自定义 StackPanel Prism 区域适配器以支持订购

Question

我有以下用于 StackPanel 的 RegionAdapter 实现，但我需要对与区域关联的项目进行严格排序，谁能帮忙？

我希望将自己注册到区域的视图能够控制那里的位置，也许是某种索引号

    protected override void Adapt(IRegion region, StackPanel regionTarget)
    {
        region.Views.CollectionChanged += (sender, e) =>
        {
            switch (e.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    foreach (FrameworkElement element in e.NewItems)
                    {
                        regionTarget.Children.Add(element);
                    }

                    break;

                case NotifyCollectionChangedAction.Remove:
                    foreach (UIElement elementLoopVariable in e.OldItems)
                    {
                        var element = elementLoopVariable;
                        if (regionTarget.Children.Contains(element))
                        {
                            regionTarget.Children.Remove(element);
                        }
                    }

                    break;
            }
        };
    }

Answer 1

如何解决这个问题很大程度上取决于排序是指 (a) 视图的类型还是 (b) 视图的实例。如果您只想指定例如ViewA 类型的视图应该在ViewB 类型的视图之上，则属于前者。如果您想指定如何对同一视图类型的多个具体实例进行排序，则属于后者。

A.按类型排序

On 选项是实现一个自定义属性，例如OrderIndexAttribute，它公开一个整数属性：

[AttributeUsage(AttributeTargets.Class, AllowMultiple = false)]
public OrderIndexAttribute : Attribute
{
    public int Index { get; }

    public OrderIndexAttribute(int index)
    {
        Index = index;
    }
}

使用该属性标记您的视图类：

[OrderIndex(2)]
public ViewA : UserControl
{...}

将视图添加到区域时获取类型的属性：

case NotifyCollectionChangedAction.Add:
    foreach (FrameworkElement element in e.NewItems)
    {
        // Get index for view
        var viewType = element.GetType();
        var viewIndex= viewType.GetCustomAttribute<OrderIndexAttribute>().Index;
        // This method needs to iterate through the views in the region and determine
        // where a view with the specified index needs to be inserted
        var insertionIndex = GetInsertionIndex(viewIndex);
        regionTarget.Children.Insert(insertionIndex, element);
    }
    break;

B.按实例排序

让你的视图实现一个接口：

public interface ISortedView 
{
   int Index { get; }
}

在将视图添加到区域时，尝试将插入的视图投射到界面，读取索引，然后执行与上述相同的操作：

case NotifyCollectionChangedAction.Add:
    foreach (FrameworkElement element in e.NewItems)
    {
        // Get index for view
        var sortedView = element as ISortedView;
        if (sortedView != null)
        {
            var viewIndex = sortedView.Index;
            // This method needs to iterate through the views in the region and determine
            // where a view with the specified index needs to be inserted
            var insertionIndex = GetInsertionIndex(viewIndex);
            regionTarget.Children.Insert(insertionIndex, sortedView);
        }
        else
        { // Add at the end of the StackPanel or reject adding the view to the region }
    }

Answer 2

我发现 Marc 的“A. Sort type wise”案例对我的情况非常有帮助。我需要使用 OrderIndexAttribute 将视图分类到区域中，如果视图实际上没有 OrderIndexAttribute，我仍然可以添加视图。

正如您将在下面看到的，我通过跟踪列表中的视图索​​引来做到这一点。没有该属性的视图的插入索引默认为零，以便它排序到 StackPanel 的前面（或顶部）。

这篇原始帖子相当古老，但也许有人会像我一样偶然发现它，并且会发现我的贡献很有帮助。欢迎提出重构建议。 :-)

public class StackPanelRegionAdapter : RegionAdapterBase<StackPanel>
{
    private readonly List<int> _indexList;

    public StackPanelRegionAdapter(IRegionBehaviorFactory behaviorFactory)
        : base(behaviorFactory)
    {
        _indexList = new List<int>();
    }

    protected override void Adapt(IRegion region, StackPanel regionTarget)
    {
        
        region.Views.CollectionChanged += (sender, e) =>
        {
            switch (e.Action)
            {
                case NotifyCollectionChangedAction.Add:
                    foreach (FrameworkElement element in e.NewItems)
                    {
                        var viewType = element.GetType();

                        // Get the custom attributes for this view, if any
                        var customAttributes = viewType.GetCustomAttributes(false);

                        var viewIndex = 0;  // Default the viewIndex to zero

                        // Determine if the view has the OrderIndexAttribute.
                        // If it does have the OrderIndexAttribute, get its sort index.
                        if (HasThisAttribute(customAttributes))
                        {
                            viewIndex= viewType.GetCustomAttribute<OrderIndexAttribute>().Index;
                        }
                        
                        // Get the insertion index
                        var insertionIndex = GetInsertionIndex(viewIndex);

                        regionTarget.Children.Insert(insertionIndex, element);
                    }
                    break;

                case NotifyCollectionChangedAction.Remove:
                    foreach (UIElement elementLoopVariable in e.OldItems)
                    {
                        var element = elementLoopVariable;
                        if (regionTarget.Children.Contains(element))
                        {
                            regionTarget.Children.Remove(element);
                        }
                    }
                    break;
            }
        };
    }

    private static bool HasThisAttribute(IReadOnlyList<object> customAttributes)
    {
        // Determine if the view has the OrderIndexAttribute
        if (customAttributes.Count == 0) return false;
        for (var i = 0; i < customAttributes.Count; i++)
        {
            var name = customAttributes[i].GetType().Name;
            if (name == "OrderIndexAttribute") return true;
        }

        return false;
    }

    private int GetInsertionIndex(in int viewIndex)
    {
        // Add the viewIndex to the index list if not already there
        if (_indexList.Contains(viewIndex) == false)
        {
            _indexList.Add(viewIndex);
            _indexList.Sort();
        }

        // Return the list index of the viewIndex
        for (var i = 0; i < _indexList.Count; i++)
        {
            if (_indexList[i].Equals(viewIndex))
            {
                return i;
            }
        }

        return 0;
    }

    protected override IRegion CreateRegion()
    {
        return new AllActiveRegion();
    }
}

Answer 3

Marc 和 R.Evans 的回答帮助我创建了自己的更多通用 RegionAdapter，并进行了以下改进：

• 使用ViewSortHint 兼容Prism 6
• Prism 7 / .Net 5 兼容
• 在多个适配器中使用的助手类
• 更少的代码

适配方法：

    protected override void Adapt(IRegion region, StackPanel regionTarget)
    {
        region.Views.CollectionChanged += (s, e) =>
        {
            if (e.Action == NotifyCollectionChangedAction.Add)
                foreach (FrameworkElement item in e.NewItems)
                {
                    regionTarget.Children.Insert(regionTarget.Children.GetInsertionIndex(item), item);
                }
            else if (e.Action == NotifyCollectionChangedAction.Remove)
                foreach (UIElement item in e.OldItems)
                {
                    if (regionTarget.Children.Contains(item))
                    {
                        regionTarget.Children.Remove(item);
                    }
                }
        };
    }

助手/扩展：

internal static int GetInsertionIndex(this IList items, in object newItem)
    {
        // Return the list index of the viewIndex
        foreach (object item in items)
        {
            var currentIndex = item.GetType().GetCustomAttribute<ViewSortHintAttribute>()?.Hint ?? "0";
            var intendedIndex = newItem.GetType().GetCustomAttribute<ViewSortHintAttribute>()?.Hint ?? "0";

            if (currentIndex.CompareTo(intendedIndex) >= 0)
                return items.IndexOf(item);
        }

        // if no greater index is found, insert the item at the end
        return items.Count;
    }