Accessing activity 2 while foreground is activity 1 (either using OOP or Service in XAMARIN) - oop

Question

i code this from a tutorial for locating your location (but I already made some changes)
using Android.App;
using Android.Widget;
using Android.OS;
using Android.Locations;
using System.Collections.Generic;
using Android.Util;
using System.Linq;
using Java.Lang;
using System.Threading.Tasks;
using System;
using Android.Views;
using Android.Content;
namespace LocatorApp
{
[Activity(Label = "Locator", MainLauncher = true, Icon = "#drawable/locator_ico")]
public class LocatorApp : Activity, ILocationListener
{
static readonly string TAG = "X:" + typeof(LocatorApp).Name;
TextView _addressText;
Location _currentLocation;
LocationManager _locationManager;
Address address;
string _locationProvider;
TextView _locationText;
private double latitude = 0;
private double longitude = 0;
public Location getCurrentLocation() { return _currentLocation; }
public double getLatitude() { return latitude; }
public double getLongitude() { return longitude; }
public Address getAddress() { return address; }
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
_addressText = FindViewById<TextView>(Resource.Id.address_text);
_locationText = FindViewById<TextView>(Resource.Id.location_text);
FindViewById<TextView>(Resource.Id.get_address_button).Click += AddressButton_OnClick;
InitializeLocationManager();
}
public void InitializeLocationManager()
{
_locationManager = (LocationManager)GetSystemService(LocationService);
Criteria criteriaForLocationService = new Criteria
{
Accuracy = Accuracy.Coarse,
PowerRequirement = Power.Medium
};
IList<string> acceptableLocationProviders = _locationManager.GetProviders(criteriaForLocationService, true);
if (acceptableLocationProviders.Any())
{
_locationProvider = acceptableLocationProviders.First();
}
else
{
_locationProvider = string.Empty;
}
Log.Debug(TAG, "Using " + _locationProvider + ".");
}
async void AddressButton_OnClick(object sender, EventArgs eventArgs)
{
if (_currentLocation == null)
{
Toast.MakeText(this, "Still waiting for location.", ToastLength.Short).Show();
}
else
{
try
{
var geoUri = Android.Net.Uri.Parse("geo:" + _currentLocation.Latitude + "," + _currentLocation.Longitude);
var mapIntent = new Intent(Intent.ActionView, geoUri);
StartActivity(mapIntent);
}
catch (System.Exception e)
{
Toast.MakeText(this, "Sorry, there is a problem with geomapping.", ToastLength.Short).Show();
}
}
}
async Task<Address> ReverseGeocodeCurrentLocation()
{
try
{
Geocoder geocoder = new Geocoder(this);
IList<Address> addressList =
await geocoder.GetFromLocationAsync(_currentLocation.Latitude, _currentLocation.Longitude, 10);
Address address = addressList.FirstOrDefault();
return address;
}
catch (System.Exception e)
{
throw;
}
return null;
}
void DisplayAddress(Address address)
{
if (address != null)
{
StringBuilder deviceAddress = new StringBuilder();
for (int i = 0; i < address.MaxAddressLineIndex; i++)
{
deviceAddress.Append(address.GetAddressLine(i));
}
// Remove the last comma from the end of the address.
_addressText.Text = "Address: "+deviceAddress.ToString();
}
else
{
_addressText.Text = "Unable to determine the address. Try again in a few minutes.";
}
}
public async void OnLocationChanged(Location location)
{
Toast.MakeText(this, "Location changed.", ToastLength.Short).Show();
_currentLocation = location;
if (_currentLocation == null)
{
_locationText.Text = "Unable to determine your location. Try again in a short while.";
}
else
{
try
{
_locationText.Text = "Location: " + string.Format("{0:f6},{1:f6}", _currentLocation.Latitude, _currentLocation.Longitude);
Address address = await ReverseGeocodeCurrentLocation();
DisplayAddress(address);
var nMgr = (NotificationManager)GetSystemService(NotificationService);
var notification = new Notification(Resource.Drawable.Icon, "Message from LocatorApp");
