View not attached to window manager and app crash

Question

m.example.arihant.pludoc E/AndroidRuntime: FATAL EXCEPTION: main
  Process: com.example.arihant.pludoc, PID: 9852
  java.lang.IllegalArgumentException: View=com.android.internal.policy.impl.PhoneWindow$DecorView{2ed82f1e V.E..... R......D 0,0-1026,348} not attached to window manager
      at android.view.WindowManagerGlobal.findViewLocked(WindowManagerGlobal.java:396)
      at android.view.WindowManagerGlobal.removeView(WindowManagerGlobal.java:322)
      at android.view.WindowManagerImpl.removeViewImmediate(WindowManagerImpl.java:116)
      at android.app.Dialog.dismissDialog(Dialog.java:341)
      at android.app.Dialog.dismiss(Dialog.java:324)
      at com.example.arihant.pludoc.Login.hideDialog(Login.java:213)
      at com.example.arihant.pludoc.Login.access$400(Login.java:42)
      at com.example.arihant.pludoc.Login$5.onErrorResponse(Login.java:186)
      at com.android.volley.Request.deliverError(Request.java:524)
      at com.android.volley.ExecutorDelivery$ResponseDeliveryRunnable.run(ExecutorDelivery.java:101)
      at android.os.Handler.handleCallback(Handler.java:739)
      at android.os.Handler.dispatchMessage(Handler.java:95)
      at android.os.Looper.loop(Looper.java:135)
      at android.app.ActivityThread.main(ActivityThread.java:5300)
      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:904)
      at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:699)
02-01 00:01:25.547 9852-9852/com.example.arihant.pludoc D/AppTracker: App Event: crash

CODE:

public class Login extends AppCompatActivity  {

    private static final String[] DUMMY_CREDENTIALS = new String[]{
            "foo@example.com:hello", "bar@example.com:world"
    };
    private static final String TAG ="" ;

    private UserLoginTask mAuthTask = null;
    private EditText mPasswordView;
    private View mProgressView;
    private View mLoginFormView;
    private EditText mPhoneView;
    private TextView mForgotPass;
    private SessionManager session;
    private SQLiteHandler db;
    private ProgressDialog pDialog;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.login);
        setupActionBar();
        pDialog = new ProgressDialog(this);
        pDialog.setCancelable(false);
        db = new SQLiteHandler(getApplicationContext());
        session = new SessionManager(getApplicationContext());
        mPasswordView =(EditText)findViewById(R.id.password);
        mPhoneView = (EditText)findViewById(R.id.phone);
        mForgotPass = (TextView)findViewById(R.id.forgotpass);

        if (session.isLoggedIn()) {

            Intent intent = new Intent(Login.this, Mainpage.class);
            startActivity(intent);
            finish();
        }

        mForgotPass.setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View view) {

            }
        });

        Button mEmailSingUpButton = (Button)findViewById(R.id.sign_up_button);
        mEmailSingUpButton.setOnClickListener(new OnClickListener(){
            @Override
            public void onClick(View view) {
               Intent i1 = new Intent(Login.this,Signup.class);
                startActivity(i1);
            }
        });

        Button mEmailSignInButton = (Button) findViewById(R.id.sign_in_button);
        mEmailSignInButton.setOnClickListener(new OnClickListener() {
            @Override
            public void onClick(View view) {
                String phone = mPhoneView.getText().toString().trim();
                String password = mPasswordView.getText().toString().trim();

                if (!phone.isEmpty() && !password.isEmpty()) {
                    attemptLogin();
                    checkLogin(phone , password);
                } else {
                    Toast.makeText(getApplicationContext(),
                            "Please enter the credentials!", Toast.LENGTH_LONG)
                            .show();
                }
            }
        });

        mLoginFormView = findViewById(R.id.login_form);
        mProgressView = findViewById(R.id.login_progress);
    }

    private void checkLogin(final String phone, final String password) {
        // Tag used to cancel the request
        String tag_string_req = "req_login";

        pDialog.setMessage("Logging in ...");
        showDialog();


        StringRequest strReq = new StringRequest(Method.POST,
                AppConfig.URL_LOGIN, new Response.Listener<String>() {

            @Override
            public void onResponse(String response) {
                Log.d(TAG, "Login Response: " + response.toString());
                hideDialog();

                try {
                    JSONObject jObj = new JSONObject(response);
                    boolean error = jObj.getBoolean("error");


                    if (!error) {

                        session.setLogin(true);


                        String uid = jObj.getString("uid");

                        JSONObject user = jObj.getJSONObject("user");
                        String name = user.getString("name");
                        String email = user.getString("email");
                        String phone = user.getString("phone");
                        String created_at = user
                                .getString("created_at");


                        db.addUser(name,email, phone, uid, created_at);


                        Intent intent = new Intent(Login.this,
                                Mainpage.class);
                        startActivity(intent);
                        finish();
                    } else {

