检索解析用户列表android

Question

因此，我试图从所有解析用户获取用户名列表，并将其显示在列表视图中，这样我就可以在我的应用程序中搜索任何人，但我得到这个错误，而不是：

E/AndroidRuntime: FATAL EXCEPTION: main 
       Process: com.les20162.room8, PID: 19957 
       java.lang.NullPointerException: storage == null 
        at java.util.Arrays$ArrayList.<init>(Arrays.java:38) 
        at java.util.Arrays.asList(Arrays.java:155) 
        at com.les20162.room8.Activities.RoomatesFragment.initList(RoomatesFragment.java:171) 
        at com.les20162.room8.Activities.RoomatesFragment.onCreateView(RoomatesFragment.java:81) 
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:2189) 
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1299) 
        at android.support.v4.app.FragmentManagerImpl.moveFragmentToExpectedState(FragmentManager.java:1528) 
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1595) 
        at android.support.v4.app.BackStackRecord.executeOps(BackStackRecord.java:757) 
        at android.support.v4.app.FragmentManagerImpl.executeOps(FragmentManager.java:2355) 
        at android.support.v4.app.FragmentManagerImpl.executeOpsTogether(FragmentManager.java:2146) 
        at android.support.v4.app.FragmentManagerImpl.optimizeAndExecuteOps(FragmentManager.java:2098) 
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:2008) 
        at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:710) 
        at android.os.Handler.handleCallback(Handler.java:739) 
        at android.os.Handler.dispatchMessage(Handler.java:95) 
        at android.os.Looper.loop(Looper.java:148) 
        at android.app.ActivityThread.main(ActivityThread.java:7409) 
        at java.lang.reflect.Method.invoke(Native Method) 
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1230) 
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1120) 

这是我用得到的用户列表的代码：

public class RoomatesFragment extends Fragment { 

//variables 
private EditText    search; 
private String[]    users; 
private ArrayList<String> listUsers; 
private ArrayAdapter<String> adapter; 
private ListView    listView; 

private OnFragmentInteractionListener mListener; 

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

public static RoomatesFragment newInstance(String param1, String param2) { 
    RoomatesFragment fragment = new RoomatesFragment(); 
    Bundle args = new Bundle(); 
    return fragment; 
} 

@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 
    final View myView; 
    myView = inflater.inflate(R.layout.fragment_roomates, container, false); 

    listView = (ListView) myView.findViewById(R.id.listviewMoradores); 
    search = (EditText) myView.findViewById(R.id.search); 

    initList(); 

    search.addTextChangedListener(new TextWatcher() { 
     @Override 
     public void beforeTextChanged(CharSequence charSequence, int i, int i1, int i2) { 

     } 

     @Override 
     public void onTextChanged(CharSequence charSequence, int i, int i1, int i2) { 
      if(charSequence.toString().equals("")){ 
       initList(); 
      } 
      else{ 
       searchUser(charSequence.toString()); 
      } 
     } 

     @Override 
     public void afterTextChanged(Editable editable) { 

     } 
    }); 

    return myView; 
} 

public void searchUser(String userToSearch) { 
    for(String user: users){ 
     if(!user.contains(userToSearch)){ 
      listUsers.remove(user); 
     } 
    } 

    adapter.notifyDataSetChanged(); 
} 

// TODO: Rename method, update argument and hook method into UI event 
public void onButtonPressed(Uri uri) { 
    if (mListener != null) { 
     mListener.onFragmentInteraction(uri); 
    } 
} 

@Override 
public void onAttach(Context context) { 
    super.onAttach(context); 
    if (context instanceof OnFragmentInteractionListener) { 
     mListener = (OnFragmentInteractionListener) context; 
    } else { 
     throw new RuntimeException(context.toString() 
       + " must implement OnFragmentInteractionListener"); 
    } 
} 

@Override 
public void onDetach() { 
    super.onDetach(); 
    mListener = null; 
} 

public interface OnFragmentInteractionListener { 
    // TODO: Update argument type and name 
    void onFragmentInteraction(Uri uri); 
} 

private void initList(){ 
    ParseQuery<ParseUser> query = ParseUser.getQuery(); 
    query.findInBackground(new FindCallback<ParseUser>() { 
     public void done(List<ParseUser> objects, ParseException e) { 
      users = new String[objects.size()+1]; 
      if (e == null) { 
       for (int i = 0; i < objects.size(); i++) { 
        users[i] = objects.get(i).getUsername(); 
       } 
      } else { 
       users[0] = "NONE"; 
      } 
     } 
    }); 
    listUsers = new ArrayList<>(Arrays.asList(users)); 
    adapter = new ArrayAdapter<String>(getActivity(), R.layout.list_item, R.id.user, listUsers); 

    listView.setAdapter(adapter); 
} 

}

我tryed几乎所有的东西，但我不断收到同样的错误，你们有没有任何意见至于如何纠正这一点？我很新的android编程，所以，任何帮助将欢迎:)

P.S：英语不是我的母语，所以很抱歉有任何错误。

Answer 1

可能试着使用AsyncTask。你可以获取列表，一旦完成，尝试绘制。列表可能没有填充列表并试图绘制它。