFragment() {
       }

       @Override
       public void onCreate(Bundle savedInstanceState) {
           super.onCreate(savedInstanceState);
           //getActivity().setContentView(R.layout.fragment_main);
       }

       @Override
       public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
           View view = inflater.inflate(R.layout.fragment_main, container, false);



       EditText editText = (EditText) view.findViewById(R.id.editText);
       editText.setOnClickListener(new View.OnClickListener() {
           @Override
           public void onClick(View v) {
            getCalendarView();
           }
       });

       return view;
   }

MainActivity Layout

<RelativeLayout
xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
android:paddingBottom="@dimen/activity_vertical_margin"
tools:context="com.example.ipt02.spotchecktrial1.MainActivity"
>
<TextView
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Is this coming?"/>



 <fragment
    android:id="@+id/fragment"
    class="com.example.ipt02.spotchecktrial1.MainActivityFragment"
    android:layout_width="match_parent"
    android:layout_height="match_parent" />

</RelativeLayout>

And finally the logcat:

java.lang.RuntimeException: Unable to start activity     ComponentInfo{com.example.ipt02.spotchecktrial1/com.example.ipt02.spotchecktrial1.MainActivity}:
java.lang.NullPointerException: Attempt to invoke interface method
'java.lang.String java.lang.CharSequence.toString()' on a null object
reference at
android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2325) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
at android.app.ActivityThread.access$800(ActivityThread.java:151) at
android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5257)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)
         Caused by: java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String java.lang.CharSequence.toString()' on a null object reference
at android.content.res.TypedArray.getString(TypedArray.java:176)
                at android.view.View.<init>(View.java:3992)
                at android.view.ViewGroup.<init>(ViewGroup.java:497)
                at android.view.ViewGroup.<init>(ViewGroup.java:493)
                at android.view.ViewGroup.<init>(ViewGroup.java:489)
                at android.view.ViewGroup.<init>(ViewGroup.java:485)
                at android.widget.FrameLayout.<init>(FrameLayout.java:103)
                at com.android.internal.policy.impl.PhoneWindow$DecorView.<init>(PhoneWindow.java:2226)
 at com.android.internal.policy.impl.PhoneWindow.generateDecor(PhoneWindow.java:3316)
at com.android.internal.policy.impl.PhoneWindow.installDecor(PhoneWindow.java:3669)
 at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:368)
at android.app.Activity.setContentView(Activity.java:2145) 
at com.example.ipt02.spotchecktrial1.MainActivity.onCreate(MainActivity.java:22)
                at android.app.Activity.performCreate(Activity.java:5990)
                at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1106)
                at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2278)
                at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2390)
                at android.app.ActivityThread.access$800(ActivityThread.java:151)
                at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1303)
                at android.os.Handler.dispatchMessage(Handler.java:102)
                at android.os.Looper.loop(Looper.java:135)
                at android.app.ActivityThread.main(ActivityThread.java:5257)
                at java.lang.reflect.Method.invoke(Native Method)
                at java.lang.reflect.Method.invoke(Method.java:372)
                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

EDIT - ADDED Strings.XML file

 <string name="hello_blank_fragment">Hello blank fragment</string>
<string-array name="location">
    <item>Amsterdam</item>
    <item>Dubai</item>
    <item>Great Coral Reef</item>
</string-array>

<string-array name="shift">
    <item>Shift - A</item>
    <item>Shift - B</item>
</string-array>

<string-array name="disciples">
    <item>Sammy</item>
    <item>John</item>
    <item>Arry</item>
    <item>Voldy</item>
</string-array>
<string name="title_activity_main">MainActivity</string>

Possible duplicate of [What is a NullPointerException, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) — Harshad Pansuriya, Jul 01 '16 at 06:49
@Ironman, i understand that it shows a NullPointerException, my doubt being why? I want the fragment to replace in the MainActivity, however that doesn't happen. Thus, the null pointer exception. So, how do i get around this? — Sherlock-and-MIB, Jul 01 '16 at 06:53
can you post your res/string.xml file. problem seems to be there.. — Mithilesh Izardar, Jul 01 '16 at 07:12
@MithileshIzardar uploaded as you requested. I don't see any problem... — Sherlock-and-MIB, Jul 01 '16 at 07:43

Harshad Pansuriya · Answer 1 · 2016-07-01T06:58:04.017

In your MainActivity use this way

Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    FragmentManager fm = getSupportFragmentManager();
    fragment = fm.findFragmentByTag("myFragmentTag");
    if (fragment == null) {
        FragmentTransaction ft = fm.beginTransaction();
        fragment =new MyFragment();
        ft.add(android.R.id.content,fragment,"myFragmentTag");
        ft.commit();
    }

}

null object reference error in onCreate() method in Main Activity

1 Answers1