Xamarin C# MainAvtivity.Intent is null - c#

I'm Creating a Call Diverting app using Xamarin. What i am doing is with the press of a button a command is triggerd and using DependencyService i call the Android specific implementaion of the Call Diverter Method.
Now I'm having a problam where the instance of the MainActivity Context for the StartActivity Method is null. I'm suspecting that this is the cause of the error i get when i running the app: 'Target of StartActivity is null (NullReferenceException)'
but i dont know how to fix this. i thought i'm doing everything right but i'm getting an exception.
this is my code so far: Android Project Call diverting method implementation
[assembly: Dependency(typeof(CallDiverter_Android))]
namespace CallDiverter2.Droid
{
public class CallDiverter_Android : ICallDiverter
{
public void DivertCall(string callForwardString)
{
var context = MainActivity.Instance;
//Divert call code
try
{
//String callForwardString = "**21*1234567890#";
Intent callIntent = new Intent(Intent.ActionCall); // ACTION_CALL
Android.Net.Uri uri = Android.Net.Uri.Parse(callForwardString);
callIntent.SetData(uri);
context.StartActivity(callIntent);
//Forms.Context.StartActivity(callIntent);
}
catch (Exception)
{
throw;
}
}
public void StopCallDiverting()
{
//Stop the call diverting action
}
}
}
The instance in the MainActivity class:
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
internal static MainActivity Instance { get; private set; }
protected override void OnCreate(Bundle bundle)
{
Instance = this;
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(bundle);
global::Xamarin.Forms.Forms.Init(this, bundle);
LoadApplication(new App());
}
}

Related

java.lang.IllegalArgumentException: No such service ComponentInfo{/com.SampleApp.AttendanceApp.ServiceClass}