var pendingIntent = PendingIntent.GetActivity(this, 0, new Intent(this, typeof(LocatorApp)), 0);
notification.SetLatestEventInfo(this, "LocatorApp", "Location changed!", pendingIntent);
nMgr.Notify(0, notification);
}
catch (Java.Lang.Exception e)
{
_addressText.Text = "Unable to determine the address. Try again in a few minutes.";
Toast.MakeText(this, "Error Occured On Geocoder!", ToastLength.Short).Show();
Log.Error(TAG, e.Message);
}
}
}
public void OnProviderDisabled(string provider) { }
public void OnProviderEnabled(string provider) { }
public void OnStatusChanged(string provider, Availability status, Bundle extras) { }
protected override void OnResume()
{
base.OnResume();
if (_locationManager.IsProviderEnabled(_locationProvider))
{
_locationManager.RequestLocationUpdates(_locationProvider, 100, 0, this);
Toast.MakeText(this, _locationProvider.ToString(), ToastLength.Short).Show();
}
else
{
Toast.MakeText(this, "There is a problem with "+_locationProvider.ToString()+" provider.", ToastLength.Short).Show();
}
}
protected override void OnPause()
{
base.OnPause();
_locationManager.RemoveUpdates(this);
}
}
}
(i'm just having my experiment)
what I want is to run activity B while foreground is in activity A, just like a basic OOP . but my problem is, I don't know how to make it run. I can't also jump to activity B since it has an oncreate method. I instantiated it and can get the variables values but they are null (seems there is no process happened) . What can be a best solution for this.
note: I am currently looking how to use service for background processing but also i don't know how to run this code after I typed it from a tutorial :( there is only a tutorial for creating a service part but no tutorial for buttons to access it :(
using System;
using Android.App;
using Android.Content;
using Android.OS;
using Android.Util;
using System.Threading;
namespace LocatorApp
{
[Service]
class SimpleService : Service
{
static readonly string TAG = "X:" + typeof(SimpleService).Name;
static readonly int TimerWait = 4000;
Timer _timer;
public override StartCommandResult OnStartCommand(Intent intent, StartCommandFlags flags, int startId)
{
Log.Debug(TAG, "OnStartCommand called at {2}, flags={0}, startid={1}", flags, startId, DateTime.UtcNow);
_timer = new Timer(o => { Log.Debug(TAG, "Hello from SimpleService. {0}", DateTime.UtcNow); },
null,
0,
TimerWait);
return StartCommandResult.NotSticky;
}
public override void OnDestroy()
{
base.OnDestroy();
_timer.Dispose();
_timer = null;
Log.Debug(TAG, "SimpleService destroyed at {0}.", DateTime.UtcNow);
}
public override IBinder OnBind(Intent intent)
{
// This example isn't of a bound service, so we just return NULL.
return null;
}
}
}
I want to know both (OOP way and service way) since not at all time we are required to use the service.

Answer 1

what I want is to run activity B while foreground is in activity A, just like a basic OOP . but my problem is, I don't know how to make it run. I can't also jump to activity B since it has an oncreate method.
You can call Context.StartActivity inside your Activity with following codes:
StartActivity(new Android.Content.Intent(this, typeof(ActivityB)));
And StartActivity will call OnCreate method in ActivityB to create a new instance of ActivityB.
For details about Starting Activities, please refer to Starting Activities and Getting Results.
I am currently looking how to use service for background processing but also i don't know how to run this code after I typed it from a tutorial :( there is only a tutorial for creating a service part but no tutorial for buttons to access it :(
Similar like Activity Context.StartService offers a way to start a Service:
StartService (new Intent (this, typeof(DemoService)));
This will call the OnStartCommand method inside your Service class.
For details about usage of Service, please refer to Implementing a Service.