                        String errorMsg = jObj.getString("error_msg");
                        Toast.makeText(getApplicationContext(),
                                errorMsg, Toast.LENGTH_LONG).show();
                    }
                } catch (JSONException e) {

                    e.printStackTrace();
                    Toast.makeText(getApplicationContext(), "Json error: " + e.getMessage(), Toast.LENGTH_LONG).show();
                }

            }
        }, new Response.ErrorListener() {

            @Override
            public void onErrorResponse(VolleyError error) {
                Log.e(TAG, "Login Error: " + error.getMessage());
                Toast.makeText(getApplicationContext(),
                        error.getMessage(), Toast.LENGTH_LONG).show();
                hideDialog();
            }
        }) {

            @Override
            protected Map<String, String> getParams() {
                // Posting parameters to login url
                Map<String, String> params = new HashMap<String, String>();
                params.put("phone", phone);
                params.put("password", password);

                return params;
            }

        };

        // Adding request to request queue
        AppController.getInstance().addToRequestQueue(strReq, tag_string_req);
    }

    private void showDialog() {
        if (!pDialog.isShowing())
            pDialog.show();
    }

    private void hideDialog() {
        if (pDialog.isShowing())
            pDialog.dismiss();
    }



    @TargetApi(Build.VERSION_CODES.HONEYCOMB)
    private void setupActionBar() {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB) {
            // Show the Up button in the action bar.
            getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        }
    }


    private void attemptLogin() {
        if (mAuthTask != null) {
            return;
        }

        // Reset errors.
        mPhoneView.setError(null);
        mPasswordView.setError(null);



        String phone = mPhoneView.getText().toString();
        String password = mPasswordView.getText().toString();

        boolean cancel = false;
        View focusView = null;


        if (TextUtils.isEmpty(phone)) {
            mPhoneView.setError(getString(R.string.error_field_required));
            focusView = mPhoneView;
            cancel = true;
        } else if (isPhoneValid(phone)) {
            mPhoneView.setError(getString(R.string.error_invalid_phone));
            focusView = mPhoneView;
            cancel = true;
        }
        else if (TextUtils.isEmpty(password)) {
            mPasswordView.setError(getString(R.string.error_field_required));
            focusView = mPasswordView;
            cancel = true;
        }
        else if (!TextUtils.isEmpty(password) && !isPasswordValid(password)) {
            mPasswordView.setError(getString(R.string.error_invalid_password));
            focusView = mPasswordView;
            cancel = true;
        }




        if (cancel) {
            focusView.requestFocus();
        } else {
            showProgress(true);
            mAuthTask = new UserLoginTask(phone, password);
            mAuthTask.execute((Void) null);
        }
    }



    private boolean isPhoneValid(String phone){
        return phone.length()!=10;
    }
    private boolean isPasswordValid(String password) {
        return password.length() > 4;
    }

    @TargetApi(Build.VERSION_CODES.HONEYCOMB_MR2)
    private void showProgress(final boolean show) {
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.HONEYCOMB_MR2) {
            int shortAnimTime = getResources().getInteger(android.R.integer.config_shortAnimTime);

            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
            mLoginFormView.animate().setDuration(shortAnimTime).alpha(
                    show ? 0 : 1).setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
                }
            });

            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
            mProgressView.animate().setDuration(shortAnimTime).alpha(
                    show ? 1 : 0).setListener(new AnimatorListenerAdapter() {
                @Override
                public void onAnimationEnd(Animator animation) {
                    mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
                }
            });
        } else {
            mProgressView.setVisibility(show ? View.VISIBLE : View.GONE);
            mLoginFormView.setVisibility(show ? View.GONE : View.VISIBLE);
        }
    }



    public class UserLoginTask extends AsyncTask<Void, Void, Boolean> {

        private final String mPhone;

        private final String mPassword;

        UserLoginTask(String phone, String password) {
            mPhone = phone;
            mPassword = password;
        }

        @Override
        protected Boolean doInBackground(Void... params) {
            // TODO: attempt authentication against a network service.

            try {
                // Simulate network access.
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                return false;
            }

            for (String credential : DUMMY_CREDENTIALS) {
                String[] pieces = credential.split(":");
                if (pieces[0].equals(mPhone)) {
                    // Account exists, return true if the password matches.
                    return pieces[1].equals(mPassword);
                }
            }

            // TODO: register the new account here.
            return true;
        }

        @Override
        protected void onPostExecute(final Boolean success) {
            mAuthTask = null;
            showProgress(false);

            if (success) {
                finish();
            } else {
                mPasswordView.setError(getString(R.string.error_incorrect_password));
                mPasswordView.requestFocus();
            }
        }

        @Override
        protected void onCancelled() {
            mAuthTask = null;
            showProgress(false);
        }
    }
}