JsonArrayRequest抛出空指针异常

Question

当我按下我的登录按钮java.lang.NullPointerException发生时，它假设有数据从数据库中检索并放入我在代码中定义的数组列表中。任何人都有想法如何解决这个问题？在此先感谢：d

package info.androidhive.materialdesign.activity; 
import android.app.ProgressDialog; 
import android.content.Context; 
import android.net.ConnectivityManager; 
import android.net.NetworkInfo; 
import android.support.v4.app.Fragment; 
import android.os.Bundle; 
import android.view.LayoutInflater; 
import android.view.View; 
import android.view.ViewGroup; 
import android.widget.Button; 
import android.widget.EditText; 
import android.widget.TextView; 
import android.widget.Toast; 
import com.android.volley.RequestQueue; 
import com.android.volley.Response; 
import com.android.volley.VolleyError; 
import com.android.volley.toolbox.JsonArrayRequest; 
import com.android.volley.toolbox.Volley; 

import org.json.JSONArray; 
import org.json.JSONException; 
import org.json.JSONObject; 

import java.util.List; 

import info.androidhive.materialdesign.R; 

    enter code here 

public class loginFragment extends Fragment { 
    private TextView textViewForgotPass, textView2; 
    private Button btnLogin; 
    private EditText editTextEmail, editTextPassword; 
    List<UserAccount> uaList; 
    private ProgressDialog pDialog; 
    private Context context; 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 

    } 


    public View onCreateView(LayoutInflater inflater, ViewGroup container, 
          Bundle savedInstanceState) { 
     View rootView = inflater.inflate(R.layout.fragment_login, container, false); 
     textViewForgotPass= (TextView)rootView.findViewById(R.id.textViewForgotPass); 
     textViewForgotPass.setTextColor(0xAA81DEFD); 
     editTextEmail = (EditText)rootView.findViewById(R.id.editTextEmail); 
     editTextPassword = (EditText)rootView.findViewById(R.id.editTextPassword); 
     btnLogin=(Button)rootView.findViewById(R.id.buttonLogin); 
     btnLogin.setOnClickListener(loginListener); 
     textViewForgotPass.setOnClickListener(forgotPassListener); 
     pDialog = new ProgressDialog(loginFragment.this.getContext()); 
     textView2=(TextView)rootView.findViewById(R.id.textView2); 
     return rootView; 
    } 

    View.OnClickListener loginListener = new View.OnClickListener() { 
     @Override 
     public void onClick(final View v) { 
      readUser(); 

     } 
    }; 

    View.OnClickListener forgotPassListener = new View.OnClickListener() { 
     @Override 
     public void onClick(final View v) { 
      Toast.makeText(loginFragment.this.getContext(), "Forgot Password?", Toast.LENGTH_SHORT).show(); 
     } 
    }; 

    private void readUser() { 
     try { 
      // Check availability of network connection. 
      ConnectivityManager connMgr = (ConnectivityManager)getActivity().getSystemService(Context.CONNECTIVITY_SERVICE); 
      NetworkInfo networkInfo = connMgr.getActiveNetworkInfo(); 
      Boolean isConnected = networkInfo != null && networkInfo.isConnectedOrConnecting(); 
      if (isConnected) { 
       //downloadUser().execute(getResources().getString(R.string.get_user_url)); 
       downloadUser(this.getActivity(), getResources().getString(R.string.get_user_url)); 
      } else { 
       Toast.makeText(loginFragment.this.getContext(), "Network is NOT available", 
         Toast.LENGTH_SHORT).show(); 
      } 
     } catch (Exception e) { 
      Toast.makeText(loginFragment.this.getContext(), 
        "Error reading record:" + e.getMessage(), 
        Toast.LENGTH_SHORT).show(); 
     } 
    } 

    private void downloadUser(Context context, String url) { 
     //mPostCommentResponse.requestStarted(); 
     RequestQueue queue = Volley.newRequestQueue(context); 

     JsonArrayRequest jsonObjectRequest = new JsonArrayRequest(url, 
       new Response.Listener<JSONArray>() { 
        @Override 
        public void onResponse(JSONArray response) { 
         if (!pDialog.isShowing()) 
          pDialog.show(); 

         try{ 
          //Clear list 
          uaList.clear(); 

          for(int i=0; i < response.length();i++){ 
           JSONObject userAccResponse = (JSONObject) response.get(i); 
           String email = userAccResponse.getString("email"); 
           String password = userAccResponse.getString("password"); 
           String name = userAccResponse.getString("name"); 
           String address = userAccResponse.getString("address"); 
           String phonenum = userAccResponse.getString("phonenum"); 
           UserAccount user = new UserAccount(); 
           user.setEmail(email); 
           user.setPassword(password); 
           user.setName(name); 
           user.setAddress(address); 
           user.setPhoneNum(phonenum); 
           uaList.add(user); 
           textView2.setText(uaList.get(0).getEmail()); 
          } 

          if (pDialog.isShowing()) 
           pDialog.dismiss(); 

         }catch (JSONException e){ 
          Toast.makeText(loginFragment.this.getContext(), "Erroraaaa:" + e.getMessage(), Toast.LENGTH_SHORT).show(); 
         } 
        } 
       }, 
       new Response.ErrorListener() { 
        @Override 
        public void onErrorResponse(VolleyError volleyError) { 
         Toast.makeText(loginFragment.this.getContext(), "Errorssss:" + volleyError.getMessage(), Toast.LENGTH_SHORT).show(); 
         if (pDialog.isShowing()) 
          pDialog.dismiss(); 
        } 
       }); 
     queue.add(jsonObjectRequest); 
    } 



} 

这是错误日志

12-15 18:38:01.618 12060-12060/? E/AndroidRuntime﹕ FATAL EXCEPTION: main 
    java.lang.NullPointerException 
      at info.androidhive.materialdesign.activity.loginFragment$3.onResponse(loginFragment.java:107) 
      at info.androidhive.materialdesign.activity.loginFragment$3.onResponse(loginFragment.java:99) 
      at com.android.volley.toolbox.JsonRequest.deliverResponse(JsonRequest.java:65) 
      at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:99) 
      at android.os.Handler.handleCallback(Handler.java:605) 
      at android.os.Handler.dispatchMessage(Handler.java:92) 
      at android.os.Looper.loop(Looper.java:154) 
      at android.app.ActivityThread.main(ActivityThread.java:4624) 
      at java.lang.reflect.Method.invokeNative(Native Method) 
      at java.lang.reflect.Method.invoke(Method.java:511) 
      at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:809) 
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:576) 
      at dalvik.system.NativeStart.main(Native Method) 

Answer 1

你uaList为空和你试图将其清除。

与uaList = new Arraylist<>();