81 lines
2.3 KiB
Markdown
81 lines
2.3 KiB
Markdown
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# DisplayThumbnail
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- **功能描述：** 指定是否在该属性左侧显示一个缩略图。
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- **使用位置：** UPROPERTY
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- **引擎模块：** Object Property
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- **元数据类型：** bool
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- **限制类型：** UObject*
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- **关联项：** [ThumbnailSize](../ThumbnailSize.md)
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- **常用程度：** ★★★
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指定是否在该属性左侧显示一个缩略图。
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## 测试代码：
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```cpp
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UCLASS(Blueprintable, BlueprintType)
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class INSIDER_API AMyActor_Thumbnail_Test :public AActor
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{
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GENERATED_BODY()
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public:
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UPROPERTY(EditAnywhere, BlueprintReadWrite, meta = (DisplayThumbnail = "false"))
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UObject* MyObject;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, meta = (DisplayThumbnail = "true"))
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UObject* MyObject_DisplayThumbnail;
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UPROPERTY(EditAnywhere, BlueprintReadWrite)
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AActor* MyActor;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, meta = (DisplayThumbnail = "true"))
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AActor* MyActor_DisplayThumbnail;
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};
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```
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## 测试效果：
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可见MyObject_DisplayThumbnail的左侧显示出了所选择资产的缩略图，而MyObject因为设置了false因此是没有的。如果不设置DisplayThumbnail =false，则默认也是会显示缩略图的。
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MyActor_DisplayThumbnail出现了缩略图的图标，但是发现并没有显示出正确的说了图。AActor在默认情况下是不显示缩略图的。
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## 原理：
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判断是否要显示缩略图就在这个函数。
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默认情况下非Actor类型才会显示。另外SPropertyEditorAsset是用在资产类型属性上的，其实就是Object属性。
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```cpp
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bool SPropertyEditorAsset::ShouldDisplayThumbnail(const FArguments& InArgs, const UClass* InObjectClass) const
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{
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if (!InArgs._DisplayThumbnail || !InArgs._ThumbnailPool.IsValid())
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{
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return false;
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}
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bool bShowThumbnail = InObjectClass == nullptr || !InObjectClass->IsChildOf(AActor::StaticClass());
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// also check metadata for thumbnail & text display
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const FProperty* PropertyToCheck = nullptr;
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if (PropertyEditor.IsValid())
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{
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PropertyToCheck = PropertyEditor->GetProperty();
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}
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else if (PropertyHandle.IsValid())
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{
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PropertyToCheck = PropertyHandle->GetProperty();
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}
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if (PropertyToCheck != nullptr)
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{
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PropertyToCheck = GetActualMetadataProperty(PropertyToCheck);
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return GetTagOrBoolMetadata(PropertyToCheck, TEXT("DisplayThumbnail"), bShowThumbnail);
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}
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return bShowThumbnail;
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}
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```
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