Как добавить пользовательский listView в фрагмент?

Question

Я пытаюсь создать собственный список в моем фрагменте, но получаю ошибку с нулевым указателем, как я могу исправить это. Я новичок.

listmain.xml:

<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:layout_marginLeft="5dp" 
    android:layout_marginRight="5dp" 
    android:layout_marginTop="5dp" 
    tools:context=".MainActivity" > 

    <ListView 
     android:id="@+id/list" 
     android:layout_width="fill_parent" 
     android:layout_height="wrap_content" 
     android:divider="@null" 
     android:dividerHeight="5dp" 
     android:listSelector="@drawable/list_row_selector" /> 

</RelativeLayout> 

activity_main.xml:

<android.support.v4.widget.DrawerLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    android:id="@+id/drawer_layout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent"> 

    <!-- Framelayout to display Fragments --> 
    <FrameLayout 
     android:id="@+id/frame_container" 
     android:layout_width="match_parent" 
     android:layout_height="match_parent" > 
    </FrameLayout> 

    <!-- Listview to display slider menu --> 
    <ListView 
     android:id="@+id/list_slidermenu" 
     android:layout_width="240dp" 
     android:layout_height="match_parent" 
     android:layout_gravity="start" 
     android:choiceMode="singleChoice" 
     android:divider="@color/list_divider" 
     android:dividerHeight="1dp"   
     android:listSelector="@drawable/list_selector" 
     android:background="@color/list_background"/> 
</android.support.v4.widget.DrawerLayout> 

моя основная деятельность это для навигации ящик:

public class MainActivity extends Activity { 
    private DrawerLayout mDrawerLayout; 
    private ListView mDrawerList; 
    private ActionBarDrawerToggle mDrawerToggle; 

    // nav drawer title 
    private CharSequence mDrawerTitle; 

    // used to store app title 
    private CharSequence mTitle; 

    // slide menu items 
    private String[] navMenuTitles; 
    private TypedArray navMenuIcons; 

    private ArrayList<NavDrawerItem> navDrawerItems; 
    private NavDrawerListAdapter adapter; 

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

     mTitle = mDrawerTitle = getTitle(); 

     // load slide menu items 
     navMenuTitles = getResources().getStringArray(R.array.nav_drawer_items); 

     // nav drawer icons from resources 
     navMenuIcons = getResources() 
       .obtainTypedArray(R.array.nav_drawer_icons); 

     mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout); 
     mDrawerList = (ListView) findViewById(R.id.list_slidermenu); 

     navDrawerItems = new ArrayList<NavDrawerItem>(); 

     // adding nav drawer items to array 
     // Home 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[0], navMenuIcons.getResourceId(0, -1))); 
     // Find People 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[1], navMenuIcons.getResourceId(1, -1))); 
     // Photos 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[2], navMenuIcons.getResourceId(2, -1))); 
     // Communities, Will add a counter here 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[3], navMenuIcons.getResourceId(3, -1))); 
     // Pages 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[4], navMenuIcons.getResourceId(4, -1))); 
     // What's hot, We will add a counter here 
     navDrawerItems.add(new NavDrawerItem(navMenuTitles[5], navMenuIcons.getResourceId(5, -1))); 


     // Recycle the typed array 
     navMenuIcons.recycle(); 

     mDrawerList.setOnItemClickListener(new SlideMenuClickListener()); 

     // setting the nav drawer list adapter 
     adapter = new NavDrawerListAdapter(getApplicationContext(), 
       navDrawerItems); 
     mDrawerList.setAdapter(adapter); 

