MvxSpinner in Mvvmcross - mvvmcross

Question

I have three MvxSpinners in my android view.
These spinners are binded to three different lists.
and Mode of data binding is TwoWay for these spinners.i.e. when this view is
displayed,all of these three spinners are get displayed with the predefined values.
When user change the value in first spinner,then second spinner will be clear and
get loaded with new values based on the selected value in first spinner.
How can I achieve this?

Answer 1

There's many ways to accomplish this, where the code placement is really up to you. Overall the idea would be to have a "SelectedItem" object that you can pass into your method and "Load" the next List.
Please keep in mind that this code is more traditional MVVM, but can easily be converted to MVVMCross equivalent. I believe all these types should be supported by MVVMCross.
private MyFirstObject _selectedFirstObject;
public MyFirstObject SelectedFirstObject
{
get { return _selectedFirstObject; }
set
{
_selectedFirstObject = value;
RaisePropertyChanged("SelectedFirstObject");
if(value != null)
LoadMySecondObjects(value);
}
}
private ObservableCollection<MyFirstObject> _myFirstObjects;
public ObservableCollection<MyFirstObject> MyFirstObjects
{
get { return _myFirstObjects; }
set
{
_myFirstObjects = value;
RaisePropertyChanged("MyFirstObjects");
}
}
private ObservableCollection<MySecondObject> _mySecondObjects;
public ObservableCollection<MySecondObject> MySecondObjects
{
get { return _mySecondObjects; }
set
{
_mySecondObjects = value;
RaisePropertyChanged("MySecondObjects");
}
}
public void LoadMySecondObjects(MyFirstObject current)
{
//Wherever you're pulling data from
MySecondObjects = MyDataService.GetAll(current);
}
protected void RaisePropertyChanged(string propertyName)
{
PropertyChangedEventHandler handler = PropertyChanged;
if (handler != null)
{
handler(this, new PropertyChangedEventArgs(propertyName));
}
}
public event PropertyChangedEventHandler PropertyChanged;

Answer 2

I had the same problem but only if you add null value (as a default value) to your ItemsSource and try to reset SelectedItem to null. SelectedItem is changed in ViewModel but not in the spinner. In that case there's number of solutions but I used message to inform View to set selected item
public class SpinnerSelectionChanged : MvxMessage
{
public SpinnerSelectionChanged(object sender, string spinnerName, int position): base(sender)
{
SpinnerName = spinnerName;
Position = position;
}
public string SpinnerName { get; set; }
public int Position { get; set; }
}
in View
private void OnSpinnerSelectionChanged(SpinnerSelectionChanged obj)
{
switch (obj.SpinnerName)
{
case "City":
_spinnerCity.SetSelection(obj.Position);
break;
case "Office":
_spinnerOffice.SetSelection(obj.Position);
break;
}
}