I am using Xamarin Android to build an app which should allow the app to keep sending a driver's location every 15 minutes so that I can keep track of his movement. I used JobScheduler to get this done. My project is very simple now and only contains the following 3 files:
MainActivity.cs
AttendancePage.cs (Content page, interact with UI button to start the service)
ServiceClass.cs
Methods in Main Activity.cs
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
scheduler = (JobScheduler)GetSystemService(JobSchedulerService);
LoadApplication(new App()); //This line will then jump to AttendancePage.cs
}
public void ScheduleJob()
{
ComponentName componentName = new ComponentName(this, Java.Lang.Class.FromType(typeof(ServiceClass)));
JobInfo info = new JobInfo.Builder(123, componentName)
.SetPersisted(true)
.SetPeriodic(60000)
.Build();
int resultCode = scheduler.Schedule(info); //The error show when hit this line.
if (resultCode == JobScheduler.ResultSuccess)
{
Log.Info("Message", "Job Schedule!");
}
else
{
Log.Info("Message", "Job shceduling failed");
}
}
public void CancelJob()
{
scheduler.Cancel(123);
}
AttendancePage.cs
public partial class AttendancePage : ContentPage
{
MainActivity main = new MainActivity();
public AttendancePage()
{
InitializeComponent();
Title = "Attendance App";
}
//Button OnClickEvent
async void ScheduleJob(object s, EventArgs e)
{
main.ScheduleJob();
}
//Button OnClickEvent
async void CancelJob(object s, EventArgs e)
{
main.CancelJob();
}
}
ServiceClass.cs
[Service(Name = "com.SampleApp.AttendanceApp.ServiceClass", Permission = "android.permission.BIND_JOB_SERVICE")]
public class ServiceClass : JobService
{
public ServiceClass()
{
}
public override bool OnStartJob(JobParameters jobParamsOnStart)
{
doBackgroundWork(jobParamsOnStart);
return true;
}
private void doBackgroundWork(JobParameters jobParam)
{
//My code to send driver's location
TestingPage.GetGPS();
JobFinished(jobParam, false);
}
public override bool OnStopJob(JobParameters jobParamsOnStop)
{
return false;
}
}
I have added the service tag inside AndroidManifest.xml as well.
<service android:name=".ServiceClass"
android:permission="android.permission.BIND_JOB_SERVICE"
android:exported="true" />
I have no idea why the error is still there. The error is from the line scheduler.Schedule(JobInfo). Anyone has another possible solution? I am frustrated on solving this. Will the reason be I can't debug on the service but only can straight away run in release mode? Please help.
Froms shared code it works in Xamarin.Android project , however here is a Xamarin.Forms project . It can not work.
In AttendancePage.cs , you create a new MainActivity to invoke the native method ScheduleJob and CancelJob . This will not find the JobScheduler in native ,then it will return null .
No such service ComponentInfo{/com.SampleApp.AttendanceApp.ServiceClass}
If you want to invoke native method , you can have a try with DependencyService in Xamarin Forms .
At least need to create a Interface in Forms to invoke :
public interface IJobSchedulerService
{
//Start JobSchedule
void StartJobSchedule();
//Cancel JobSchedule
void CancelJobSchedule();
}
Then can invoke in Xamarin Forms as follow :
async void ScheduleJob(object s, EventArgs e)
{
DependencyService.Get<IJobSchedulerService>().StartJobSchedule();
}
//Button OnClickEvent
async void CancelJob(object s, EventArgs e)
{
DependencyService.Get<IJobSchedulerService>().CancelJobSchedule();
}
Now you need to implement the IJobSchedulerService in native android .Create the JobSchedulerDependcenyService:
public class JobSchedulerDependcenyService : IJobSchedulerService
{
JobScheduler jobScheduler;
public JobSchedulerDependcenyService()
{
jobScheduler = (JobScheduler)MainActivity.Instance.GetSystemService(Android.Content.Context.JobSchedulerService);
}
public void StartJobSchedule()
{
ComponentName componentName = new ComponentName(MainActivity.Instance, Java.Lang.Class.FromType(typeof(DownloadJob)));
JobInfo jobInfo = new JobInfo.Builder(1, componentName)
.SetOverrideDeadline(0)
.Build();
//var jobScheduler = (JobScheduler)GetSystemService(JobSchedulerService);
var scheduleResult = jobScheduler.Schedule(jobInfo);
if (JobScheduler.ResultSuccess == scheduleResult)
{
var snackBar = Snackbar.Make(MainActivity.Instance.FindViewById(Android.Resource.Id.Content), "jobscheduled_success", Snackbar.LengthShort);
snackBar.Show();
}
else
{
var snackBar = Snackbar.Make(MainActivity.Instance.FindViewById(Android.Resource.Id.Content), "jobscheduled_failure", Snackbar.LengthShort);
snackBar.Show();
}
}
public void CancelJobSchedule()
{
jobScheduler.CancelAll();
}
}
Here you will find the MainActivity.Instance inside it , that's a static instance defined by self in MainActivity.
public static MainActivity Instance { set; get; }
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(savedInstanceState);
Instance = this;
Xamarin.Essentials.Platform.Init(this, savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
LoadApplication(new App());
}

