internal void UpdateView(object view, DataTemplate viewTemplate, ref UIView uiView, ref VisualElement formsElement)
{
// Is view set on the ItemsView?
if (view == null)
{
if (formsElement != null)
Platform.GetRenderer(formsElement)?.DisposeRendererAndChildren();
uiView?.Dispose();
uiView = null;
formsElement = null;
}
else
{
// Create the native renderer for the view, and keep the actual Forms element (if any)
// around for updating the layout later
(uiView, formsElement) = TemplateHelpers.RealizeView(view, viewTemplate, ItemsView);
}
}
public void Bind(DataTemplate template, object bindingContext, ItemsView itemsView)
{
var oldElement = VisualElementRenderer?.Element;
// Run this through the extension method in case it's really a DataTemplateSelector
var itemTemplate = template.SelectDataTemplate(bindingContext, itemsView);
if (itemTemplate != CurrentTemplate)
{
// Remove the old view, if it exists
if (oldElement != null)
{
oldElement.MeasureInvalidated -= MeasureInvalidated;
oldElement.BindingContext = null;
itemsView.RemoveLogicalChild(oldElement);
ContentView.ClearSubviews();
_size = Size.Zero;
}
// Create the content and renderer for the view
var view = itemTemplate.CreateContent() as View;
// Set the binding context _before_ we create the renderer; that way, it's available during OnElementChanged
view.BindingContext = bindingContext;
var renderer = TemplateHelpers.CreateRenderer(view);
SetRenderer(renderer);
// And make the new Element a "child" of the ItemsView
// We deliberately do this _after_ setting the binding context for the new element;
// if we do it before, the element briefly inherits the ItemsView's bindingcontext and we
// emit a bunch of needless binding errors
itemsView.AddLogicalChild(view);
// Prevents the use of default color when there are VisualStateManager with Selected state setting the background color
// First we check whether the cell has the default selected background color; if it does, then we should check
// to see if the cell content is the VSM to set a selected color
if (SelectedBackgroundView.BackgroundColor == ColorExtensions.Gray && IsUsingVSMForSelectionColor(view))
{
SelectedBackgroundView = new UIView
{
BackgroundColor = UIColor.Clear
};
}
}
else
{
// Same template
if (oldElement != null)
{
if (oldElement.BindingContext == null || !(oldElement.BindingContext.Equals(bindingContext)))
{
// If the data is different, update it
// Unhook the MeasureInvalidated handler, otherwise it'll fire for every invalidation during the
// BindingContext change
oldElement.MeasureInvalidated -= MeasureInvalidated;
oldElement.BindingContext = bindingContext;
oldElement.MeasureInvalidated += MeasureInvalidated;
UpdateCellSize();
}
}
}
CurrentTemplate = itemTemplate;
}