private async void _onPropertyChanged(ActivateableViewModel oldVal, ActivateableViewModel newVal)
{
// this is only to support cases where the owner view model
// changes the property without a proper call to Navigate
// but when you do call navigate, it will have already happened
// by the time we get here.
// Note that when performed like this, the calls to this method
// is not "awaited" so exceptions that occur here will not be caught
await _ensureActivationState(oldVal, newVal);
}
private async Task _ensureActivationState(ActivateableViewModel oldVm, ActivateableViewModel newVm)
{
if ((oldVm != null) && (oldVm.IsActive))
{
await oldVm.Deactivate();
}
if ((newVm != null) && (!newVm.IsActive))
{
await newVm.Activate();
}
}
public async Task Start(Region region, ActivateableViewModel parent, string propertyName)
{
Region = region;
Parent = parent;
Property = Parent.GetType().GetProperty(propertyName);
Parent.Activated += (s, e) => _onParentActivated();
Parent.Deactivated += (s, e) => _onParentDeactivated();
Parent.Observe <ActivateableViewModel>(propertyName, this, _onPropertyChanged);
if (Parent.IsActive)
{
_onParentActivated();
}
var vm = _getViewModel();
if ((vm != null) && (!vm.IsActive))
{
await vm.Activate();
}
}
private void _setViewModel(ActivateableViewModel value)
{
Property.SetValue(Parent, value);
}