     // enabling action bar app icon and behaving it as toggle button 
     getActionBar().setDisplayHomeAsUpEnabled(true); 
     getActionBar().setHomeButtonEnabled(true); 
     getActionBar().setBackgroundDrawable(
       new ColorDrawable(Color.parseColor("#009933"))); 
     //getActionBar().setIcon(
       // new ColorDrawable(getResources().getColor(android.R.color.transparent))); 
     mDrawerToggle = new ActionBarDrawerToggle(this, mDrawerLayout, 
       R.drawable.ic_drawer, //nav menu toggle icon 
       R.string.app_name, // nav drawer open - description for accessibility 
       R.string.app_name // nav drawer close - description for accessibility 
     ) { 
      public void onDrawerClosed(View view) { 
       getActionBar().setTitle(mTitle); 
       // calling onPrepareOptionsMenu() to show action bar icons 
       invalidateOptionsMenu(); 
      } 

      public void onDrawerOpened(View drawerView) { 
       getActionBar().setTitle(mDrawerTitle); 
       // calling onPrepareOptionsMenu() to hide action bar icons 
       invalidateOptionsMenu(); 
      } 
     }; 
     mDrawerLayout.setDrawerListener(mDrawerToggle); 

     if (savedInstanceState == null) { 
      // on first time display view for first nav item 
      displayView(0); 
     } 
    } 

    /** 
    * Slide menu item click listener 
    * */ 
    private class SlideMenuClickListener implements 
      ListView.OnItemClickListener { 
     @Override 
     public void onItemClick(AdapterView<?> parent, View view, int position, 
       long id) { 
      // display view for selected nav drawer item 
      displayView(position); 
     } 
    } 

    @Override 
    public boolean onCreateOptionsMenu(Menu menu) { 
     getMenuInflater().inflate(R.menu.main, menu); 
     return true; 
    } 

    @Override 
    public boolean onOptionsItemSelected(MenuItem item) { 
     // toggle nav drawer on selecting action bar app icon/title 
     if (mDrawerToggle.onOptionsItemSelected(item)) { 
      return true; 
     } 
     // Handle action bar actions click 
     switch (item.getItemId()) { 
     case R.id.action_settings: 
      return true; 
     default: 
      return super.onOptionsItemSelected(item); 
     } 
    } 

    /* * 
    * Called when invalidateOptionsMenu() is triggered 
    */ 
    @Override 
    public boolean onPrepareOptionsMenu(Menu menu) { 
     // if nav drawer is opened, hide the action items 
     boolean drawerOpen = mDrawerLayout.isDrawerOpen(mDrawerList); 
     menu.findItem(R.id.action_settings).setVisible(!drawerOpen); 
     return super.onPrepareOptionsMenu(menu); 
    } 

    /** 
    * Diplaying fragment view for selected nav drawer list item 
    * */ 
    private void displayView(int position) { 
     // update the main content by replacing fragments 
     Fragment fragment = null; 
     switch (position) { 
     case 0: 
      fragment = new HomeFragment(this); 
      break; 
     case 1: 
      fragment = new FindPeopleFragment(); 
      break; 
     case 2: 
      fragment = new PhotosFragment(); 
      break; 
     case 3: 
      fragment = new CommunityFragment(); 
      break; 
     case 4: 
      fragment = new PagesFragment(); 
      break; 
     case 5: 
      fragment = new WhatsHotFragment(); 
      break; 

     default: 
      break; 
     } 

     if (fragment != null) { 
      FragmentManager fragmentManager = getFragmentManager(); 
      fragmentManager.beginTransaction() 
        .replace(R.id.frame_container, fragment).commit(); 

      // update selected item and title, then close the drawer 
      mDrawerList.setItemChecked(position, true); 
      mDrawerList.setSelection(position); 
      setTitle(navMenuTitles[position]); 
      mDrawerLayout.closeDrawer(mDrawerList); 
     } else { 
      // error in creating fragment 
      Log.e("MainActivity", "Error in creating fragment"); 
     } 
    } 

    @Override 
    public void setTitle(CharSequence title) { 
     mTitle = title; 
     getActionBar().setTitle(mTitle); 
    } 

    /** 
    * When using the ActionBarDrawerToggle, you must call it during 
    * onPostCreate() and onConfigurationChanged()... 
    */ 

    @Override 
    protected void onPostCreate(Bundle savedInstanceState) { 
     super.onPostCreate(savedInstanceState); 
     // Sync the toggle state after onRestoreInstanceState has occurred. 
     mDrawerToggle.syncState(); 
    } 

