199 lines
5.4 KiB
Markdown
199 lines
5.4 KiB
Markdown
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---
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title: Slate学习笔记（一）：Slate动态控制与其他技巧
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date: 2021-02-19 9:22:10
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tags: Slate
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rating: ⭐️
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---
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## 前言
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最近在写MessageBox控件，想兼容UMG与c++中调用Slate。略有心得，遂有此文。
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## 动态Slate
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首先Slate控件树中创建占位用的NullWidget并使用.Expose()绑定Slot指针，使得可以进行后续操作。
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```c++
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ChildSlot
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.VAlign(VAlign_Fill)
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.HAlign(HAlign_Fill)
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[
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SNew(SOverlay)
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+ SOverlay::Slot()
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.HAlign(HAlign_Center)
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.VAlign(VAlign_Center)
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.Expose(UseMenuSlot) // Expose it to a pointer so we can change the widget at runtime
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[
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SNullWidget::NullWidget
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]
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];
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```
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之后就可以通过函数对Slot进行操作了，下面演示如何动态添加或者删除Button：
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```c++
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UseMenuSlot->AttachWidget(
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InText.Get().IsEmpty() ?
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SNullWidget::NullWidget
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:
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SNew(SButton)
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.VAlign(VAlign_Center)
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.HAlign(HAlign_Center)
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[
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SNew(STextBlock)
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]
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);
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```
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### 支持Expose()的容器
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常用的：
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SHorizontalBox
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SVerticalBox
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SOverlay
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其他还有若干也支持的
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## 设置指定长度的Widget
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有的时候需要让控件保持指定的大小，使用SBox的WidthOverride与HeightOverride即可。其他的控件都不支持这2个属性。
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```c++
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ChildSlot
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[
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SNew(SBox)
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.WidthOverride(256)
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.HeightOverride(100)
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[
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SNew(SButton)
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]
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];
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```
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## 指定大小控件的UMG与Slate兼容问题
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UMG的根节点是一个CanvasPanel(UCanvasPanelSlot)。我认为直接给控件加一个SBox来控制大小的方式不太好。这会使得在UMG中的调整大小变得麻烦。所以我的方法是：使用c++调用Slate控件时，在外面再套一层SConstraintCanvas。
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UCanvasPanelSlot本质上是SConstraintCanvas。UMG编辑器中显示的Size实际上是Offset。所以想要指定大小就需要设置Offset的Right与Bottom。
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```c++
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CurrentWidget = SNew(SConstraintCanvas)
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+ SConstraintCanvas::Slot()
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.Anchors(0.5)
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.Alignment(FVector2D(0.5,0.5))
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.Offset(FMargin(0,0,500,400))
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[
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SNew(SCustomWidget)
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];
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GetGameInstance()->GetGameViewportClient()->AddViewportWidgetContent(CurrentWidget.ToSharedRef());
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```
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## c++获取UMG控件
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```c++
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UPROPERTY(Meta = (BindWidget)) //直接获取蓝图中的按钮1
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UButton* ButtonOne;
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```
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```c++
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bool UFWAffectWidget::Initialize()
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{
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if (!Super::Initialize()) return false;
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//方法1
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RootPanel = Cast<UCanvasPanel>(GetRootWidget()); //获取根控件
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if (RootPanel)
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{
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BGImage = Cast<UImage>(RootPanel->GetChildAt(0)); //下标1的BGImage控件
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}
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//方法2
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UButton* ButtonTwo = (UButton*)GetWidgetFromName(TEXT("ButtonTwo"));
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//绑定按钮事件方法1：
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ButtonOne->OnClicked.__Internal_AddDynamic(this,&UFWAffectWidget::ButtonOneEvent,FName("ButtonOneEvent"));
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//绑定事件方法2：委托FScriptDelegate
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FScriptDelegate ButTwoDel;
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ButTwoDel.BindUFunction(this, "ButtonTwoEvent");
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ButtonTwo->OnReleased.Add(ButTwoDel);
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return true;
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}
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```
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参考文章：https://blog.csdn.net/weixin_44200074/article/details/109100521
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## 从UMG控件中获取Slate
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```c++
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TSharedRef<SWidget> UWidget::TakeWidget()
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```
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## 反射
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### 遍历UProperty
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```c++
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for(TFiledIterator<UProperty> It(/*UClass**/)；It;++It)
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{
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UProperty *newProperty=It;
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}
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```
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### 根据名称寻找UProperty
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```c++
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UProperty *foundProperty = FindField<UProperty>(/*UClass**/,TEXT("PropertyName"));
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```
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### Get/Set UProperty
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```c++
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//根据PropertyPath获取属性值
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FCachedPropertyPath PropertyPath(FString(TEXT("PropertyName")));
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T Value;
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ProperthPathHelpers::GetPropertyValue(Object,PropertyPath,Value);
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//有获取就有设置
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ProperthPathHelpers::SetPropertyValue(Object,PropertyPath,Value);
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//还可以获取成String
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FString PropertyValueStr;
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ProperthPathHelpers::GetPropertyValueAsString(Object,PropertyPath,PropertyValueStr);
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//同样，反向也可以
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ProperthPathHelpers::SetPropertyValueFromString(Object,PropertyPath,PropertyValueStr);
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//实际上，我们平时在UE引擎中复制粘贴属性值就是将属性值获取为String以及从String这只属性值的整个过程。
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```
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引用文章：https://zhuanlan.zhihu.com/p/121006155
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更多反射技巧：https://bebylon.dev/ue4guide/engine-programming/uobject-reflection/uobject-reflection/
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## SCompoundWidget、SPanel、SLeafWidget的区别
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### SCompoundWidget
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SCompoundWidget对应于UMG中的“WidgetBlueprint（控件蓝图）”，用来作为控件容器。当我们在C++类向导中创建Slate类时，创建的就是SCompoundWidget。
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可以通过成员ChildSlot结合重载的[]操作符往控件里面添加其他控件
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```c++
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void SStandardSlateWidget::Construct(const FArguments& InArgs)
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{
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ChildSlot
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[
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SNew(STextBlock)
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.Font(FSlateFontInfo("Veranda", 100))
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.Text(NSLOCTEXT("HelloSlate", "HelloSlateText", "Hello, Slate!"))
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];
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}
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```
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### SPanel
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即为SPanel子布局的属性，包括Padding、Size、Horizontal Align、Vertical Align。
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使用Slot添加子控件可以使用“+ Slot()”，也可以调用AddSlot函数，还是以教程1中的SStandardSlateWidget为例
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```c++
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void SStandardSlateWidget::Construct(const FArguments& InArgs)
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{
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ChildSlot
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[
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SAssignNew(VerticalBoxPtr, SVerticalBox)
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+ SVerticalBox::Slot()
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.Padding(1.0)
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.FillHeight(0.3f)
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.HAlign(HAlign_Fill)
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.VAlign(VAlign_Top)
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[
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SNew(SButton)
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]
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+ SVerticalBox::Slot()
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.FillHeight(0.5f)
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.HAlign(HAlign_Center)
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[
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SNew(SButton)
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]
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];
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VerticalBoxPtr->AddSlot()
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.FillHeight(0.2f)
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[
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SNew(SButton)
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];
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}
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```
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### SLeafWidget
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叶子控件，故名思意，该控件不能添加子控件。常用的为STextBlock与SImage。
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