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  • Null Pointer Exception Error in Android App

    @programmer.deenwebindia
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    I have faced a problem, when I clicked on login button on login activity. Below is my debug logact mentioned: 

     

    04-15 15:07:45.924 2533-2533/volleyjson.androidhive.info.myapplication E/AndroidRuntime: FATAL EXCEPTION: main
                                                                                             Process: volleyjson.androidhive.info.myapplication, PID: 2533
                                                                                             java.lang.NullPointerException: Attempt to invoke virtual method 'boolean

     

    android.app.ProgressDialog.isShowing()' on a null object reference
                                                                                                 at volleyjson.androidhive.info.myapplication.login.showProgressDialog(login.java:55)
                                                                                                 at volleyjson.androidhive.info.myapplication.login.makeJsonObjReq(login.java:64)
                                                                                                 at volleyjson.androidhive.info.myapplication.login.onClick(login.java:120)
                                                                                                 at android.view.View.performClick(View.java:5637)
                                                                                                 at android.view.View$PerformClick.run(View.java:22429)
                                                                                                 at android.os.Handler.handleCallback(Handler.java:751)
                                                                                                 at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                                 at android.os.Looper.loop(Looper.java:154)
                                                                                                 at android.app.ActivityThread.main(ActivityThread.java:6119)
                                                                                                 at java.lang.reflect.Method.invoke(Native Method)
                                                                                                 at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886)
                                                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776)


    And this is my login.java:

     

    1. package volleyjson.androidhive.info.myapplication;
    2.  
    3. import android.app.Activity;
    4. import android.app.ProgressDialog;
    5. import android.content.Intent;
    6. import android.os.Bundle;
    7. import android.util.Log;
    8. import android.view.View;
    9. import android.widget.Button;
    10. import android.widget.EditText;
    11. import android.widget.TextView;
    12.  
    13. import com.android.volley.AuthFailureError;
    14. import com.android.volley.Request;
    15. import com.android.volley.Response;
    16. import com.android.volley.VolleyError;
    17. import com.android.volley.VolleyLog;
    18. import com.android.volley.toolbox.JsonObjectRequest;
    19. import volleyjson.androidhive.info.myapplication.app.AppController;
    20.  
    21. import org.json.JSONObject;
    22.  
    23. import java.util.HashMap;
    24. import java.util.Map;
    25.  
    26. @SuppressWarnings("ALL")
    27. public class login extends Activity implements View.OnClickListener{
    28.     private final String TAG =  login.class.getSimpleName();
    29.     private static final String LOGIN_URL = "http://www.nishkarsh.co.in/api/login";
    30.     private static final String KEY_EMAIL = "email";
    31.     private ProgressDialog pDialog;
    32.     private TextView t1;
    33.     private TextView t2;
    34.     private TextView t3;
    35.     private EditText ed1;
    36.     private Button b1;
    37.     private String email;
    38.  
    39.  
    40.     @Override
    41.     protected void onCreate(Bundle savedInstanceState) {
    42.         super.onCreate(savedInstanceState);
    43.         setContentView(R.layout.login_dialogue);
    44.         t1 = (TextView) findViewById(R.id.textView1);
    45.         t2 = (TextView) findViewById(R.id.textView2);
    46.         t3 = (TextView) findViewById(R.id.textView3);
    47.         ed1 = (EditText) findViewById(R.id.RegEmail);
    48.         b1 = (Button) findViewById(R.id.btnLogin);
    49.         b1.setOnClickListener(this);
    50.         ProgressDialog pDialog = new ProgressDialog(this);
    51.         pDialog.setMessage("Loading...");
    52.         pDialog.setCancelable(false);
    53.     }
    54.     private void showProgressDialog() {
    55.         if (!pDialog.isShowing())
    56.             pDialog.show();
    57.     }
    58.  
    59.     private void hideProgressDialog() {
    60.         if (pDialog.isShowing())
    61.             pDialog.hide();
    62.     }
    63.     private void makeJsonObjReq() {
    64.         showProgressDialog();
    65.         JsonObjectRequest jsonObjReq = new JsonObjectRequest(Request.Method.POST,
    66.                 LOGIN_URL , null,
    67.                 new Response.Listener<JSONObject>() {
    68.  
    69.                     @Override
    70.                     public void onResponse(JSONObject response) {
    71.                         Log.d(TAG, response.toString());
    72.                         openProfile();
    73.                         pDialog.hide();
    74.                     }
    75.                 }, new Response.ErrorListener() {
    76.  
    77.             @Override
    78.             public void onErrorResponse(VolleyError error) {
    79.                 VolleyLog.d(TAG, "Error: " + error.getMessage());
    80.                 hideProgressDialog();
    81.             }
    82.         }) {
    83.  
    84.             /**
    85.              * Passing some request headers
    86.              * */
    87.             @Override
    88.             public Map<String, String> getHeaders() throws AuthFailureError {
    89.                 HashMap<String, String> headers = new HashMap<>();
    90.                 headers.put("Content-Type", "application/json");
    91.                 return headers;
    92.             }
    93.             @Override
    94.             protected Map<String, String> getParams() {
    95.                 Map<String, String> params = new HashMap<>();
    96.                 params.put(KEY_EMAIL, email);
    97.  
    98.                 return params;
    99.             }
    100.  
    101.         };
    102.  
    103.         // Adding request to request queue
    104.         String tag_json_obj = "jsonObjReq ";
    105.         AppController.getInstance().addToRequestQueue(jsonObjReq,
    106.                 tag_json_obj);
    107.  
    108.         // Cancelling request
    109.         // ApplicationController.getInstance().getRequestQueue().cancelAll(tag_json_obj);
    110.     }
    111.     private void openProfile(){
    112.         Intent intent = new Intent(login.this, MainActivity.class);
    113.         intent.putExtra(KEY_EMAIL,email);
    114.         startActivity(intent);
    115.     }
    116.  
    117.     @Override
    118.     public void onClick(View v) {
    119.  
    120.         makeJsonObjReq();
    121.     }
    122. }
    Android Runtime Permission
    Answer it

 4 Answer(s)

  • @Ataimo7
    Recommendations Offline Message

    over 6 years ago

    I agree with @programmer

    ProgressDialog pDialog = new ProgressDialog(this);
    pDialog.setMessage("Loading...");
    pDialog.setCancelable(false);

    Re declaring pDialog has a local variable, overshadows the instance variable and prevents it from being initialized. Therefore the solution his to just initialize it.  

    pDialog = new ProgressDialog(this);
    pDialog.setMessage("Loading...");
    pDialog.setCancelable(false);
  • @programmer.deenwebindia
    Recommendations Offline Message

    almost 8 years ago

    Change

    b1.setOnClickListener(this); 
ProgressDialog pDialog = new ProgressDialog(this); 
pDialog.setMessage("Loading...");

    to

    b1.setOnClickListener(this); 
pDialog = new ProgressDialog(this); 
pDialog.setMessage("Loading...");

    pDialog must be class member, in you case you shadow it with a local variable. 
    image

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