NullPointerException: Attempt to invoke virtual method AlertDialog.setTitle(java.lang.CharSequence) on a null object reference

Question

Here is the error:

04-01 10:37:47.077 2310-2326/zonup.asyc D/Create Response﹕ {"success":"false","msg":"Please enter email!!!"} 04-01 10:37:47.084
2310-2310/zonup.asyc D/AndroidRuntime﹕ Shutting down VM 04-01 10:37:47.084 2310-2310/zonup.asyc E/AndroidRuntime﹕ FATAL EXCEPTION: main Process: zonup.asyc, PID: 2310 java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.AlertDialog.setTitle(java.lang.CharSequence)' on a null object reference at zonup.asyc.MainActivity$SignmeUp.onPostExecute(MainActivity.java:122) at zonup.asyc.MainActivity$SignmeUp.onPostExecute(MainActivity.java:70) at android.os.AsyncTask.finish(AsyncTask.java:632) at android.os.AsyncTask.access$600(AsyncTask.java:177) at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5221) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:899) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:694)

public class MainActivity extends ActionBarActivity {

protected String stmail;
protected EditText editText;
protected Button button;
AlertDialog alertDialog;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    editText=(EditText) findViewById(R.id.editText);
    stmail=editText.getText().toString();
    button=(Button) findViewById(R.id.button);
    button.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            new SignmeUp().execute();
        }
    });
}


@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
class SignmeUp extends AsyncTask<String, String, String> {

    private ProgressDialog pDialog;
    JSONParser jsonParser = new JSONParser();

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        runOnUiThread(new Runnable() {
            @Override
            public void run() {
                pDialog = new ProgressDialog(MainActivity.this);
                pDialog.setMessage("Thanks for your Sign up...");
                pDialog.setIndeterminate(false);
                pDialog.setCancelable(true);
            }
        });
    }

    @Override
    protected String doInBackground(String... arg0) {
        // TODO Auto-generated method stub

        // Building Parameters
        List<NameValuePair> params = new ArrayList<NameValuePair>();
        params.add(new BasicNameValuePair("email", stmail));



        // getting JSON Object
        // Note that create product url accepts POST method
        JSONObject json = jsonParser.makeHttpRequest("http://api.php","GET", params);

        // check log cat fro response
        Log.d("Create Response", json.toString());

        // check for success tag
        try {
            String success = json.getString("success");

            if (stmail != null & success == "true") {
                Toast.makeText(MainActivity.this, "Youre Email Posted..", Toast.LENGTH_SHORT).show();
            } else {

            }
        } catch (JSONException e) {
            e.printStackTrace();
        }

        return null;
    }

    @SuppressWarnings("deprecation")
    protected void onPostExecute(String file_url) {
        // dismiss the dialog once done

        editText.setText("");
        alertDialog.setTitle("Info");

        alertDialog.setMessage("You have been subscribed o the ");
        alertDialog.setButton("OK", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int which) {
                // here you can add functions

            }
        });

        alertDialog.show();

    }

}
}

Put AlertDialog.Builder alertDialog = new AlertDialog.Builder(MainActivity.this); above alertDialog.setTitle("Info"); line — Dhaval Patel, Apr 01 '15 at 05:24

score 1 · Answer 1 · answered Apr 01 '15 at 06:08

1

You have a null pointer exception on dialog.setTitle("Info") but it appears you really should be calling pDialog.setTitle("Info") since the dialog you initialized in onPreExecute is pDialog rather than alertDialog

answered Apr 01 '15 at 06:08

Tanner Perrien

3,133
1
28
35

score 1 · Answer 2 · answered Jul 13 '16 at 05:09

You Try Codeing you

you try in method onPreExecute

  private ProgressDialog PD; 

        if(PD == null){

    //
                        PD = new ProgressDialog(SplashScreenActivity.this);
                        PD.setMessage("Please Wait..");
                        PD.setIndeterminate(false);
                        PD.setCancelable(true);
                        PD.show();
                }

and you cloce PrpgressDialog in method onPostExecute

if(PD.isShowing()){
                    PD.dismiss();
                    goNext();
                }

score 0 · Accepted Answer · answered Apr 01 '15 at 05:59

Rather using AlertDialog use AlertDialog.Builder. As AlertDialog is deprected. Also you need to show progressdialog too.

 @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pDialog = new ProgressDialog(MainActivity.this);
        pDialog.setMessage("Thanks for your Sign up...");
        pDialog.setIndeterminate(false);
        pDialog.setCancelable(true);
        pDialog.show();
    }

In onPostExecute method dismiss the progressbar. Also Use AlertDialog.Builder.

 protected void onPostExecute(String file_url) {
        // dismiss the dialog once done

     if(pDialog.isShowing()){
       pDialog.dismiss();
      }
        editText.setText("");
      AlertDailog.Builder builder = new AlertDialog.Builder(Activity.this);
             builder.setText("");
             builder.setMessege("");
             builder.create().show();
        });

NullPointerException: Attempt to invoke virtual method AlertDialog.setTitle(java.lang.CharSequence) on a null object reference

3 Answers3