Unreal Engine 4 C++ Slate 介绍——用C++和Slate创建菜单（三）
Unreal Engine 4 C Slate 介绍用C和Slate创建菜单三第一步概述和准备第二步绑定数据第三步有用的数据
Unreal Engine 4 C++ Slate 介绍——用C++和Slate创建菜单（三）
好记性不如烂笔头啊，还是记录一下!
欢迎回到我的使用Slate和C++在虚幻引擎4中创建菜单的教程系列！
第一步：概述和准备
什么是数据绑定？ 数据绑定是一种来自软件开发的概念，其中信息输出（例如玩家的当前血量）与实际展示的信息相关联。这样，只要更改数据（例如，对玩家造成伤害），显示就会自动更新。
在我们的示例中，我们将创建一个新的Slate UI，用作游戏中的HUD，在屏幕的上角显示玩家的当前血量和得分。最初，HUD将只有静态值 - 我们将在下一步中将其更改为绑定数据。 我将粘贴下面的代码，但不会详细介绍它是如何工作的 - 这是所有很简单的内容，已经在过去的教程中已经讲过了。
TutorialGameHUDUI.h
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.// TutorialGameHUDUI.h - Provides an implementation of the Slate UI representing the tutorial game HUD.#pragma once#include "Slate.h"// Lays out and controls the Tutorial HUD UI.class STutorialGameHUDUI : public SCompoundWidget{ SLATE_BEGIN_ARGS(STutorialGameHUDUI) : _OwnerHUD() { } SLATE_ARGUMENT(TWeakObjectPtr<class ATutorialGameHUD>, OwnerHUD); SLATE_END_ARGS()public: /** * Constructs and lays out the Tutorial HUD UI Widget. * * \args Arguments structure that contains widget-specific setup information. **/void Construct(const FArguments& args);private: /** * Stores a weak reference to the HUD owning this widget. **/ TWeakObjectPtr<class ATutorialGameHUD> OwnerHUD; /** * A reference to the Slate Style used for this HUD's widgets. **/conststruct FGlobalStyle* HUDStyle;};
TutorialGameHUDUI.cpp
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.#include "SlateTutorials.h"#include "TutorialGameHUD.h"#include "TutorialGameHUDUI.h"#include "Menus/GlobalMenuStyle.h"#include "Menus/MenuStyles.h"void STutorialGameHUDUI::Construct(const FArguments& args){ OwnerHUD = args._OwnerHUD; HUDStyle = &FMenuStyles::Get().GetWidgetStyle<FGlobalStyle>("Global"); ChildSlot [ SNew(SOverlay) + SOverlay::Slot() .HAlign(HAlign_Right) .VAlign(VAlign_Top) [ SNew(STextBlock) .TextStyle(&HUDStyle->MenuTitleStyle) .Text(FText::FromString("SCORE: 0")) ] + SOverlay::Slot() .HAlign(HAlign_Left) .VAlign(VAlign_Top) [ SNew(STextBlock) .TextStyle(&HUDStyle->MenuTitleStyle) .Text(FText::FromString("HEALTH: 100")) ] ];}
TutorialGameHUD.h
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.// TutorialGameHUD.h - Provides an implementation of the HUD that will embed the Tutorial Game UI.#pragma once#include "GameFramework/HUD.h"#include "TutorialGameHUD.generated.h"/** * Provides an implementation of the game's in-game HUD, which will display the player's current health and score. **/UCLASS()class ATutorialGameHUD : public AHUD{ GENERATED_UCLASS_BODY()public: /** * Initializes the Slate UI and adds it as a widget to the game viewport. **/virtualvoid PostInitializeComponents() override;private: /** * Reference to the Game HUD UI. **/ TSharedPtr<class STutorialGameHUDUI> GameHUD;};
TutorialGameHUD.cpp
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.#include "SlateTutorials.h"#include "TutorialGameHUD.h"#include "TutorialGameHUDUI.h"ATutorialGameHUD::ATutorialGameHUD(constclass FPostConstructInitializeProperties& PCIP) : Super(PCIP){}void ATutorialGameHUD::PostInitializeComponents(){ Super::PostInitializeComponents(); if (GEngine && GEngine->GameViewport) { UGameViewportClient* Viewport = GEngine->GameViewport; SAssignNew(GameHUD, STutorialGameHUDUI) .OwnerHUD(TWeakObjectPtr<ATutorialGameHUD>(this)); Viewport->AddViewportWidgetContent( SNew(SWeakWidget).PossiblyNullContent(GameHUD.ToSharedRef()) ); }}继续构建项目并设置一个新的地图和游戏模式，并让HUD显示出来！
