Bug con ViewPager e RecyclerView

Question

Sto usando un ViewPager con un RecyclerView all'interno del primo frammento di ViewPager.

Quando si scorre da sinistra a destra, nessun errore. Ma quando ho scorrere da destra a sinistra (dalla # 2 # 1 frammento del ViewPager), verifica il seguente errore:

05-10 20:21:07.546 20002-20002/com.graffiti75.android.worldremit E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    Process: com.graffiti75.android.worldremit, PID: 20002 
    java.lang.NullPointerException: Attempt to invoke virtual method 'boolean android.support.v7.widget.RecyclerView$LayoutManager.canScrollHorizontally()' on a null object reference 
      at android.support.v7.widget.RecyclerView.onInterceptTouchEvent(RecyclerView.java:1819) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:1960) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at android.view.ViewGroup.dispatchTransformedTouchEvent(ViewGroup.java:2405) 
      at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:2049) 
      at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:2369) 
      at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1719) 
      at android.app.Activity.dispatchTouchEvent(Activity.java:2742) 
      at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:2330) 
      at android.view.View.dispatchPointerEvent(View.java:8666) 
      at android.view.ViewRootImpl$ViewPostImeInputStage.processPointerEvent(ViewRootImpl.java:4123) 
      at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3989) 
      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544) 
      at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597) 
      at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563) 
      at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3680) 
      at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571) 
      at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3737) 
      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544) 
      at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3597) 
      at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3563) 
      at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3571) 
      at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3544) 
      at android.view.ViewRootImpl.deliverInputEvent(ViewRootImpl.java:5807) 
      at android.view.ViewRootImpl.doProcessInputEvents(ViewRootImpl.java:5781) 
      at android.view.ViewRootImpl.enqueueInputEvent(ViewRootImpl.java:5752) 
      at android.view.ViewRootImpl$WindowInputEventReceiver.onInputEvent(ViewRootImpl.java:5897) 
      at android.view.InputEventReceiver.dispatchInputEvent(InputEventReceiver.java:185) 
      at android.os.MessageQueue.nativePollOnce(Native Method) 
      at android.os.MessageQueue.next(MessageQueue.java:143) 
      at android.os.Looper.loop(Looper.java:122) 
      at android.app.ActivityThread.main(ActivityThread.java:5254) 
      at java.lang.reflect.Method.invoke(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:372) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698) 
05-10 20:21:07.549  550-7690/? W/ActivityManager﹕ Force finishing activity 1 com.graffiti75.android.worldremit/.activity.WalkthroughActivity 

Questo è l'errore: java.lang.NullPointerException: Tentativo di richiamare il metodo virtuale ' booleano android.support.v7.widget.RecyclerView $ LayoutManager.canScrollHorizontally() 'su un oggetto nullo di riferimento

Il metodo seguente è il primo frammento del mio ViewPager. Quando commento le linee in cui viene chiamato RecyclerView, non si verificano errori. Ma ho bisogno di questo RecyclerView per sfogliare i miei contatti! Quindi credo che questo dimostra l'errore si verifica in quelle righe ...

public class ContactListFragment extends Fragment { 

    //-------------------------------------------------- 
    // Constructor 
    //-------------------------------------------------- 

    public static ContactListFragment newInstance() { 
     ContactListFragment fragment = new ContactListFragment(); 
     Bundle args = new Bundle(); 
     fragment.setArguments(args); 
     return fragment; 
    } 

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

    //-------------------------------------------------- 
    // Fragment Life Cycle 
    //-------------------------------------------------- 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
    } 

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

     // Get data. 
     List<String> nameList = new ArrayList<String>(); 
     Cursor cursor = getContacts(); 
     while (cursor.moveToNext()) { 
      String name = cursor.getString(cursor.getColumnIndex(ContactsContract.Contacts.DISPLAY_NAME)); 
      nameList.add(name); 
     } 

     // Setup list. 
     RecyclerView recyclerView = (RecyclerView) v.findViewById(R.id.id_recycler_view); 
     recyclerView.setHasFixedSize(true); 

     Activity activity = getActivity(); 
     final LinearLayoutManager layoutManager = new LinearLayoutManager(activity); 
     layoutManager.setOrientation(LinearLayoutManager.VERTICAL); 
     recyclerView.setLayoutManager(layoutManager); 

     recyclerView.setItemAnimator(new DefaultItemAnimator()); 
     recyclerView.setAdapter(new ContactListAdapter(getActivity(), nameList)); 

     return v; 
    } 

    //-------------------------------------------------- 
    // Methods 
    //-------------------------------------------------- 

    private Cursor getContacts() { 
     // Run query. 
     Uri uri = ContactsContract.Contacts.CONTENT_URI; 
     String[] projection = new String[] { ContactsContract.Contacts._ID, ContactsContract.Contacts.DISPLAY_NAME }; 
     String selection = ContactsContract.Contacts.IN_VISIBLE_GROUP + " = '" + ("1") + "'"; 
     String[] selectionArgs = null; 
     //String sortOrder = ContactsContract.Contacts._ID + " COLLATE LOCALIZED ASC"; 
     String sortOrder = ContactsContract.Contacts.DISPLAY_NAME + " COLLATE LOCALIZED ASC"; 

     return getActivity().managedQuery(uri, projection, selection, selectionArgs, sortOrder); 
    } 
} 

Coloro riga sotto: // lista Setup.

Ho ricercato molto in Google e non sono riuscito a trovare un modo per risolvere questi errori.

Qualcuno ha una supposizione?

Answer 1

Ho avuto lo stesso problema, ho creato sottoclasse da ViewPager, che gestisce questo errore. Spero che questo ti possa aiutare.

public class HackyViewPager extends ViewPager { 


public HackyViewPager(Context context) { 
    super(context); 
} 

public HackyViewPager(Context context, AttributeSet attrs) { 
    super(context, attrs); 
} 

@Override 
public boolean onInterceptTouchEvent(MotionEvent ev) { 
    try { 
     return super.onInterceptTouchEvent(ev); 
    } catch (Throwable t) { 
     t.printStackTrace(); 
     return false; 
    } 
}}