11

Runtime/RecyclerView/Adapter/ItemRender.cs

@@ -13,25 +13,28 @@ namespace AlicizaX.UI
         void Unbind();
     }
 
+    internal interface IItemRenderInitializer
+    {
+        void Reset(ViewHolder viewHolder);
+    }
+
     public abstract class ItemRender<TData, THolder> : IItemRender
+        , IItemRenderInitializer
         where THolder : ViewHolder
     {
         private Action defaultClickAction;
-
-        protected ItemRender(THolder holder)
-        {
-            Holder = holder ?? throw new ArgumentNullException(nameof(holder));
-            CurrentIndex = -1;
-        }
-
-        protected THolder Holder { get; }
+        protected THolder Holder { get; private set; }
 
         protected TData CurrentData { get; private set; }
 
-        protected int CurrentIndex { get; private set; }
+        protected int CurrentIndex { get; private set; } = -1;
+
+        protected bool IsSelected { get; private set; }
 
         public void Bind(object data, int index, Action defaultClickAction)
         {
+            EnsureHolder();
+
             if (data is not TData itemData)
             {
                 throw new InvalidCastException(
@@ -47,20 +50,22 @@ namespace AlicizaX.UI
 
         public void UpdateSelection(bool selected)
         {
+            EnsureHolder();
+            IsSelected = selected;
             OnSelectionChanged(selected);
         }
 
         public void Unbind()
         {
-            OnClear();
-            CurrentData = default;
-            CurrentIndex = -1;
-            defaultClickAction = null;
-            Holder.ClearInteractionCallbacks();
+            ResetState();
         }
 
         protected abstract void Bind(TData data, int index);
 
+        protected virtual void OnHolderChanged()
+        {
+        }
+
         protected virtual void OnSelectionChanged(bool selected)
         {
         }
@@ -96,19 +101,63 @@ namespace AlicizaX.UI
         {
             OnPointerExit();
         }
+
+        void IItemRenderInitializer.Reset(ViewHolder viewHolder)
+        {
+            if (viewHolder == null)
+            {
+                throw new ArgumentNullException(nameof(viewHolder));
+            }
+
+            if (viewHolder is not THolder holder)
+            {
+                throw new InvalidOperationException(
+                    $"RecyclerView item render '{GetType().FullName}' expects holder '{typeof(THolder).FullName}', but got '{viewHolder.GetType().FullName}'.");
+            }
+
+            ResetState();
+            Holder = holder;
+            OnHolderChanged();
+        }
+
+        private void EnsureHolder()
+        {
+            if (Holder == null)
+            {
+                throw new InvalidOperationException(
+                    $"RecyclerView item render '{GetType().FullName}' has not been initialized with a holder.");
+            }
+        }
+
+        private void ResetState()
+        {
+            if (Holder != null)
+            {
+                if (IsSelected)
+                {
+                    IsSelected = false;
+                    OnSelectionChanged(false);
+                }
+
+                OnClear();
+                Holder.ClearInteractionCallbacks();
+            }
+
+            CurrentData = default;
+            CurrentIndex = -1;
+            IsSelected = false;
+            defaultClickAction = null;
+        }
     }
 
     internal static class ItemRenderResolver
     {
         internal sealed class ItemRenderDefinition
         {
-            private readonly ConstructorInfo constructor;
-
-            public ItemRenderDefinition(Type itemRenderType, Type holderType, ConstructorInfo constructor)
+            public ItemRenderDefinition(Type itemRenderType, Type holderType)
             {
                 ItemRenderType = itemRenderType;
                 HolderType = holderType;
-                this.constructor = constructor;
             }
 
             public Type ItemRenderType { get; }
@@ -128,7 +177,20 @@ namespace AlicizaX.UI
                         $"RecyclerView item render '{ItemRenderType.FullName}' expects holder '{HolderType.FullName}', but got '{viewHolder.GetType().FullName}'.");
                 }
 
-                return (IItemRender)constructor.Invoke(new object[] { viewHolder });
+                if (Activator.CreateInstance(ItemRenderType, true) is not IItemRender itemRender)
+                {
+                    throw new InvalidOperationException(
+                        $"RecyclerView item render '{ItemRenderType.FullName}' could not be created.");
+                }
+
+                if (itemRender is not IItemRenderInitializer initializer)
+                {
+                    throw new InvalidOperationException(
+                        $"RecyclerView item render '{ItemRenderType.FullName}' must inherit from ItemRender<TData, THolder>.");
+                }
+
+                initializer.Reset(viewHolder);
+                return itemRender;
             }
         }
 
@@ -171,16 +233,16 @@ namespace AlicizaX.UI
             ConstructorInfo constructor = itemRenderType.GetConstructor(
                 BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic,
                 null,
-                new[] { holderType },
+                Type.EmptyTypes,
                 null);
 
             if (constructor == null)
             {
                 throw new InvalidOperationException(
-                    $"RecyclerView item render '{itemRenderType.FullName}' must declare a constructor with a single '{holderType.FullName}' parameter.");
+                    $"RecyclerView item render '{itemRenderType.FullName}' must have a parameterless constructor.");
             }
 
-            return new ItemRenderDefinition(itemRenderType, holderType, constructor);
+            return new ItemRenderDefinition(itemRenderType, holderType);
         }
 
         private static bool TryGetHolderType(Type itemRenderType, out Type holderType)