ListView не инициализируется

Question

Это подводит меня прямо к стене прямо сейчас. У меня есть два фрагмента с ListViews, оба из которых используют . Один из них прекрасно работает, а другой - нет.

Вот рабочий Фрагмент:

//IRRELEVANT CODE ABOVE 
@BindView(R.id.exerciseListView1) 
ListView exerciseListView; 

/** 
* Mandatory empty constructor for the fragment manager to instantiate the 
* fragment (e.g. upon screen orientation changes). 
*/ 
public ExerciseFragment() { 
} 

@SuppressWarnings("unused") 
public static ExerciseFragment newInstance(int columnCount) { 
    ExerciseFragment fragment = new ExerciseFragment(); 
    Bundle args = new Bundle(); 
    args.putInt(ARG_COLUMN_COUNT, columnCount); 
    fragment.setArguments(args); 
    return fragment; 
} 

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

    if (getArguments() != null) { 
     mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT); 
    } 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_exercise_list, container, false); 
    unbinder = ButterKnife.bind(this, view); 

    ListItem[] exercises = { 
      new ListItem(" 1. Learning Names & Faces", "This exercise will teach you how to learn people's names."), 
      new ListItem(" 2. Paying Attention", "This exercise will test how well you pay attention."), 
      new ListItem(" 3. Memory Recall", "This exercise will help you improve your recall skills.") 
    }; 

    mAdapter = new ArrayAdapter<ListItem>(view.getContext(), R.layout.mylist, exercises); 
    exerciseListView.setAdapter(mAdapter); 
    exerciseListView.setOnItemClickListener(new ListView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, 
           long id) { 
      String item = ((TextView) view).getText().toString(); 
      Log.d("ExercisesActivity", item + " #" + Integer.toString(position) + " selected"); 
      //Switch statements won't take longs, thankfully there's the position variable 
      switch (position) { 
       case 0: 
        startActivity(new Intent(getContext(), LearningNamesActivity.class)); 
        break; 
       case 1: 
        startActivity(new Intent(getContext(), PayingAttentionActivity.class)); 
        break; 
       case 2: 
        startActivity(new Intent(getContext(), MemoryRecallActivity.class)); 
        break; 
      } 
     } 
    }); 

    return view; 
} 

И вот один, что не будет работать:

//IRRELEVANT CODE ABOVE 
@BindView(R.id.informationListView) 
ListView informationList; 
/** 
* Mandatory empty constructor for the fragment manager to instantiate the 
* fragment (e.g. upon screen orientation changes). 
*/ 
public InformationFragment() { 
} 

// TODO: Customize parameter initialization 
@SuppressWarnings("unused") 
public static InformationFragment newInstance(int columnCount) { 
    InformationFragment fragment = new InformationFragment(); 
    Bundle args = new Bundle(); 
    args.putInt(ARG_COLUMN_COUNT, columnCount); 
    fragment.setArguments(args); 
    return fragment; 
} 

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

    if (getArguments() != null) { 
     mColumnCount = getArguments().getInt(ARG_COLUMN_COUNT); 
    } 
} 

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
         Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_information_list, container, false); 
    unbinder = ButterKnife.bind(getContext(), view); 

    ListItem[] exercises = { 
      new ListItem("1. Tell me about memory", ""), 
      new ListItem("2. What can go wrong with my memory", ""), 
      new ListItem("3. Helpful tips to improve my memory", "") 
    }; 
    mAdapter = new ArrayAdapter<>(view.getContext(), R.layout.mylist, exercises); 
informationList.setAdapter(mAdapter); 
informationList.setOnItemClickListener(new AdapterView.OnItemClickListener() { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, long id) { 
      switch (position) { 
       case 0: 
        startActivity(new Intent(getContext(), LearnAboutMemoryActivity.class)); 
        break; 
       case 1: 
        startActivity(new Intent(getContext(), WhatCanGoWrongActivity.class)); 
        break; 
       case 2: 
        //TODO: Use HelpfulTipsActivity as an "all-purpose" activity for holding tip Fragments 
        startActivity(new Intent(getContext(), HelpfulTipsActivity.class)); 
        break; 
      } 
     } 
}); 

return view; 

Вот журнал ошибок:

06-17 12:20:15.674 13182-13182/com.tommy.mastersproject E/AndroidRuntime: FATAL EXCEPTION: main                   Process: com.tommy.mastersproject, PID: 13182 
Theme: themes:{com.android.settings=overlay:com.cyngn.hexo, default=overlay:system, iconPack:system, fontPkg:system, com.android.systemui=overlay:system, com.android.systemui.navbar=overlay:system} 
                      java.lang.RuntimeException: Unable to start activity ComponentInfo{com.tommy.mastersproject/com.tommy.mastersproject.activities.InformationActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510) 
at android.app.ActivityThread.-wrap11(ActivityThread.java) 
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363) 
at android.os.Handler.dispatchMessage(Handler.java:102) 
at android.os.Looper.loop(Looper.java:148) 
at android.app.ActivityThread.main(ActivityThread.java:5461) 
at java.lang.reflect.Method.invoke(Native Method) 
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) 
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) 
Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ListView.setAdapter(android.widget.ListAdapter)' on a null object reference 
at com.tommy.mastersproject.fragments.InformationFragment.onCreateView(InformationFragment.java:90) 
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1974) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1067) 
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1252) 
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:742) 
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1617) 
at android.support.v4.app.FragmentController.execPendingActions(FragmentController.java:339) 
at android.support.v4.app.FragmentActivity.onStart(FragmentActivity.java:601) 
at android.app.Instrumentation.callActivityOnStart(Instrumentation.java:1238) 
at android.app.Activity.performStart(Activity.java:6268) 
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2413) 
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)  
at android.app.ActivityThread.-wrap11(ActivityThread.java)  
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)  
at android.os.Handler.dispatchMessage(Handler.java:102)  
at android.os.Looper.loop(Looper.java:148)  
at android.app.ActivityThread.main(ActivityThread.java:5461)  
at java.lang.reflect.Method.invoke(Native Method)  
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)  
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)  

Вот Фрагменты 'соответствующие файлы макета: Работа правильно

<?xml version="1.0" encoding="utf-8"?> 
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent"> 
    <ListView 
     android:id="@+id/exerciseListView1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content"/> 
</RelativeLayout> 

Не работает должным образом

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" 
android:layout_width="match_parent" 
android:layout_height="match_parent"> 
    <ListView 
     android:id="@+id/informationListView" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" /> 
</RelativeLayout> 

Было ли что-то в рабочем Fragment, что я забыл поставить в один, который не работает?

Answer 1

Я думаю, что проблема в InformationFragment внутри onCreateView():

@Override 
public View onCreateView(LayoutInflater inflater, ViewGroup container, 
        Bundle savedInstanceState) { 
    View view = inflater.inflate(R.layout.fragment_information_list, container, false); 
    unbinder = ButterKnife.bind(this, view); 

    ListItem[] exercises = { 
     new ListItem("1. Tell me about memory", ""), 
     new ListItem("2. What can go wrong with my memory", ""), 
     new ListItem("3. Helpful tips to improve my memory", "") 
    }; 
    // rest of your code 

Проблема:

Хотя связывание зрения вы использовали getContext() .so ваш informationList ListView остается Null и вы получение NullPointerException Удалить getContext() instea d add this.