private void loginUser(){
        final String username = mUsernameView.getText().toString().trim();
        final String password = mPasswordView.getText().toString().trim();

        StringRequest stringRequest = new StringRequest(Request.Method.POST, URLS.POST_LOGIN,
                new Response.Listener<String>() {
                    @Override
                    public void onResponse(String response) {
                        try {
                            JSONObject jsonObject = new JSONObject(response);
                            if(jsonObject.has("key")){
                                SharedPreferences.Editor prefEditor = sharedPref.edit();
                                prefEditor.putString(SharedPreference.Account.AUTH_TOKEN, jsonObject.optString("key"));
                                prefEditor.apply();
                                Toast.makeText(LoginActivity.this,
                                        "Logging In",Toast.LENGTH_SHORT).show();
                                nextActivity(false);
                                setReturn(true);
                            }else{
                                Toast.makeText(LoginActivity.this,
                                        "Invalid Credentials",Toast.LENGTH_SHORT).show();
                                setReturn(false);
                            }
                        } catch (JSONException e) {
                            Toast.makeText(LoginActivity.this,
                                    "Invalid Credentials",Toast.LENGTH_SHORT).show();
                            setReturn(false);
                        }
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {
                        Toast.makeText(LoginActivity.this,
                                "Invalid Credentials",Toast.LENGTH_SHORT).show();
                        setReturn(false);
                    }
                }){
            @Override
            protected Map<String,String> getParams(){
                Map<String,String> params = new HashMap<>();
                params.put(SharedPreference.Account.USERNAME, username);
                params.put(SharedPreference.Account.PASSWORD,password);
                return params;
            }

        };

        RequestQueue requestQueue = Volley.newRequestQueue(this);
        requestQueue.add(stringRequest);
    }