第二步：绑定数据
我们有两个信息需要显示，我们想绑定到我们的UI：得分和血量。这两个都是整数，但它们必须绑定为我们的HUD的字符串！我们很快会从游戏模式（积分）和角色（血量）获取此信息，但首先我们将处理数据绑定部分。我们的绑定将有两个重要的任务：第一，它将获取实际数据。接下来，它会将其转换为要应用于文本块控件的FText。
他们都需要两个东西：属性和绑定它的东西。在我们的例子中，因为我们需要对数据进行额外的处理（从一个整数转换为一个字符串），我们将在我们的widget类本身有一个函数来绑定。 将以下私有属性值和方法添加到STutorialGameHUDUI类中：
TutorialGameHUDUI.h
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.// TutorialGameHUDUI.h - Provides an implementation of the Slate UI representing the tutorial game HUD.#pragma once#include "Slate.h"// Lays out and controls the Tutorial HUD UI.class STutorialGameHUDUI : public SCompoundWidget{ SLATE_BEGIN_ARGS(STutorialGameHUDUI) : _OwnerHUD() { } SLATE_ARGUMENT(TWeakObjectPtr<class ATutorialGameHUD>, OwnerHUD); SLATE_END_ARGS()public: /** * Constructs and lays out the Tutorial HUD UI Widget. * * \args Arguments structure that contains widget-specific setup information. **/void Construct(const FArguments& args);private: /** * Stores a weak reference to the HUD owning this widget. **/ TWeakObjectPtr<class ATutorialGameHUD> OwnerHUD; /** * A reference to the Slate Style used for this HUD's widgets. **/conststruct FGlobalStyle* HUDStyle;private: /** * Attribute storing the binding for the player's score. **/ TAttribute<FText> Score; /** * Attribute storing the binding for the player's health. **/ TAttribute<FText> Health; /** * Our Score will be bound to this function, which will retrieve the appropriate data and convert it into an FText. **/ FText GetScore() const; /** * Our Health will be bound to this function, which will retrieve the appropriate data and convert it into an FText. **/ FText GetHealth() const; };在虚幻中使用TAttribute类型来提供有一个accessor/getter的数据绑定。 接下来，我们有两个常量函数，负责检索和格式化数据到UI可以使用的类型！那么我们如何实际做绑定？ 好吧，它很简单 - 事实上，如果你在C++中为Unreal项目完成了输入绑定，你已经做到了。 在STutorialGameHUDUI的Construct方法的顶部，在捕获HUDStyle之后，添加以下内容将我们的TAttributes绑定到它们适当的函数：
Score.Bind(this, &STutorialGameHUDUI::GetScore);Health.Bind(this, &STutorialGameHUDUI::GetHealth);接下来，我们在UI布局中直接使用TAttributes类型：
+ SOverlay::Slot() .HAlign(HAlign_Right) .VAlign(VAlign_Top) [ SNew(STextBlock) .TextStyle(&HUDStyle->MenuTitleStyle) .Text(Score) ]+ SOverlay::Slot() .HAlign(HAlign_Left) .VAlign(VAlign_Top) [ SNew(STextBlock) .TextStyle(&HUDStyle->MenuTitleStyle) .Text(Health) ]最后，我们要在绑定函数放入一些临时数据，只是为了确保一切正常工作：
FText STutorialGameHUDUI::GetScore() const { return FText::FromString("SCORE: --"); }FText STutorialGameHUDUI::GetHealth() const { return FText::FromString("HEALTH: --"); }继续编译肯定一切正常，恭喜你！你刚刚绑定了你的文本块！ 您可以对Slate的所有内容执行此绑定 - 按钮文本，列表项，图像背景，样式等。
https://d26ilriwvtzlb.cloudfront.net/4/47/%D0%A1%D0%BA%D1%80%D0%B8%D0%BD%D1%88%D0%BE%D1%82_2015-03-18_16.55.25.png
第三步：有用的数据
如果你只需要学习如何做数据绑定，而不关心本教程的细节，那么你可以跳过本节 - 在这里，我们只是实现了分数和血量功能。
为了获得本教程的得分和血量数据，我添加了以下GameMode和Character类，并将它们设置为与GameMap关卡一起使用。
