void android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference

Question

The error started to appear only after I started using fragments in the project

here is my code..

public class MainActivity extends AppCompatActivity {  private Toolbar toolbar; private ViewPager mPager; private SlidingTabLayout mTabs; private MyPagerAdapter adapter;  public static final int product_result = 0;  @Override protected void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     setContentView(R.layout.activity_main);      toolbar = (Toolbar) findViewById(R.id.app_bar);      setSupportActionBar(toolbar);     assert getSupportActionBar() != null;     getSupportActionBar().setDisplayShowHomeEnabled(true);      NavigationDrawerFragment navigationDrawerFragment = (NavigationDrawerFragment)             getSupportFragmentManager().findFragmentById(R.id.fragment_nav_drawer);     navigationDrawerFragment.setUp(R.id.fragment_nav_drawer, (DrawerLayout) findViewById(R.id.drawer_layout), toolbar);      mPager = (ViewPager) findViewById(R.id.pager);     adapter = new MyPagerAdapter(getSupportFragmentManager());     mPager.setAdapter(adapter);      mTabs = (SlidingTabLayout) findViewById(R.id.tabs);     mTabs.setDistributeEvenly(true);     mTabs.setCustomTabView(R.layout.custom_tab_view, R.id.tabText);     int bgColor = ContextCompat.getColor(this, R.color.colorPrimary);     mTabs.setBackgroundColor(bgColor);     mTabs.setSelectedIndicatorColors(ContextCompat.getColor(MainActivity.this, R.color.colorAccent));     mTabs.invalidate();     mTabs.setViewPager(mPager); }   @Override public boolean onCreateOptionsMenu(Menu menu) {     getMenuInflater().inflate(R.menu.menu_main, menu);     return true; }  @Override public boolean onOptionsItemSelected(MenuItem item) {     int id = item.getItemId();     if (id == R.id.action_settings) {          return true;     }     if (id == R.id.navigate) {         startActivity(new Intent(this, SubActivity.class));     }     if (id == R.id.TabActivity) {         startActivity(new Intent(this, ActivityUsingTabLibrary.class));     }     if (id == R.id.VectorTest) {         startActivity(new Intent(this, VectorTestActivity.class));     }     return super.onOptionsItemSelected(item); }   class MyPagerAdapter extends FragmentStatePagerAdapter {     int icons[] = {R.drawable.home, R.drawable.hot_article, R.drawable.dizzy_person};      public MyPagerAdapter(FragmentManager fm) {         super(fm);     }      @Override     public Fragment getItem(int position) {          Fragment fragment = null;         switch(position){             case product_result:                 fragment = FragmentProduct.newInstance("","");                 break;         }         return fragment;     }      @Override     public CharSequence getPageTitle(int position) {         Drawable drawable = ResourcesCompat.getDrawable(getResources(), icons[position], null);         drawable.setBounds(0, 0, 36, 36);         ImageSpan imageSpan = new ImageSpan(drawable);         SpannableString spannableString = new SpannableString(" ");         spannableString.setSpan(imageSpan, 0, spannableString.length(), Spanned.SPAN_EXCLUSIVE_EXCLUSIVE);         return spannableString;     }      @Override     public int getCount() {         return 3;     } } 

}

this is my fragment.class where i m passing jsonObject toast.

public class FragmentProduct extends Fragment {  public static final String product_url = "http://oasisgroups.com/oApp/product.php";  private static final String ARG_PARAM1 = "param1"; private static final String ARG_PARAM2 = "param2";  private String mParam1; private String mParam2; private VolleySingleton volleySingleton; private ImageLoader imageLoader; private RequestQueue requestQueue;  public FragmentProduct() {     // Required empty public constructor }  public static FragmentProduct newInstance(String param1, String param2) {     FragmentProduct fragment = new FragmentProduct();     Bundle args = new Bundle();     args.putString(ARG_PARAM1, param1);     args.putString(ARG_PARAM2, param2);     fragment.setArguments(args);     return fragment; }  public static String getRequestUrl(int limit) {     return product_url + "&limit=" + limit; }  @Override public void onCreate(Bundle savedInstanceState) {     super.onCreate(savedInstanceState);     if (getArguments() != null) {         mParam1 = getArguments().getString(ARG_PARAM1);         mParam2 = getArguments().getString(ARG_PARAM2);     }      volleySingleton = VolleySingleton.getInstance();     requestQueue = volleySingleton.getmRequestQueue();     JsonObjectRequest request = new JsonObjectRequest(Request.Method.GET, getRequestUrl(10),             new Response.Listener<JSONObject>() {                 @Override                 public void onResponse(JSONObject response) {                     L.t(getActivity(), response.toString());                 }             }, new Response.ErrorListener() {         @Override         public void onErrorResponse(VolleyError error) {          }     });     requestQueue.add(request);  }  @Override public View onCreateView(LayoutInflater inflater, ViewGroup container,                          Bundle savedInstanceState) {     return inflater.inflate(R.layout.fragment_product, container, false); } 

