关于UE4动态资源加载(蓝图类)

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需要注意的几点：

1.调试环境下进行的资源加载方式到打包出来后不一定能够使用。

2.假如遇到调试模式下程序运行正常，但是打包出来后程序crash，可以查看log： Saved/Logs/filename/log

3.资源路径的代码书写格式 

map : "Game/Maps/Main.map"

蓝图类 :  "Game/Blueprint/Skill/skill_1.skill_1_C"

正常的uasset: "Game/Bluerpint/Sound/sound_1.sound_1"

关于资源路径的技巧

1>关于蓝图类的加载记得在结尾要加 _C  就比如 FString sPath = "/Game/Blueprints/Actor/RuntimeActor/RuntimeCameraBP.RuntimeCameraBP_C";
2>使用UE4编辑器的Copy Reference即可，除了蓝图类要加 _C 其他的资源应该都可以加载，就比如 FString sPath = "Texture2D'/Game/Blueprints/UITextures/风险挂接-选中.风险挂接-选中'";

CopyReference操作如下图， 粘贴出来就是 StaticMesh'/Game/Geometry/Meshes/TemplateFloor.TemplateFloor'。然后我们就可以拿到这个路径去进行Load。

关于动态资源生成的几种方式

资源加载远不止我列出这几种方式，会有更多。

1>代码方式如何Spawn蓝图类？

//SpawnActor用法
FString sPath = "/Game/Blueprints/Actor/RuntimeActor/RuntimeCameraBP.RuntimeCameraBP_C";

FVector vDir = GGameInstance->Player->GetActorForwardVector();
//vDir.Z = 0;
FVector vLocation = GGameInstance->Player->GetActorLocation() + vDir * 1000;
FActorSpawnParameters params;
params.SpawnCollisionHandlingOverride = ESpawnActorCollisionHandlingMethod::AdjustIfPossibleButAlwaysSpawn;
UObject* pObject = UUtilsLibrary::CreateAsset(sPath);
UBlueprintGeneratedClass* BP = Cast(pObject);
	
auto pActor = GWorld->SpawnActor(BP, FTransform(vLocation), params);

2>另外一种代码Spawn蓝图类的方式

不再写资源路径，让资源去蓝图中选择。TSubclassOf这种写法，可以在蓝图中选择你的这个指定<>类型的蓝图类，比如下面我的例子就是继承自ASPPivotMeshActor的蓝图类可以被选中

/** Pivot Actor bp calss, in the blueprint set value. */
UPROPERTY(Category = "Dynamic Data (General Settings)", EditAnywhere, BlueprintReadWrite)
TSubclassOf PivotActorBP;

//How to Spawn?
SPPivotMeshActor = GWorld->SpawnActor(PivotActorBP, FTransform(CenterPosition));

3>通过构造加载方式1

如何非构造函数方式加载一个uasset(直接代码写中文以及中文图片的命名方式的习惯不好，不要学我)

//静态方法, 加载uasset的资源，比如UI贴图等。建议写到继承自UBlueprintFunctionLibrary的类中
UFUNCTION(BlueprintCallable, Category = "Utils")
static UObject* CreateAsset(const FString& AssetPath);

//实现
UObject* UUtilsLibrary::CreateAsset(const FString& AssetPath)
{
	FStringAssetReference ref = AssetPath;
	UObject* uoTmp = ref.ResolveObject();
	if (uoTmp == nullptr)
	{
		UE_LOG(LogTemp, Log, TEXT("CreateAsset path = %s"), *AssetPath);
		FStreamableManager& EKAssetLoader = GGameInstance->GetStreamableManager();
		uoTmp = EKAssetLoader.LoadSynchronous(ref, true);
	}

	return uoTmp;
}

//使用案例1， 为UMG上面的UButton和UImage设置图片(直接代码写中文以及中文图片的命名方式的习惯不好，不要学我)
//UButton dynamic change normal image
UObject* pHovered_ContentAttach = UUtilsLibrary::CreateAsset(TEXT("Texture2D'/Game/Blueprints/UITextures/风险挂接-选中.风险挂接-选中'"));
Button_BottomType_Mode->WidgetStyle.Normal.SetResourceObject(pHovered_ContentAttach);

//UImage dynamic change normal image
FString sImagePath = TEXT("Texture2D'/Game/Blueprints/UITextures/添加摄像头.添加摄像头'");
UObject* pImage = UUtilsLibrary::CreateAsset(sImagePath);
RETURN_IF_NULL(pImage);
Image_CameraAdd->Brush.SetResourceObject(pImage);



//使用案例2， 结合CreateAsset在代码中创建一个UMG蓝图

// 对于ScrollBox……等类似列表容器可先使用该种方式, 创建然后再做添加
UFUNCTION()
UUserWidget* CreateFromAsset(const FStringAssetReference& StringRef, ESPPreviewType emUIType, bool bAddToViewPort, int32 nZorder = 0);

//实现
UUserWidget* USPUIManager::CreateFromAsset(const FStringAssetReference& StringRef, ESPPreviewType emUIType, bool bAddToViewPort, int32 nZorder)
{
	UUserWidget* pUI = nullptr;
	UObject* inObject = UUtilsLibrary::CreateAsset(StringRef.ToString());
	if (inObject)
	{
		pUI = CreateWidget(GGameInstance, Cast(inObject));
		if (pUI)
		{
			if (bAddToViewPort)
			{
				pUI->AddToViewport(nZorder);
				m_WidgetCache.Add(pUI);
			}

			if (Cast(pUI))
			{
				Cast(pUI)->PreviewTypeArray.Add(emUIType);
			}
		}
	}

	return pUI;
}

//HowTo Use Sample
UUserWidget* pUW = GGameInstance->UIManager()->CreateFromAsset(StringRef, emUIType, false);
if(pUW) UGridSlot* pGSlot = SPGridPanel_Left->AddChildToGrid(pUW, row, column);