Xamarin Forms Service with IsolatedProcess crashes

I'm developing an Android application with Xamarin Forms that is composed of an interface and also a background service.
I need that the service works also when the interface application is closed.
If I add "IsolatedProcess = true" into the service the graphical interface still works but the service crashes.
I read a lot of posts with possible solutions but they don't work. (I tried to compile in release mode and also to remove "Use Shared Runtime" flag).
I'm compiling with Android 8.1 (Oreo) as Target Framework.
The target environment is Android 4.2.
I start the service into OnCreate method of the MainActivity class:
Intent testIntent = new Intent(this.BaseContext, typeof(TestService));
StartService(testIntent);
The service class:
[Service(IsolatedProcess = true, Exported = true, Label = "TestService")]
public class TestService : Service
{
public override IBinder OnBind(Intent intent)
{
return null;
}
public override void OnCreate()
{
base.OnCreate();
}
[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
Device.StartTimer(new TimeSpan(0, 0, 40), () =>
{
//Code executed every 40 seconds
});
base.OnStartCommand(intent, flags, startId);
return StartCommandResult.Sticky;
}
public override bool StopService(Intent name)
{
return base.StopService(name);
}
}
If I remove "IsolatedProcess = true" the service works but it will be stopped when I will close the application interface process.
I solved the issue by changing the value of the attribute IsolatedProcess to true, removing the Device.StartTimer instruction and by introducing a BroadcastReceiver.
MainActivity class:
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsAppCompatActivity
{
public static Intent testServiceIntent;
protected override void OnCreate(Bundle savedInstanceState)
{
TabLayoutResource = Resource.Layout.Tabbar;
ToolbarResource = Resource.Layout.Toolbar;
base.OnCreate(savedInstanceState);
global::Xamarin.Forms.Forms.Init(this, savedInstanceState);
testServiceIntent = new Intent(this.BaseContext, typeof(TestService));
LoadApplication(new App());
}
}
The service class:
[Service(IsolatedProcess = false, Exported = true, Label = "TestService")]
public class TestService : Service
{
System.Threading.Timer _timer;
public override IBinder OnBind(Intent intent)
{
return null;
}
public override void OnCreate()
{
base.OnCreate();
}
[return: GeneratedEnum]
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
businessLogicMethod();
base.OnStartCommand(intent, flags, startId);
return StartCommandResult.Sticky;
}
public void businessLogicMethod()
{
//My business logic in a System.Threading.Timer
}
}
The Broadcast Receiver class:
[BroadcastReceiver]
[IntentFilter(new[] { Intent.ActionBootCompleted })]
public class TestApplicationBroadcastReceiver : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
Log.Info("TestApp", "******* Loading Application *******");
try
{
if (intent.Action.Equals(Intent.ActionBootCompleted))
{
Intent service = new Intent(context, typeof(TestService));
service.AddFlags(ActivityFlags.NewTask);
context.StartService(service);
}
}
catch (Exception ex)
{
Log.Error("TestApp", "******* Error message *******: " + ex.Message);
}
}
}
I hope that can be useful for someone.

You MUST call Rg.Plugins.Popup.Popup.Init(); prior to using it

System.InvalidOperationException:
You MUST call Rg.Plugins.Popup.Popup.Init(); prior to using it.
i already put Rg.Plugins.Popup.Popup.Init() in appdelegate.cs in IOS
but it still give me same error
what should i do for it?
Simply, you need to call Rg.Plugins.Popup.Popup.Init(); on startup
Andriod Example
namespace HelloXamarinFormsWorld.Android
{
[Activity(Label = "HelloXamarinFormsWorld", MainLauncher = true,
ConfigurationChanges = ConfigChanges.ScreenSize | ConfigChanges.Orientation)]
public class MainActivity : global::Xamarin.Forms.Platform.Android.FormsApplicationActivity
{
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
// !!!!!! here !!!!!
Rg.Plugins.Popup.Popup.Init(this, bundle);
Xamarin.Forms.Forms.Init(this, bundle);
LoadApplication (new App ());
}
}
}
IOS Example
[Register("AppDelegate")]
public partial class AppDelegate : global::Xamarin.Forms.Platform.iOS.FormsApplicationDelegate
{
public override bool FinishedLaunching(UIApplication app, NSDictionary options)
{
// !!!!!! here !!!!!
Rg.Plugins.Popup.Popup.Init();
global::Xamarin.Forms.Forms.Init ();
LoadApplication (new App ());
return base.FinishedLaunching (app, options);
}
}
Please read the documentation here
https://github.com/rotorgames/Rg.Plugins.Popup/wiki/Getting-started