}

stackTrace

02-29 12:10:01.047 17100-17100/com.mydesign.rockstar.materialdesignexample E/AndroidRuntime: FATAL EXCEPTION: main Process: com.mydesign.rockstar.materialdesignexample, PID: 17100 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v4.app.Fragment.setMenuVisibility(boolean)' on a null object reference     at android.support.v4.app.FragmentStatePagerAdapter.instantiateItem(FragmentStatePagerAdapter.java:116)     at android.support.v4.view.ViewPager.addNewItem(ViewPager.java:870)     at android.support.v4.view.ViewPager.populate(ViewPager.java:1086)     at android.support.v4.view.ViewPager.populate(ViewPager.java:952)     at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1474)     at android.view.View.measure(View.java:18804)     at android.widget.LinearLayout.measureVertical(LinearLayout.java:901)     at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)     at android.view.View.measure(View.java:18804)     at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:940)     at android.view.View.measure(View.java:18804)     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)     at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)     at android.support.v7.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:135)     at android.view.View.measure(View.java:18804)     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)     at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)     at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)     at android.view.View.measure(View.java:18804)     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)     at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)     at android.view.View.measure(View.java:18804)     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)     at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1465)     at android.widget.LinearLayout.measureVertical(LinearLayout.java:748)     at android.widget.LinearLayout.onMeasure(LinearLayout.java:630)     at android.view.View.measure(View.java:18804)     at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5954)     at android.widget.FrameLayout.onMeasure(FrameLayout.java:194)     at com.android.internal.policy.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2643)     at android.view.View.measure(View.java:18804)     at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2112)     at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1228)     at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1464)     at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1119)     at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6060)     at android.view.Choreographer$CallbackRecord.run(Choreographer.java:858)     at android.view.Choreographer.doCallbacks(Choreographer.java:670)     at android.view.Choreographer.doFrame(Choreographer.java:606)     at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:844)     at android.os.Handler.handleCallback(Handler.java:746)     at android.os.Handler.dispatchMessage(Handler.java:95)     at android.os.Looper.loop(Looper.java:148)     at android.app.ActivityThread.main(ActivityThread.java:5443)     at java.lang.reflect.Method.invoke(Native Method)     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:728)     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 

i also seen this same problem in this link and i apply his solution but it wont work for me.. i m still stuck, help me. so check my code and suggest me where what i missing.

Answer 1

oh yes.. i finally found my mistake.. first of all there is no mistake in my code. everything is right.

i have three tab layout and i m passing only for one tablayout and other two are getting null, so i must have to apply three switch case statement.

 public Fragment getItem(int position) {      Fragment fragment = null;     switch(position){         case product_result:             fragment = FragmentProduct.newInstance("","");             break;     }     return fragment; } 

instead

  public Fragment getItem(int num) {         Fragment fragment = null;         switch (num) {             case TAB_PRODUCT_RESULT:                 fragment = FragmentProduct.newInstance("", "");                 break;             case TAB_SECOND:                 fragment = MyFragment.getInstance(num);                 break;             case TAB_THIRD:                 fragment = MyFragment.getInstance(num);                 break;         }         return fragment;     } 

thats it..

Answer 2

I think the problem is in the public Fragment getItem(int position) method of your MyPagerAdapter. Your code snippet below is returning null fragments.

Fragment fragment = null; switch(position){     case product_result:         fragment = FragmentProduct.newInstance("","");         break;     } return fragment; 

You only get a real fragment for the position 0, because product_result is initialized to 0. In all other cases it returns null. Modify the above snippet of code to always return a fragment instance that is not null.