123 lines
5.4 KiB
Markdown
123 lines
5.4 KiB
Markdown
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# BindWidgetAnim
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- **功能描述：** 指定在C++类中该UWidgetAnimation属性一定要绑定到UMG下的某个动画
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- **使用位置：** UPROPERTY
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- **引擎模块：** Widget Property
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- **元数据类型：** bool
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- **限制类型：** UWidget子类里UWidgetAnimation属性
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- **关联项：** [BindWidgetAnimOptional](../BindWidgetAnimOptional/BindWidgetAnimOptional.md)
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- **常用程度：** ★★★★★
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指定在C++类中该UWidgetAnimation属性一定要绑定到UMG下的某个动画。
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作用同BindWidget类似，都是用来把C++的属性和BP里的控件或动画赋值绑定起来。但又有一些区别：
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- UWidgetAnimation和Widget不同，Widget的属性和控件只要同名就可以自动绑定起来，而UWidgetAnimation就不允许不加BindWidgetAnim而同名，否则会名字冲突报错。这是由于UMG里创建的Widget默认是不创建BP变量的，子控件只是WidgetTree下的一个对象，但是动画是默认会创建BP变量的。因此即使是UMG里先定义动画，然后C++里再定义同名属性，也是会过不了编译的。
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- UWidgetAnimation属性必须得是Transient，否则也会报错。我想这是因为UWidgetAnimation自然会在BP里作为子对象序列化，而不需要在C++序列的时候访问到该属性，因此强制Transient以免不小心序列化它。另外UWidgetAnimation只是用作表现，因此其实也会自动的加上CPF_RepSkip，跳过网络复制。
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## 测试代码：
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```cpp
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UCLASS(BlueprintType)
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class INSIDER_API UMyProperty_BindWidget :public UUserWidget
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{
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GENERATED_BODY()
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UMyProperty_BindWidget(const FObjectInitializer& ObjectInitializer);
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public:
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UPROPERTY(EditAnywhere, BlueprintReadWrite)
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class UWidgetAnimation* MyAnimation_NotFound;
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//UPROPERTY(EditAnywhere, BlueprintReadWrite)
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//class UWidgetAnimation* MyAnimation_SameName;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Transient, meta = (BindWidgetAnim))
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class UWidgetAnimation* MyAnimation_Bind;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Transient, meta = (BindWidgetAnimOptional))
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class UWidgetAnimation* MyAnimation_BindOptional;
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};
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```
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## 测试效果：
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测试过程和BindWidget类似，在C++和UMG中定义不同类型属性和动画对象。可以根据VS里实际对象的值发现：
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- MyAnimation_Bind和MyAnimation_BindOptional都自动的绑定了正确的动画对象。
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- 没有加BindWidgetAnim的MyAnimation_SameName必须注释掉，否则会和UMG里的MyAnimation_SameName名字冲突。
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- 再提一下，不能像Widget里一样先UMG里定义动画，然后再C++定义同名属性，因为WidgetAnimation是一定会创建BP变量的，这是关键不同。
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## 原理：
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大致逻辑和BindWidget类似，都是判断属性是否BindWidgetAnim。然后相应的在编译和改名的时候判断。
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关于动画变量设置PropertyFlags的逻辑在CreateClassVariablesFromBlueprint里，可以看见加上了4个属性，明确了不要序列化该属性。
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而为UWidgetAnimation*属性自动绑定赋值的逻辑在BindAnimationsStatic，一眼就懂。
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```cpp
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bool FWidgetBlueprintEditorUtils::IsBindWidgetAnimProperty(const FProperty* InProperty, bool& bIsOptional)
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{
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if (InProperty)
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{
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bool bIsBindWidgetAnim = InProperty->HasMetaData("BindWidgetAnim") || InProperty->HasMetaData("BindWidgetAnimOptional");
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bIsOptional = InProperty->HasMetaData("BindWidgetAnimOptional");
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return bIsBindWidgetAnim;
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}
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return false;
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}
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void FWidgetBlueprintCompilerContext::CreateClassVariablesFromBlueprint()
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{
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for (UWidgetAnimation* Animation : WidgetBP->Animations)
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{
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FEdGraphPinType WidgetPinType(UEdGraphSchema_K2::PC_Object, NAME_None, Animation->GetClass(), EPinContainerType::None, true, FEdGraphTerminalType());
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FProperty* AnimationProperty = CreateVariable(Animation->GetFName(), WidgetPinType);
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if ( AnimationProperty != nullptr )
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{
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const FString DisplayName = Animation->GetDisplayName().ToString();
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AnimationProperty->SetMetaData(TEXT("DisplayName"), *DisplayName);
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AnimationProperty->SetMetaData(TEXT("Category"), TEXT("Animations"));
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AnimationProperty->SetPropertyFlags(CPF_Transient);
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AnimationProperty->SetPropertyFlags(CPF_BlueprintVisible);
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AnimationProperty->SetPropertyFlags(CPF_BlueprintReadOnly);
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AnimationProperty->SetPropertyFlags(CPF_RepSkip);
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WidgetAnimToMemberVariableMap.Add(Animation, AnimationProperty);
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}
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}
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}
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void FWidgetBlueprintCompilerContext::FinishCompilingClass(UClass* Class)
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{
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if (!WidgetAnimProperty->HasAnyPropertyFlags(CPF_Transient))
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{
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const FText BindWidgetAnimTransientError = LOCTEXT("BindWidgetAnimTransient", "The property @@ uses BindWidgetAnim, but isn't Transient!");
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MessageLog.Error(*BindWidgetAnimTransientError.ToString(), WidgetAnimProperty);
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}
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}
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void UWidgetBlueprintGeneratedClass::BindAnimationsStatic(UUserWidget* Instance, const TArrayView<UWidgetAnimation*> InAnimations, const TMap<FName, FObjectPropertyBase*>& InPropertyMap)
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{
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// Note: It's not safe to assume here that the UserWidget class type is a UWidgetBlueprintGeneratedClass!
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// - @see InitializeWidgetStatic()
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for (UWidgetAnimation* Animation : InAnimations)
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{
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if (Animation->GetMovieScene())
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{
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// Find property with the same name as the animation and assign the animation to it.
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if (FObjectPropertyBase*const* PropPtr = InPropertyMap.Find(Animation->GetMovieScene()->GetFName()))
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{
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check(*PropPtr);
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(*PropPtr)->SetObjectPropertyValue_InContainer(Instance, Animation);
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}
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}
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}
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}
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```
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