एंड्रॉयड प्रयास एक अशक्त वस्तु संदर्भ

Question

यहाँ पर आभासी विधि आह्वान करने के लिए 'शून्य android.support.v4.app.Fragment.setMenuVisibility (बुलियन)' त्रुटि से भरा स्टैक ट्रेस है प्रोजेक्ट में टुकड़ों का उपयोग शुरू करने के बाद ही दिखाई देने के लिए, क्योंकि मैं JSON फ़ीड्स देना चाहता हूं। जब मैं टैब्स बनाने से पहले ठीक था, NavigationDrawer आदि

MainActivity.java

सार्वजनिक वर्ग MainActivity फैली ActionBarActivity लागू करता MaterialTabListener {

private Toolbar mToolbar; 
private NavigationDrawerFragment mDrawerFragment; 
private DrawerLayout mDrawerLayout; 

private MaterialTabHost mTabHost; 
private ViewPager mViewPager; 

public static final int SERVICES_ALL = 1; 
public static final int SERVICES_FEATURED = 2; 
public static final int SERVICES_NEW = 3; 

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

    mToolbar = (Toolbar) findViewById(R.id.app_bar); 
    setSupportActionBar(mToolbar); 
    getSupportActionBar().setDisplayShowHomeEnabled(true); 

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
    mDrawerFragment = (NavigationDrawerFragment) getSupportFragmentManager().findFragmentById(R.id.fragment_navigation_drawer); 
    mDrawerFragment.setUp(R.id.fragment_navigation_drawer, mDrawerLayout, mToolbar); 

    mTabHost = (MaterialTabHost) findViewById(R.id.materialTabHost); 
    mViewPager = (ViewPager) findViewById(R.id.viewPager); 

    MyPagerAdapter adapter = new MyPagerAdapter(getSupportFragmentManager()); 
    mViewPager.setAdapter(adapter); 
    mViewPager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener(){ 
     @Override 
     public void onPageSelected(int position) { 
      mTabHost.setSelectedNavigationItem(position); 
     } 
    }); 

    for(int i=0; i<adapter.getCount(); i++){ 
     mTabHost.addTab(
       mTabHost.newTab(). 
         setText(adapter.getPageTitle(i)). 
         setTabListener(this) 
     ); 
    } 
} 

@Override 
public void onTabSelected(MaterialTab materialTab) { 
    mViewPager.setCurrentItem(materialTab.getPosition()); 
} 

@Override 
public void onTabReselected(MaterialTab materialTab) { 

} 

@Override 
public void onTabUnselected(MaterialTab materialTab) { 

} 

private class MyPagerAdapter extends FragmentStatePagerAdapter{ 
    FragmentManager fragmentManager; 

    public MyPagerAdapter(FragmentManager fm) { 
     super(fm); 
     fragmentManager = fm; 
    } 

    @Override 
    public Fragment getItem(int num) { 
     Fragment fragment = null; 
     switch (num){ 
      case SERVICES_ALL: 
       fragment = FragmentAll.newInstance("",""); 
       break; 
      case SERVICES_FEATURED: 
       fragment = FragmentFeatured.newInstance("",""); 
       break; 
      case SERVICES_NEW: 
       fragment = FragmentNew.newInstance("",""); 
       break; 
     } 
     return fragment; 
    } 

    @Override 
    public int getCount() { 
     return 3; 
    } 

    public CharSequence getPageTitle(int position){ 
     return getResources().getStringArray(R.array.tabs)[position]; 
    } 
} 

@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) { 
     Toast.makeText(this, "Hey you just hit " + item.getTitle(), Toast.LENGTH_LONG).show(); 
     return true; 
    } 

    if (id == R.id.action_next) { 
     startActivity(new Intent(this, DetailActivity.class)); 
    } 

    return super.onOptionsItemSelected(item); 
} 

}

FragmentAll.java (अन्य 2 टुकड़े FragmentAll के समान हैं।)

सार्वजनिक वर्ग FragmentAll फैली टुकड़ा {

private static final String ARG_PARAM1 = "param1"; 
private static final String ARG_PARAM2 = "param2"; 

private String mParam1; 
private String mParam2; 

public static FragmentAll newInstance(String param1, String param2) { 
    FragmentAll fragment = new FragmentAll(); 
    Bundle args = new Bundle(); 
    args.putString(ARG_PARAM1, param1); 
    args.putString(ARG_PARAM2, param2); 
    fragment.setArguments(args); 
    return fragment; 
} 

public FragmentAll() { 
    // Required empty public constructor 
} 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    if (getArguments() != null) { 
     mParam1 = getArguments().getString(ARG_PARAM1); 
     mParam2 = getArguments().getString(ARG_PARAM2); 
    } 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    // Inflate the layout for this fragment 
    return inflater.inflate(R.layout.fragment_all, container, false); 
} 
} 

स्टैकट्रेस: ​​

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:836) 
      at android.support.v4.view.ViewPager.populate(ViewPager.java:986) 
      at android.support.v4.view.ViewPager.populate(ViewPager.java:918) 
      at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1440) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at android.support.v7.internal.widget.ContentFrameLayout.onMeasure(ContentFrameLayout.java:124) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436) 
      at android.widget.LinearLayout.measureVertical(LinearLayout.java:722) 
      at android.widget.LinearLayout.onMeasure(LinearLayout.java:613) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463) 
      at android.widget.FrameLayout.onMeasure(FrameLayout.java:430) 
      at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560) 
      at android.view.View.measure(View.java:17430) 
      at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001) 
      at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166) 
      at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372) 
      at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054) 
      at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779) 
      at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767) 
      at android.view.Choreographer.doCallbacks(Choreographer.java:580) 
      at android.view.Choreographer.doFrame(Choreographer.java:550) 
      at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753) 
      at android.os.Handler.handleCallback(Handler.java:739) 
      at android.os.Handler.dispatchMessage(Handler.java:95) 
      at android.os.Looper.loop(Looper.java:135) 
      at android.app.ActivityThread.main(ActivityThread.java:5221) 
      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:899) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694) 

Answer 1

public static final int SERVICES_ALL = 1; 
public static final int SERVICES_FEATURED = 2; 
public static final int SERVICES_NEW = 3; 

public static final int SERVICES_ALL = 0; 
public static final int SERVICES_FEATURED = 1; 
public static final int SERVICES_NEW = 2; 

getItem होना चाहिए 0-आधारित सूचकांक, में इसका मतलब है कि जो है आपका कोड, आपके एडाप्टर के case 0 कभी मेल नहीं खाता है, और उस स्थिति में आप अपूर्ण खंड को वापस कर रहे हैं क्योंकि अपवाद