Odtnhj

I want to create a app that counts down the selectedtime. But I am having a weird problem and I do not know what I am doing wrong.

Here is my timer, it will be called everytime the property of the picker changes. When I select a time the code only removes 1 second and then it doesn't update anymore.

Picker.PropertyChanged += (sender, e) =>
 
 if (e.PropertyName == TimePicker.TimeProperty.PropertyName)
 
 Device.StartTimer(TimeSpan.FromSeconds(1), () =>
 
 clockViewModel.SelectedTime = Picker.Time.Subtract(TimeSpan.FromSeconds(1));
 return true;
 );
 
 ;

I also tried to print a value that kept updating in the value:

public int i = 0;

 private void StartTimer()
 
 Device.StartTimer(TimeSpan.FromSeconds(1), () =>
 
 clockViewModel.SelectedTime = Picker.Time.Subtract(TimeSpan.FromSeconds(1));
 label.Text = i;
 i++;
 return true;
 );
 

The value kept increasing, so I know for sure that it is doing something.

This is my modelview:

public class ClockViewModel : BaseViewModel
 
 private TimeSpan selectedTime;

 public TimeSpan SelectedTime
 
 get => selectedTime;
 set
 
 selectedTime = value;
 NotifyPropertyChanged();
 
 
 

Anyone know what I am doing wrong here?

The timer runs in a different thread. If you want to run something on the main thread, where the UI is, then you have to use the Device.BeginInvokeOnMainThread() method. Like this:

Device.StartTimer(TimeSpan.FromSeconds(1), () =>

 Device.BeginInvokeOnMainThread (() => 
 
 clockViewModel.SelectedTime = Picker.Time.Subtract(TimeSpan.FromSeconds(1));
 label.Text = i;
 );

 i++;
 return true;
);