I'm using MvvmCross to databind my ViewModel to an Android View layout.
From the SimpleBinding example I can see that to bind a value to a property I do this:
so Text is bound to the SubTotal property of the ViewModel. But how do I bind to more than one property? In my case I want to bind a ViewModel property called HigherLower to the TextColor attribute of the layout element. I can't add another MvxBind and I can't set MvxBind to an array.
The answer....
The format of the JSON used in the binding expression is a Dictionary of namedMvxJsonBindingDescriptions
public class MvxJsonBindingDescription
{
public string Path { get; set; }
public string Converter { get; set; }
public string ConverterParameter { get; set; }
public string FallbackValue { get; set; }
public MvxBindingMode Mode { get; set; }
}
This is used with:
- the dictionary Key name being the target (View) property for the binding.
- the binding
Path
property being the source (DataContext) property for the binding - ifPath
is not specified then the whole DataContext itself is the binding source.
For Activity/View level axml the DataContext is the ViewModel - but for sub-View axml then the DataContext will normally be a child object of the ViewModel - e.g. inside a ListView the DataContext might be an item inside a List or ObservableCollection owned by the ViewModel.
To specify multiple bindings you can use JSON like:
{
'TargetProperty1':{'Path':'SourceProperty1'},
'TargetProperty2':{'Path':'SourceProperty2'}
}
For your particular example this might be:
local:MvxBind="
{
'Text':{'Path':'SubTotal','Converter':'Float'},
'TextColor':{'Path':'HigherLower','Converter':'MyColorConverter'}
}"
where your ViewModel is something like:
public class MyViewModel : IMvxViewModel
{
public float SubTotal { get; set; }
public bool HigherLower { get; set; }
// more code here
}
and your converter is something like:
public class MyColorConverter : MvxBaseColorConverter
{
protected override MvxColor Convert(object value, object parameter, CultureInfo culture)
{
return ((bool)value) ? new MvxColor(255,0,0) : new MvxColor(0,255,0);
}
}
and where that converter is initialized during Setup - e.g. see how the properties of the Converters class are used in TwitterSearch
One sample that shows Multiple Bindings at work is BestSellers - see Click and Text bound in the list itemhttps://github.com/slodge/MvvmCross/blob/master/Sample%20-%20BestSellers/BestSellers/BestSellers.Droid/Resources/Layout/ListItem_Category.axml
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