Question

I am developing android application which requires user to Login. This application relies on web server to verify the user details so that user can logged in. My problem starts here, there is no problem for logging in user, but when ever user press home button and goes back to the app, login screen is displayed which is very bad.

I have heard of SharedPrefrences but i don’t know how can i save user details using this, so that user can directly move to main activity.

I have included my source code here. If anybody familiar with SharedPrefrences can help me to solve this. Example with my cod will be helpful.

using System;

using Android.App;
using Android.Content;
using Android.Runtime;
using Android.Views;
using Android.Widget;
using Android.OS;
using Android.Locations;
using RestSharp;
using TheNorthStar.Api.Requests;
using TheNorthStar.Api.Results;
using NorthStar.Driver.Application;
using Android.Preferences;
using Object = Java.Lang.Object;


namespace NorthStar.Driver
{
    public class DriverLogonAsync : AsyncTask

    {
        private ProgressDialog processDialog;
        private Context m_context;
        private DriverLogon m_driver;

        private bool _resterror;

        public DriverLogonAsync( Context context, DriverLogon driver )
        {
            m_context = context;
            m_driver = driver;

            _resterror = false;
        }

        /*
         * throws
         * should separate out logic and use MyMessagebox..
         */
        private void SetComfirmAlertBox(string carNum, DriverLogonResult result)
        {
            var api = new ConnectToSever(Helper.GetServer(m_context));
            string resultOfCarDetail; CarDetails res;
            try
            {
                resultOfCarDetail = api.ComfirmLogginOn(m_driver);
            }
            catch
            {
                Android.Util.Log.Info("EXC_conflogon1", "confirm logging on failed");
                throw;
            }
            try
            {
                res = Newtonsoft.Json.JsonConvert.DeserializeObject<CarDetails>(resultOfCarDetail);
            }
            catch (Exception ex)
            {
                Android.Util.Log.Info("EXC_conflogon2", "deserialize confirm logging on failed\n" + ex.Message);
                throw;
            }

            if (res.carExists != true)
            {
                MyMessageBox.SetAlertBox("Opps!!!!!!!!", "This Car Number Was Wrong!!!!", "OK", m_context);
            }
            else
            {
                string carType = res.carType;
                string seatNum = res.numOfSeats.ToString();
               // MainActivity act = new MainActivity( result.driverId );
                var mact = new Intent(m_context,typeof(MainActivity) );
                mact.PutExtra( "driverID",  result.driverId.ToString() );
                MyMessageBox.SetAlertBox("Comfirm!", "Your car is a: " + carType + " with " + seatNum + " seats??", "Yes", "No", mact,m_context);


            }
        }

        /*private void ChangeDriverStatues()
        {

        }*/

        protected override void OnPreExecute()
        {
            base.OnPreExecute();
            processDialog = ProgressDialog.Show( m_context, "Driver Loging On...", "Please Wait...", true, true);
        }



        protected override Object DoInBackground(params Object[] @params)
        {
            var api = new ConnectToSever(Helper.GetServer(m_context));

            string res = string.Empty;
            try
            {
                res = api.DriverLogingOn(m_driver);
            }
            catch
            {
                _resterror = true;
                Android.Util.Log.Info("EXC_dlogon1", "driver logon failed");
                return -1;
            }
            return res;
        }

        protected override void OnPostExecute(Object result)
        {
            base.OnPostExecute(result);
            //hide and kill the progress dialog
            processDialog.Hide();
            processDialog.Cancel();

            if (_resterror == true)
            {
                Android.Util.Log.Info("EXC_dlogon2", "logon connection has failed, noop");
                return;
            }

            DriverLogonResult resDriverDetail;
            try
            {
                resDriverDetail = Newtonsoft.Json.JsonConvert.DeserializeObject<DriverLogonResult>(result.ToString());
            }
            catch (Exception ex)
            {
                Android.Util.Log.Info("EXC_dlogon3", "logon deser has failed, noop\n" + ex.Message);
                return;
            }

            if (resDriverDetail.logonSuccess)
            {
                this.SetComfirmAlertBox( m_driver.carNum, resDriverDetail );  
            }
            else
            {
                MyMessageBox.SetAlertBox("Wrong!", "Wrong username or password!!!", "OK!",m_context);
            }
        }
    }

    [Activity(Label = "MyDriver-Driver", MainLauncher = true, Icon = "@drawable/icon")]
    public class Activity1 : Activity
    {
        private void CreateAlert()
        {

            AlertDialog.Builder builder = new AlertDialog.Builder(this);
            builder.SetTitle("GPS is Off")
                .SetMessage("You need GPS to you this application."+ "\n" +
                             "Do you want to go to settings menu?")
                .SetPositiveButton("Setting",
                    (sender, e) =>
                    {
                        Intent intent = new Intent(Android.Provider.Settings.ActionLocationSourceSettings);
                        StartActivity(intent);
                        this.Finish();
                    })
                    .SetNegativeButton("No", (sender, e) => this.Finish());

            AlertDialog alert = builder.Create();
            alert.Show();
        }
        protected override void OnCreate(Bundle bundle)
        {
            base.OnCreate(bundle);
            // Set our view from the "main" layout resource
            SetContentView(Resource.Layout.Main);

            Android.Util.Log.Info("EXC_logstart", "**************** starting driver module ****************");

            Boolean isGPSEnabled = false;
            Boolean isNetworkEnabled = false;
            LocationManager _locationManager;
            _locationManager = (LocationManager)GetSystemService(LocationService);
            isGPSEnabled = _locationManager.IsProviderEnabled(LocationManager.GpsProvider);

            // getting network status
            isNetworkEnabled = _locationManager.IsProviderEnabled(LocationManager.NetworkProvider);

            if (!isGPSEnabled && !isNetworkEnabled)
            {
                CreateAlert();
            }

            // Get our button from the layout resource,
            // and attach an event to it
            EditText eTextUsername = FindViewById<EditText>(Resource.Id.UserNameBox);
            EditText eTextPassword = FindViewById<EditText>(Resource.Id.PasswordBox);
            EditText eTextCarNum = FindViewById<EditText>(Resource.Id.CarNumBox);
            Button viewPrefsBtn = FindViewById<Button>(Resource.Id.BtnViewPrefs);
            Button button = FindViewById<Button>(Resource.Id.MyButton);

            button.Click += delegate 
            {
                if (eTextCarNum.Text != "" && eTextPassword.Text != "" && eTextUsername.Text != "")
                {
                    DriverLogon driver = new DriverLogon();
                    driver.userName = eTextUsername.Text;
                    driver.password = eTextPassword.Text;
                    driver.carNum = eTextCarNum.Text;
                    DriverLogonAsync asyDriver = new DriverLogonAsync(this, driver);
                    asyDriver.Execute();
                }
            };

            viewPrefsBtn.Click += (sender, e) =>
            {
                StartActivity(typeof(PreferencesActivity));
            };
        }
    }
}

Answer 1

Not sure about monodroid, but generally in your application all Activities which requare authorization must be subclassed from one activity which checks in onResume that the user has valid session (You store flag about successfully login or session id after login in memory, for instance in your Application class or any appropriate singleton). Then

• if check failed – return user to login screen
• if successfull – do nothing, just show them activity what he wants

To avoid problem with activity stack (pressing home button returns to login screen) and remove LoginActivity from it use android:noHistory="true" inside your manifest or related property via Intent