Xamarin和MVVM-如何将View中的Boxview绑定到ViewModel中的Color数组？

Question

I have a two-dimensional array of Xamarin.Forms.Color objects in my ViewModel. I would like to bind this array to a bunch of BoxView objects in my View and set their color based on the array's contents. I know how to bind to properties like string, int or bool on a ViewModel, but if the specific value I want to bind to is a system-provided object like Color, I have no idea.

Code snippets:

ViewModel has this property that I would like to bind to:

public GameGrid<Color> Board;

View is not declared in XAML but instead via C# code. The property I'd like bound is the ColorProperty of a BoxView, like this:

boxView.BindingContext = _viewModel.Board[row, col];
boxView.SetBinding(BoxView.ColorProperty, ".", BindingMode.Default);

Given that the _viewModel.Board property is a cell in a two-dimentional array or type Color, how do I bind to it? The "." is a placeholder - I don't know what I should place there.

The GameGrid class wraps a two-dimensional array, because I figured I would need to implement INotifyPropertyChanged so I can react to individual element changes in this array later, in order to animate a game move. For completeness, its code is here:

public class GameGrid<T> : INotifyPropertyChanged
{
    private T[,] _array;

    public GameGrid(int rows, int columns)
    {
        _array = new T[rows, columns];
    }

    public T this[int a, int b]
    {
        get 
        {
            return _array[a, b];    
        }
        set
        {
            _array[a, b] = value;

            RaisePropertyChanged(nameof(GameGrid<T>));
        }
    }

    public event PropertyChangedEventHandler PropertyChanged;

    private void RaisePropertyChanged(string propertyName)
    {

        PropertyChanged?.Invoke(
            this, new PropertyChangedEventArgs(propertyName));
    }
}

If I change my two-dimensional array to be a simple object, eg;

public class Wrapper
{
    public Color BindThis { get; set; }
}
public GameGrid<Wrapper> Board;

it is pretty trivial to bind to that property like this:

boxView.SetBinding(BoxView.ColorProperty, "BindThis", BindingMode.Default);

but that seems needlessly complicated.

Answer 1

It looks like you're on the right track. A single dot ( . ) is the syntax to bind to the BindingContext itself; not a property on the BindingContext , but the object that is the current BindingContext .

Have you tried just running the code with the . as the Binding expression?

BoxView.Color is of type Xamarin.Forms.Color , so you should be able to bind to that directly.