Update textview in android custom notification - xamarin

Question

I have a custom local notification implementing remoteview comprising of three buttons and a textview. Button click in notification changes volume of ringer but I want to increment a variable count each time the up button click or decrement then count each time downbutton click. I have problem updating textview as the broadcaster class can't access it directly. I tried a method from a post, but I can't make it work.
I get null exception at tvUpdate.text=t;
Any idea would be appreaciated. Thanks
RemoteView
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="horizontal"
android:layout_width="match_parent"
android:layout_height="75dp"
android:weightSum="100"
android:padding="5dp"
android:background="#969696"
android:minWidth="25px"
android:minHeight="25px">
<Button
android:text="Vol_Up"
android:layout_width="0dp"
android:layout_weight="25"
android:background="#drawable/roundcnr"
android:layout_height="wrap_content"
android:layout_margin="5dp"
android:textColor="#FFFFFF"
android:id="#+id/btnVolUp" />
<Button
android:text="V_Down"
android:layout_width="0dp"
android:layout_weight="25"
android:layout_margin="5dp"
android:textColor="#FFFFFF"
android:background="#drawable/roundcnr"
android:layout_height="wrap_content"
android:id="#+id/btnVolDown" />
<Button
android:text="Silent"
android:layout_width="0dp"
android:layout_weight="25"
android:layout_margin="5dp"
android:background="#drawable/roundcnr"
android:layout_height="wrap_content"
android:textColor="#FFFFFF"
android:id="#+id/btnVolSilent" />
<TextView
android:text="Status"
android:layout_width="0dp"
android:layout_weight="25"
android:textColor="#FFFFFF"
android:layout_height="wrap_content"
android:id="#+id/tvVol" />
</LinearLayout>
Broadcaster Class
namespace RingerTest
{
[BroadcastReceiver]
public class myBroadCastR : BroadcastReceiver
{
public double counter { get; set; }
public override void OnReceive(Context context, Intent intent)
{
if(intent.Action== "VolumeUp")
{
counter += 6;
// Toast.MakeText(context,"VolumeUp",ToastLength.Long).Show();
AudioManager audioManager = (AudioManager)context.GetSystemService(Context.AudioService);
audioManager.AdjustSuggestedStreamVolume(Adjust.Raise, Stream.Ring, VolumeNotificationFlags.PlaySound);
try
{
MainActivity.getinstance().updateTextView(counter.ToString() + "%");
}
catch (Exception ex)
{
}
}
else if (intent.Action == "VolumeDown")
{
counter -= 6;
// Toast.MakeText(context, "VolumeDown",ToastLength.Long).Show();
AudioManager audioManager = (AudioManager)context.GetSystemService(Context.AudioService);
audioManager.AdjustSuggestedStreamVolume(Adjust.Lower, Stream.Ring, VolumeNotificationFlags.PlaySound);
try
{
MainActivity.getinstance().updateTextView(counter.ToString() + "%");
}
catch (Exception ex)
{
}
}
else if (intent.Action == "Silent")
{
counter = 0;
// Toast.MakeText(context, "VolumeDown",ToastLength.Long).Show();
AudioManager audioManager = (AudioManager)context.GetSystemService(Context.AudioService);
audioManager.RingerMode = RingerMode.Silent;
MainActivity.getinstance().updateTextView(counter.ToString()+"%");
}
}
}
}
MainActivity
namespace RingerTest
{
[Activity(Label = "RingerTest", MainLauncher = true)]
public class MainActivity : Activity
{
public static MainActivity ins;
private myBroadCastR myBroadl;
protected override void OnCreate(Bundle savedInstanceState)
{
base.OnCreate(savedInstanceState);
ins = this;
// Set our view from the "main" layout resource
SetContentView(Resource.Layout.Main);
var myreceiver = new myBroadCastR();
var intentfilter = new IntentFilter();
intentfilter.AddAction("VolumeUp");
intentfilter.AddAction("VolumeDown");
intentfilter.AddAction("Silent");
RegisterReceiver(myreceiver, intentfilter);
Button btnNotify = FindViewById<Button>(Resource.Id.button1);
btnNotify.Click += BtnNotify_Click;
}
public static MainActivity getinstance()
{
return ins;
}
public void updateTextView(string t)
{
MainActivity.ins.RunOnUiThread(() =>
{
TextView tvUpdate = FindViewById<TextView>(Resource.Id.tvVol);
tvUpdate.Text = t;
});
}
private void BtnNotify_Click(object sender, System.EventArgs e)
{
const int requestID = 1;
//Volume Up
Intent intent_V_UP = new Intent("VolumeUp");
PendingIntent pIntent_V_UP = PendingIntent.GetBroadcast(this, requestID, intent_V_UP, PendingIntentFlags.UpdateCurrent);
//Volume Down
Intent intent_V_Down = new Intent("VolumeDown");
PendingIntent pIntent_V_Down = PendingIntent.GetBroadcast(this, requestID, intent_V_Down, PendingIntentFlags.UpdateCurrent);
//Silent
Intent intent_Silent = new Intent("Silent");
PendingIntent pIntent_Silent = PendingIntent.GetBroadcast(this, requestID, intent_Silent, PendingIntentFlags.UpdateCurrent);
Notification.Builder builder = new Notification.Builder(this);
builder.SetSmallIcon(Resource.Drawable.addContact);
/*
builder.SetContentTitle("VolControl");
builder.AddAction(Resource.Drawable.addContact, "VolDown", pIntent_V_Down);
builder.AddAction(Resource.Drawable.addContact, "VolUP", pIntent_V_UP);*/
//Custom View for Notification
RemoteViews remoteViews = new RemoteViews(this.PackageName, Resource.Layout.customNotification);
//On Button Click in CustomView
remoteViews.SetOnClickPendingIntent(Resource.Id.btnVolUp, pIntent_V_UP);
remoteViews.SetOnClickPendingIntent(Resource.Id.btnVolDown, pIntent_V_Down);
remoteViews.SetOnClickPendingIntent(Resource.Id.btnVolSilent, pIntent_Silent);
Notification notification = builder.Build();
notification.BigContentView = remoteViews;
notification.Flags = NotificationFlags.NoClear;
NotificationManager notificationManager = (NotificationManager)GetSystemService(NotificationService);
notificationManager.Notify(1, notification);
}
}
}