public void ValidateMappingAndAutoRecycling()
{
ItemsRepeater repeater = null;
ScrollViewer scrollViewer = null;
RunOnUIThread.Execute(() =>
{
var layout = new MockVirtualizingLayout()
{
MeasureLayoutFunc = (availableSize, context) =>
{
var element0 = context.GetOrCreateElementAt(index: 0);
// lookup - repeater will give back the same element and note that this element will not
// be pinned - i.e it will be auto recycled after a measure pass where GetElementAt(0) is not called.
var element0lookup = context.GetOrCreateElementAt(index: 0, options: ElementRealizationOptions.None);
var element1 = context.GetOrCreateElementAt(index: 1, options: ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle);
// forcing a new element for index 1 that will be pinned (not auto recycled). This will be
// a completely new element. Repeater does not do the mapping/lookup when forceCreate is true.
var element1Clone = context.GetOrCreateElementAt(index: 1, options: ElementRealizationOptions.ForceCreate | ElementRealizationOptions.SuppressAutoRecycle);
Verify.AreSame(element0, element0lookup);
Verify.AreNotSame(element1, element1Clone);
element0.Measure(availableSize);
element1.Measure(availableSize);
element1Clone.Measure(availableSize);
return(new Size(100, 100));
},
};
Content = CreateAndInitializeRepeater(
itemsSource: Enumerable.Range(0, 5),
layout: layout,
elementFactory: GetDataTemplate("<Button>Hello</Button>"),
repeater: ref repeater,
scrollViewer: ref scrollViewer);
Content.UpdateLayout();
Verify.IsNotNull(repeater.TryGetElement(0));
Verify.IsNotNull(repeater.TryGetElement(1));
layout.MeasureLayoutFunc = null;
repeater.InvalidateMeasure();
Content.UpdateLayout();
Verify.IsNull(repeater.TryGetElement(0)); // not pinned, should be auto recycled.
Verify.IsNotNull(repeater.TryGetElement(1)); // pinned, should stay alive
});
}