    @Override 
    public void onConfigurationChanged(Configuration newConfig) { 
     super.onConfigurationChanged(newConfig); 
     // Pass any configuration change to the drawer toggls 
     mDrawerToggle.onConfigurationChanged(newConfig); 
    } 

} 

это мой фрагмент:

public class HomeFragment extends ListFragment { 

    private static final String TAG = MainActivity.class.getSimpleName(); 
    private Activity activity; 
    // Movies json url 
    private static final String url = "http://api.androidhive.info/json/movies.json"; 
    private ProgressDialog pDialog; 
    private List<Movie> movieList = new ArrayList<Movie>(); 
    private ListView listView; 
    private CustomListAdapter adapter; 
    public View rootView; 

    @SuppressLint("NewApi") 
    public HomeFragment(Activity acticity){ 

     this.activity=activity; 
    } 


    @Override 
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { 

     rootView = inflater.inflate(R.layout.listmain, container, false); 
     listView = (ListView) rootView.findViewById(R.id.list); 
     adapter = new CustomListAdapter(getActivity(), movieList); 
     listView.setAdapter(adapter); 

     pDialog = new ProgressDialog(getActivity()); 
     // Showing progress dialog before making http request 
     pDialog.setMessage("Loading..."); 
     pDialog.show(); 

     // changing action bar color 


     // Creating volley request obj 
     JsonArrayRequest movieReq = new JsonArrayRequest(url, new Response.Listener<JSONArray>() { 

      @Override 
      public void onResponse(JSONArray response) { 

       Log.d(TAG, response.toString()); 
       hidePDialog(); 

       // Parsing json 
       for (int i = 0; i < response.length(); i++) { 

        try { 

         JSONObject obj = response.getJSONObject(i); 
         Movie movie = new Movie(); 
         movie.setTitle(obj.getString("title")); 
         movie.setThumbnailUrl(obj.getString("image")); 
         movie.setRating(((Number) obj.get("rating")).doubleValue()); 
         movie.setYear(obj.getInt("releaseYear")); 

         // Genre is json array 
         JSONArray genreArry = obj.getJSONArray("genre"); 
         ArrayList<String> genre = new ArrayList<String>(); 
         for (int j = 0; j < genreArry.length(); j++) { 

          genre.add((String) genreArry.get(j)); 
         } 
         movie.setGenre(genre); 

         // adding movie to movies array 
         movieList.add(movie); 

        } catch (JSONException e) { 

         e.printStackTrace(); 
        } 
       } 

       // notifying list adapter about data changes 
       // so that it renders the list view with updated data 
       adapter.notifyDataSetChanged(); 
      } 
     }, new Response.ErrorListener() { 

      @Override 
      public void onErrorResponse(VolleyError error) { 

       VolleyLog.d(TAG, "Error: " + error.getMessage()); 
       hidePDialog(); 

      } 
     }); 

     // Adding request to request queue 
     AppController.getInstance().addToRequestQueue(movieReq); 
     return rootView; 
    } 

    @Override 
    public void onActivityCreated(Bundle savedInstanceState) {} 

    @Override 
    public void onDestroy() { 

     super.onDestroy(); 
     hidePDialog(); 
    } 

    private void hidePDialog() { 

     if (pDialog != null) { 

      pDialog.dismiss(); 
      pDialog = null; 
     } 
    } 
} 

и это мой customadapter:

public class CustomListAdapter extends BaseAdapter { 

    private Activity activity; 
    //public Context context; 
    private LayoutInflater inflater; 
    private List<Movie> movieItems; 
    ImageLoader imageLoader = AppController.getInstance().getImageLoader(); 

    public CustomListAdapter(Activity activity, List<Movie> movieItems) { 

     this.activity = activity; 
     this.movieItems = movieItems; 
     //this.context = context; 
    } 