BroadcastReceiver does not receive broadcast

My BroadcastReceiver does not receive anything. Most likely its my setup that is wrong, because I was not able to find any good examples on this. I need my receiver to receive something in my MainActivity, and change a View. I have almost the same code in an Android project, and here it is working, however BroadcastReceivers seems to be implemented a tiny bit differently in Xamarin (in Android, I can make a new BroadcastReceiver almost like an object, but in Xamarin, or C#, it seems I must make my own class and thus do not have the same possibilities to directly reference the views). If I get this to work, I will post a full working example for everyone too.
Here is how I have tried to set it up:
[Activity(Label = "GetLocation.Droid", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
Button button;
protected override void OnCreate(Bundle bundle)
{
// ... various OnCreate() code
LocationBroadcastReciever lbr = new LocationBroadcastReciever();
RegisterReceiver(lbr, new IntentFilter("test"));
}
public void SetButtonText(string text)
{
button.Text = text;
}
}
[BroadcastReceiver]
public class LocationBroadcastReciever : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
/* My program never get this far, so I have not been able
to confirm if the bellow code works or not (its from
another example I saw). */
//EDIT: It does NOT work. See my answer for a working example
string text = intent.GetStringExtra("title");
((MainActivity)context).SetButtonText(text);
InvokeAbortBroadcast();
}
}
And in my IntentService I have this method that actually runs, but never arrives at my receiver.
private void SendBroadcast(double lat, double lng, string activity)
{
Intent intent = new Intent("test");
intent.PutExtra("title", "Updated");
LocalBroadcastManager.GetInstance(this).SendBroadcast(intent);
}
This is pretty much the same code as I have in my working Android (only tweaked the BroadcastReceiver and minor adjustments to make it compile).
Can anyone see whats wrong??
EDIT
Finally got this whole thing to work. You can see my answer for a full, clean example.
Local
You register receiver as global, but send intents via LocalBroadcastManager. If you want to use this manager you should register your receiver like this:
LocalBroadcastManager.GetInstance(this).RegisterReceiver(lbr, filter);
You can find more about LocalBroadcastManager here.
Global
Or if you want to use global broadcasts, you should create intent by type:
var intent = new Intent(this, typeof(LocationBroadcastReciever));
and send it via android Context (in your service):
this.SendBroadcast(intent);
Also you can use intent with action, but it requires IntentFilter attribute on your receiver:
[IntentFilter(new []{ "test" })]
[BroadcastReceiver]
public class LocationBroadcastReciever : BroadcastReceiver { ... }
For the sake of future search results, here is a clean example of my code with a working BroadcastReceiver
// ** MainActivity
namespace GetLocation.Droid
{
[Activity(Label = "GetLocation.Droid", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
//I initialize my view(s) here to access them from outside of OnCreate().
Button button;
//I found this in an Android BroadcastReceiver example of how to access the MainActivity from the BroadcastReceiver.
private static MainActivity ins;
public static MainActivity getInstace()
{
return ins;
}
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
SetContentView(Resource.Layout.Main);
button = FindViewById<Button>(Resource.Id.myButton);
ins = this;
button.Click += delegate
{
Intent intent = new Intent(this, typeof(MyIntentService));
StartService(intent);
};
LocationBroadcastReciever lbr = new LocationBroadcastReciever();
LocalBroadcastManager.GetInstance(this).RegisterReceiver(lbr, new IntentFilter("test"));
}
public void SetButtonText(string text)
{
button.Text = text;
}
}
[BroadcastReceiver]
[IntentFilter(new[] { "test" })]
public class LocationBroadcastReciever : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
string text = intent.GetStringExtra("title");
MainActivity.getInstace().SetButtonText(text);
}
}
}
And in my IntentService
namespace GetLocation.Droid
{
[Service]
[IntentFilter(new String[] { "com.mytos.MyIntentService" })]
public class MyIntentService : IntentService
{
protected override void OnHandleIntent(Intent intent)
{
SendBroadcast("My message");
}
private void SendBroadcast(string message)
{
//Here you can of course send whatever variable you want. Mine is a string
Intent intent = new Intent("test");
intent.PutExtra("title", message);
LocalBroadcastManager.GetInstance(this).SendBroadcast(intent);
}
}
}
A couple of things:
First, you need the [IntentFilter] on the receiver. So it should look like....
[BroadcastReceiver(Enabled = true)]
[IntentFilter(new [] { "test" })]
public class LocationBroadcastReciever : BroadcastReceiver
{
public override void OnReceive(Context context, Intent intent)
{
/* My program never get this far, so I have not been able
to confirm if the bellow code works or not (its from
another example I saw). */
string text = intent.GetStringExtra("title");
((MainActivity)context).SetButtonText(text);
InvokeAbortBroadcast();
}
}
That should get you past your issue.
Second, you should register and unregister the reciever. So you should register in the OnResume and unregister in OnPause.
[Activity(Label = "GetLocation.Droid", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
LocationBroadcastReciever _lbr;
Button button;
protected override void OnCreate(Bundle bundle)
{
// ... various OnCreate() code
}
protected override void OnResume()
{
base.OnResume();
_lbr = new LocationBroadcastReciever();
RegisterReceiver(lbr, new IntentFilter("test"));
}
protected override void OnPause()
{
UnregisterReceiver(_lbr);
base.OnPause();
}
public void SetButtonText(string text)
{
button.Text = text;
}
}
Note: these changes are what I saw different between your code and my code for a working broadcast receiver. Whether my changes are necessary or not, I'm not entirely sure.