4>通过构造加载方式2

// set default pawn class to our Blueprinted character 构造函数中加载
static ConstructorHelpers::FClassFinder PlayerPawnBPClass(TEXT("/Game/ThirdPersonCPP/Blueprints/ThirdPersonCharacter"));
if (PlayerPawnBPClass.Class != NULL)
{
	DefaultPawnClass = PlayerPawnBPClass.Class;
}

5>通过构造加载方式3 LoadClass以及ConstructorHelpers::FClassFinder

//.h中声明一下 加载一个蓝图类
UPROPERTY()
TSubclassOf BP_1;

//构造函数中实现, 加载一个蓝图类
BP_1 = LoadClass(NULL, TEXT("Blueprint'/Game/BP/MeshBP_1.MeshBP_C'"));


//.h中声明一下 加载一个UMG
UPROPERTY()
TSubclassOf UIMain;

//构造函数中实现, 加载一个UMG, 这里可以注意并没有写_C
static ConstructorHelpers::FClassFinder MYWidget(TEXT("/Game/UMG/UI_Main"));
UIMain_Instance = MYWidget.Class;

6>通过构造函数内Load资源 进行资源加载  LoadObject

// 红.h中声明一下
UPROPERTY()
UMaterialInstance* MaterialInstance_Level1;


// Sets default values 构造函数中通过LoadObject加载
UWorldActorsManager::UWorldActorsManager()
	: m_pSelectedActor(nullptr)
{
	mapMaterials.Reset();

	/*MaterialInstance_Level1 = LoadObject(NULL, TEXT("/Game/Material/ColorMatreial_Inst_1.ColorMatreial_Inst_1"), NULL, LOAD_None, NULL);
	MaterialInstance_Level2 = LoadObject(NULL, TEXT("/Game/Material/ColorMatreial_Inst_2.ColorMatreial_Inst_2"), NULL, LOAD_None, NULL);
	MaterialInstance_Level3 = LoadObject(NULL, TEXT("/Game/Material/ColorMatreial_Inst_3.ColorMatreial_Inst_3"), NULL, LOAD_None, NULL);
	MaterialInstance_Level4 = LoadObject(NULL, TEXT("/Game/Material/ColorMatreial_Inst_4.ColorMatreial_Inst_4"), NULL, LOAD_None, NULL);*/
}

7>如何加载一张磁盘上的Png、jpg、jpeg、bmp到UMG上

//如何加载一张磁盘上的Png、jpg、jpeg、bmp到UMG上 头文件
UFUNCTION(BlueprintCallable, Category = "Utils")
static UTexture2D* LoadTexture(FString fullPath);

//具体实现
UTexture2D* UUtilsLibrary::LoadTexture(FString fullPath)
{
	RETURN_NULL_IF_FALSE(FPaths::FileExists(fullPath));

	TArray RawFileData;
	UTexture2D* MyTexture = NULL;
	RETURN_NULL_IF_FALSE(FFileHelper::LoadFileToArray(RawFileData, *fullPath));
	IImageWrapperModule& ImageWrapperModule = FModuleManager::LoadModuleChecked(FName("ImageWrapper"));
	// Note: PNG format.
	EImageFormat format = EImageFormat::Invalid;
	if (fullPath.EndsWith(TEXT(".png")))
	{
		format = EImageFormat::PNG;
	}
	else if (fullPath.EndsWith(TEXT(".jpg")) || fullPath.EndsWith(TEXT(".jpeg")))
	{
		format = EImageFormat::JPEG;
	}
	else if (fullPath.EndsWith(TEXT(".bmp")))
	{
		format = EImageFormat::BMP;
	}
	TSharedPtr ImageWrapper = ImageWrapperModule.CreateImageWrapper(format);
	RETURN_NULL_IF_FALSE(ImageWrapper.IsValid());
	RETURN_NULL_IF_FALSE(ImageWrapper->SetCompressed(RawFileData.GetData(), RawFileData.Num()));
	TArray UncompressedBGRA;
	RETURN_NULL_IF_FALSE(ImageWrapper->GetRaw(ERGBFormat::BGRA, 8, UncompressedBGRA));

	// Create the UTexture for rendering
	UTexture2D* result = UTexture2D::CreateTransient(ImageWrapper->GetWidth(), ImageWrapper->GetHeight(), PF_B8G8R8A8);

	// Fill in the source data from the file
	void* TextureData = result->PlatformData->Mips[0].BulkData.Lock(LOCK_READ_WRITE);
	FMemory::Memcpy(TextureData, UncompressedBGRA.GetData(), UncompressedBGRA.Num());
	result->PlatformData->Mips[0].BulkData.Unlock();

	// Update the rendering resource from data.
	result->UpdateResource();

	return result;

}

//使用案例 注意是Full路径，绝对路径
UTexture2D* pTexture2D = UUtilsLibrary::LoadTexture(m_pRuntimeHotPoint->GetObjInfo()->GetBindMoviePath() + TEXT(".jpg"));

如有错误还请纠正。

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