[游戏开发]UE4 TreeView-＞ExpandAll无法展开所有层级问题

在UMG中继承了UserObjectListEntry，代码通过Cast<IUserObjectListEntry>(&Widget)转换失败，查看源码后发现还有个UUserObjectListEntry。

IInterface是在C++中使用，而UInterface是封装了Interface，因为蓝图对接口的支持不太行具体原因没有深入研究。

实现原理：在OnEntryWidgetGenerated后手动展开当前节点

// Fill out your copyright notice in the Description page of Project Settings.


#include "Widget/TreeViewEx.h"


UTreeViewEx::UTreeViewEx(const FObjectInitializer& ObjectInitializer)
	: Super(ObjectInitializer)
{
	OnEntryWidgetGenerated().AddUObject(this, &UTreeViewEx::InitAllChildren);
}


void UTreeViewEx::InitAllChildren(UUserWidget& Widget)
{
	TSubclassOf<UUserObjectListEntry> UserObjectListEntry = UUserObjectListEntry::StaticClass();
	//直接Cast会失败，因为蓝图使用的接口是通过UInterface实现的
	if (IUserObjectListEntry* Entry = Cast<IUserObjectListEntry>(&Widget))
	{
		SetItemExpansion(Entry->GetListItem(), true);
	}
	else if (Widget.GetClass()->ImplementsInterface(UserObjectListEntry))
	{
		TScriptInterface<IUserObjectListEntry> MyInterface;
		MyInterface.SetObject(&Widget);
		if (MyInterface.GetObject())
		{
			auto ListItem = UUserObjectListEntryLibrary::GetListItemObject(MyInterface);
			SetItemExpansion(ListItem, true);
		}
	}
}

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "Components/TreeView.h"
#include "TreeViewEx.generated.h"

/**
 *
 */
UCLASS()
class XXX_API UTreeViewEx : public UTreeView
{
	GENERATED_BODY()
public:
	UTreeViewEx(const FObjectInitializer& ObjectInitializer);

private:
	void InitAllChildren(UUserWidget& Widget);
};