Xamarin Android Background Service crashes when the Application get closed

Hello, I want to build an app, in which you can start a service, which runs intependenly and creates a notification, and this service should constantly proof, if the DateTime.Now.Date is bigger than a spezific Date.
When I execute the code below, the notification gets displayed, but when I am closing the app, a few secondes later I get two times an information that the app crashed and I dont know why.
I cant even debug the code because this anly happens when the application is closed....
I hope you can help me thanks!
Here is my code:
namespace App
{
[Activity(Label = "App", MainLauncher = true, Icon = "#drawable/icon")]
public class MainActivity : Activity
{
int count = 1;
protected override void OnCreate(Bundle bundle)
{
base.OnCreate(bundle);
// Set our view from the "main" layout resource
SetContentView(Resource.Layout.Main);
// Get our button from the layout resource,
// and attach an event to it
Button button = FindViewById<Button>(Resource.Id.MyButton);
button.Click += delegate {
button.Text = string.Format("{0} clicks!", count++);
StartService(new Intent(this, typeof(backgroudservice)));
};
}
}
public class backgroudservice : Service
{
public override IBinder OnBind(Intent intent)
{
return null;
}
public override StartCommandResult OnStartCommand(Intent intent, [GeneratedEnum] StartCommandFlags flags, int startId)
{
newnotification("Title", "Text: ", 0);
new Task(() => {
DoWork();
Thread.Sleep(1000);
}).Start();
return StartCommandResult.Sticky;
}
public void DoWork()
{
if (DateTime.Now.Date > Convert.ToDateTime("2016-03-29").Date)
{
cancelnotification(0);
StopSelf();
}
}
public override void OnDestroy()
{
base.OnDestroy();
cancelnotification(0);
}
private void newnotification(string titel, string text, int id)
{
Notification.Builder builder = new Notification.Builder(this)
.SetContentTitle(titel)
.SetContentText(text)
.SetSmallIcon(Resource.Drawable.droidlogo_small)
.SetAutoCancel(false)
.SetVisibility(NotificationVisibility.Public)
.SetContentIntent(PendingIntent.GetActivity(this, 0, new Intent(this, typeof(MainActivity)), PendingIntentFlags.OneShot));
// Build the notification:
Notification notification = builder.Build();
notification.Flags = NotificationFlags.NoClear;
//notification.ContentIntent = new Intent(this,typeof(login));
// Get the notification manager:
NotificationManager notificationManager = GetSystemService(Context.NotificationService) as NotificationManager;
// Publish the notification:
notificationManager.Notify(id, notification);
}
private void cancelnotification(int id)
{
NotificationManager notificationManager = GetSystemService(Context.NotificationService) as NotificationManager;
notificationManager.Cancel(id);
}
}
}
I solved it, I forgot the [Service] above my class, now it works!
[Service]
public class backgroudservice : Service
{
...
}
You might try moving the call to cancelnotification in your service's OnDestroy to before the call to the base method, i.e.:
public override void OnDestroy()
{
cancelnotification(0);
base.OnDestroy();
}

Categories