    @Override 
    public int getCount() { 

     return movieItems.size(); 
    } 

    @Override 
    public Object getItem(int location) { 

     return movieItems.get(location); 
    } 

    @Override 
    public long getItemId(int position) { 

     return position; 
    } 

    @SuppressLint("InflateParams") 
    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 

     if (inflater == null) 
      inflater = (LayoutInflater) activity.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
     if (convertView == null) 
      convertView = inflater.inflate(R.layout.list_row, null); 

     if (imageLoader == null) 
      imageLoader = AppController.getInstance().getImageLoader(); 
     NetworkImageView thumbNail = (NetworkImageView) convertView.findViewById(R.id.thumbnail); 
     TextView title = (TextView) convertView.findViewById(R.id.title); 
     TextView rating = (TextView) convertView.findViewById(R.id.rating); 
     TextView genre = (TextView) convertView.findViewById(R.id.genre); 
     TextView year = (TextView) convertView.findViewById(R.id.releaseYear); 

     // getting movie data for the row 
     Movie m = movieItems.get(position); 

     // thumbnail image 
     thumbNail.setImageUrl(m.getThumbnailUrl(), imageLoader); 

     // title 
     title.setText(m.getTitle()); 

     // rating 
     rating.setText("Rating: " + String.valueOf(m.getRating())); 

     // genre 
     String genreStr = ""; 
     for (String str : m.getGenre()) { 

      genreStr += str + ", "; 
     } 
     genreStr = genreStr.length() > 0 ? genreStr.substring(0, genreStr.length() - 2) : genreStr; 
     genre.setText(genreStr); 

     // release year 
     year.setText(String.valueOf(m.getYear())); 

     return convertView; 
    } 
} 

мой журнал:

---

11-25 06:41:20.813: W/dalvikvm(1135): threadid=1: thread exiting with uncaught exception (group=0xa4c18648) 
11-25 06:41:20.821: E/AndroidRuntime(1135): FATAL EXCEPTION: main 
11-25 06:41:20.821: E/AndroidRuntime(1135): java.lang.RuntimeException: Unable to start activity ComponentInfo{info.androidhive.slidingmenu/info.androidhive.slidingmenu.MainActivity}: java.lang.NullPointerException 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2211) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2261) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread.access$600(ActivityThread.java:141) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1256) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.os.Handler.dispatchMessage(Handler.java:99) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.os.Looper.loop(Looper.java:137) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread.main(ActivityThread.java:5103) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at java.lang.reflect.Method.invoke(Method.java:525) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:737) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at dalvik.system.NativeStart.main(Native Method) 
11-25 06:41:20.821: E/AndroidRuntime(1135): Caused by: java.lang.NullPointerException 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at info.androidhive.slidingmenu.listadapter.CustomListAdapter.<init>(CustomListAdapter.java:28) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at info.androidhive.slidingmenu.HomeFragment.onCreateView(HomeFragment.java:57) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.Fragment.performCreateView(Fragment.java:1695) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:885) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1057) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.BackStackRecord.run(BackStackRecord.java:682) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1435) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.Activity.performStart(Activity.java:5142) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2184) 
11-25 06:41:20.821: E/AndroidRuntime(1135):  ... 11 more 

Answer 1

вы звоните customListAdapter, прежде чем ваша обработка JSON произошло. Таким образом, движитель, которому вы перешли в customListAdapter, не имеет никакого значения. Вот почему вы получаете исключение нулевого указателя.

Решение: Выполнить эту строку кода после обработки JSON завершения

listView.setAdapter (адаптер);

Лучший способ делать то, что вы пытаетесь это использовать AsyncTask для извлечения данных из сервера, и в методе onPostExecute из AsyncTask, вы выполняете линию

listView.setAdapter (адаптер);

Answer 2

Изначально ваш movieList имеет значение null. Данных нет.

adapter = new CustomListAdapter(getActivity(), movieList); 
listView.setAdapter(adapter); 

вам просто нужно, чтобы переместить код выше в onResponse() методы, а не onCreateView() метода. Таким образом, он выглядит как

 @Override 
     public void onResponse(JSONArray response) {..... 
      adapter = new CustomListAdapter(getActivity(), movieList); 
      listView.setAdapter(adapter); 
      adapter.notifyDataSetChanged(); 
     }....... 

В этом методе будут обновлены ваши данные и пользовательский интерфейс.