BlueRoseNote/03-UnrealEngine/Gameplay/Lyra/UE5 Lyra学习笔记(6)—CommonUI.md

---
title: UE5 Lyra学习笔记(6)—CommonUI
date: 2024-03-22 15:03:59
excerpt: 
tags: 
rating: ⭐
---
# 前言
- 全局管理类
	- UGameUIManagerSubsystem：父类为UGameInstanceSubsystem，主要的功能是管理CurrentPolicy(UGameUIPolicy)。
		- UGameUIPolicy：将UPrimaryGameLayout添加到Viewport中。
			- UPrimaryGameLayout
- Widgets
使用[[#GameplayAbility]]检测玩家输入并且开启UI。

# UPrimaryGameLayout
父类为UCommonUserWidget。主要功能为UILayer以及Dormant状态管理。
## UILayer
使用`TMap<FGameplayTag, TObjectPtr<UCommonActivatableWidgetContainerBase>> Layers;`进行多UI层的管理，不同Layer使用GameplayTag进行区分。Lyra的UILayer分为以下4个层：
- UI.Layer.Game
- UI.Layer.GameMenu
- UI.Layer.Menu
- UI.Layer.Modal

```c++
template <typename ActivatableWidgetT = UCommonActivatableWidget>
TSharedPtr<FStreamableHandle> PushWidgetToLayerStackAsync(FGameplayTag LayerName, bool bSuspendInputUntilComplete, TSoftClassPtr<UCommonActivatableWidget> ActivatableWidgetClass, TFunction<void(EAsyncWidgetLayerState, ActivatableWidgetT*)> StateFunc)
{
	static_assert(TIsDerivedFrom<ActivatableWidgetT, UCommonActivatableWidget>::IsDerived, "Only CommonActivatableWidgets can be used here");

	static FName NAME_PushingWidgetToLayer("PushingWidgetToLayer");
	const FName SuspendInputToken = bSuspendInputUntilComplete ? UCommonUIExtensions::SuspendInputForPlayer(GetOwningPlayer(), NAME_PushingWidgetToLayer) : NAME_None;

	FStreamableManager& StreamableManager = UAssetManager::Get().GetStreamableManager();
	TSharedPtr<FStreamableHandle> StreamingHandle = StreamableManager.RequestAsyncLoad(ActivatableWidgetClass.ToSoftObjectPath(), FStreamableDelegate::CreateWeakLambda(this,
		[this, LayerName, ActivatableWidgetClass, StateFunc, SuspendInputToken]()
		{
			UCommonUIExtensions::ResumeInputForPlayer(GetOwningPlayer(), SuspendInputToken);

			ActivatableWidgetT* Widget = PushWidgetToLayerStack<ActivatableWidgetT>(LayerName, ActivatableWidgetClass.Get(), [StateFunc](ActivatableWidgetT& WidgetToInit) {
				StateFunc(EAsyncWidgetLayerState::Initialize, &WidgetToInit);
			});

			StateFunc(EAsyncWidgetLayerState::AfterPush, Widget);
		})
	);

	// Setup a cancel delegate so that we can resume input if this handler is canceled.
	StreamingHandle->BindCancelDelegate(FStreamableDelegate::CreateWeakLambda(this,
		[this, StateFunc, SuspendInputToken]()
		{
			UCommonUIExtensions::ResumeInputForPlayer(GetOwningPlayer(), SuspendInputToken);
			StateFunc(EAsyncWidgetLayerState::Canceled, nullptr);
		})
	);

	return StreamingHandle;
}

template <typename ActivatableWidgetT = UCommonActivatableWidget>
ActivatableWidgetT* PushWidgetToLayerStack(FGameplayTag LayerName, UClass* ActivatableWidgetClass)
{
	return PushWidgetToLayerStack<ActivatableWidgetT>(LayerName, ActivatableWidgetClass, [](ActivatableWidgetT&) {});
}

template <typename ActivatableWidgetT = UCommonActivatableWidget>
ActivatableWidgetT* PushWidgetToLayerStack(FGameplayTag LayerName, UClass* ActivatableWidgetClass, TFunctionRef<void(ActivatableWidgetT&)> InitInstanceFunc)
{
	static_assert(TIsDerivedFrom<ActivatableWidgetT, UCommonActivatableWidget>::IsDerived, "Only CommonActivatableWidgets can be used here");

	if (UCommonActivatableWidgetContainerBase* Layer = GetLayerWidget(LayerName))
	{
		return Layer->AddWidget<ActivatableWidgetT>(ActivatableWidgetClass, InitInstanceFunc);
	}

	return nullptr;
}
```

### RegisterLayer
用于向PrimaryGameLayout注册UILayer。（为了方便管理里面的CommonActivatabbleWidgetStack)
```c++
void RegisterLayer(UPARAM(meta = (Categories = "UI.Layer")) FGameplayTag LayerTag, UCommonActivatableWidgetContainerBase* LayerWidget);
```

Content/UI的W_OverallUILayout调用，它是一个根组件为Overlay，下面有4个子组件(CommonActivatabbleWidgetStack)：
- GameLayer_Stack：游戏内UI，类似HUD。
- GameMenu_Stack：游戏相关的 "菜单"，例如游戏中的库存用户界面。
- Menu_Stack：设置界面等。
- Model_Stack：游戏内的模态确认对话框、错误对话框。
# GameplayAbility
Lyra使用2个位于Plugins/ShooterCore/Content/Input/Abilites/ 
- GAB_ShowWidget_WhenInputPressed
- GAB_ShowWidget_WhileInputHeld

 GAB_ShowWidget_WhenInputPressed：![[GAB_ShowWidget_WhenInputPressed.png|800]]
 GAB_ShowWidget_WhileInputHeld，略微复杂一些会多一些：![[GAB_ShowWidget_WhileInputHeld.png|1200]]

## GameplayTasks
- UCancellableAsyncAction
	- [[#UAsyncAction_PushContentToLayerForPlayer]]

核心函数逻辑如下，主要调用UPrimaryGameLayout::PushWidgetToLayerStackAsync()
```c++
void UAsyncAction_PushContentToLayerForPlayer::Activate()
{
	if (UPrimaryGameLayout* RootLayout = UPrimaryGameLayout::GetPrimaryGameLayout(OwningPlayerPtr.Get()))
	{
		TWeakObjectPtr<UAsyncAction_PushContentToLayerForPlayer> WeakThis = this;
		StreamingHandle = RootLayout->PushWidgetToLayerStackAsync<UCommonActivatableWidget>(LayerName, bSuspendInputUntilComplete, WidgetClass, [this, WeakThis](EAsyncWidgetLayerState State, UCommonActivatableWidget* Widget) {
			if (WeakThis.IsValid())
			{
				switch (State)
				{
					case EAsyncWidgetLayerState::Initialize:
						BeforePush.Broadcast(Widget);
						break;
					case EAsyncWidgetLayerState::AfterPush:
						AfterPush.Broadcast(Widget);
						SetReadyToDestroy();
						break;
					case EAsyncWidgetLayerState::Canceled:
						SetReadyToDestroy();
						break;
				}
			}
			SetReadyToDestroy();
		});
	}
	else
	{
		SetReadyToDestroy();
	}
}
```