コード例 #1
0
        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
            });
        }