TutGameMode.h
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.// TutGameMode.h - Provides a simple game mode providing a Score!#pragma once#include "GameFramework/GameMode.h"#include "TutGameMode.generated.h"/** * A simple game mode providing a means of retrieving and adjusting a single Score value. **/UCLASS()class ATutGameMode : public AGameMode{ GENERATED_UCLASS_BODY()public: /** * Retrieves the current Score from the game mode. **/ UFUNCTION(BlueprintPure, BlueprintCallable, Category = "Score") int32 GetScore(); /** * Adds to the game score. **/ UFUNCTION(BlueprintCallable, Category = "Score") void AddPoints(int32 value); /** * Removes from the game score. **/ UFUNCTION(BlueprintCallable, Category = "Score") void DeductPoints(int32 value);private: /** * Stores the current score. **/ int32 CurrentScore;};
TutGameMode.cpp
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.#include "SlateTutorials.h"#include <algorithm>#include "TutGameMode.h"ATutGameMode::ATutGameMode(constclass FPostConstructInitializeProperties& PCIP) : Super(PCIP), CurrentScore(0){}int32 ATutGameMode::GetScore(){ return CurrentScore;}void ATutGameMode::AddPoints(int32 value){ if (value > 0) CurrentScore += value;}void ATutGameMode::DeductPoints(int32 value){ if (value > 0) CurrentScore = std::max(CurrentScore - value, 0);}
TutorialCharacter.h
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.// TutorialCharacter.h - Provides a simple character providing Health!#pragma once#include "GameFramework/Character.h"#include "TutorialCharacter.generated.h"/** * A simple character providing a means of retrieving and manipulating health. **/UCLASS()class ATutorialCharacter : public ACharacter{ GENERATED_UCLASS_BODY()public: /** * Stores the character's current health. **/ UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "Combat") int32 Health;};
TutorialCharacter.cpp
// Copyright 1998-2015 Epic Games, Inc. All Rights Reserved.#include "SlateTutorials.h"#include "TutorialCharacter.h"ATutorialCharacter::ATutorialCharacter(constclass FPostConstructInitializeProperties& PCIP) : Super(PCIP){ Health = 100;}一旦我们有了这些，更新得分和血量的数据是很简单的；
TutorialGameHUDUI.cpp
FText STutorialGameHUDUI::GetScore() const{ // NOTE: THIS IS A TERRIBLE WAY TO DO THIS. DO NOT DO IT. IT ONLY WORKS ON SERVERS. USE GAME STATES INSTEAD! ATutGameMode* gameMode = Cast<ATutGameMode>(OwnerHUD->GetWorldSettings()->GetWorld()->GetAuthGameMode()); if (gameMode == nullptr) return FText::FromString(TEXT("SCORE: --")); FString score = TEXT("SCORE: "); score.AppendInt(gameMode->GetScore()); return FText::FromString(score);}FText STutorialGameHUDUI::GetHealth() const { ATutorialCharacter* character = Cast<ATutorialCharacter>(OwnerHUD->PlayerOwner->GetCharacter()); if (character == nullptr) return FText::FromString(TEXT("HEALTH: --")); FString health = TEXT("HEALTH: "); health.AppendInt(character->Health); return FText::FromString(health);}继续并运行游戏，然后更新得分！（您可以在示例文件中通过按Home/End来调整血量，然后按Page Up/Page Down来调整分数）。示例文件下载地址：File:SlateTutorials-3.zip
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