UE5 - 制作游戏中切换窗口后游戏自动暂停功能

个人学习笔记归档；

玩家在游戏运行时，比如在窗口模式下，当切换到其它程序的窗口，游戏自动暂停的逻辑，需要借助C++的基类来实现，方法为以下步骤；

添加C++类必须在UE中添加，这样新的C++类才能保证环境配置正确：

新的类继承GameViewportClient：

设置好路径和类名即可：

然后直接打开VS：

把建立的MyGameViewportClient.h内容修改为：

// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "Engine/GameViewportClient.h"
#include "MyGameViewportClient.generated.h"

DECLARE_DYNAMIC_MULTICAST_DELEGATE(FOnWindowFocusChanged);

/**
 * 
 */
UCLASS()
class TESTCODEPROJECT_API UMyGameViewportClient : public UGameViewportClient
{
    GENERATED_BODY()
    
    public:
    UPROPERTY(BlueprintAssignable, Category = "Window Focus")
    FOnWindowFocusChanged OnWindowLostFocus;

    UPROPERTY(BlueprintAssignable, Category = "Window Focus")
    FOnWindowFocusChanged OnWindowReceivedFocus;

    UFUNCTION(BlueprintPure, Category = "Window Focus")
    static UMyGameViewportClient* GetMyGameViewportClient();

protected:
    virtual void LostFocus(FViewport* InViewport) override;
    virtual void ReceivedFocus(FViewport* InViewport) override;

};

把MyGameViewportClient.cpp内容修改为：

// Fill out your copyright notice in the Description page of Project Settings.

#include "System/MyGameViewportClient.h"
#include "Engine/Engine.h"

void UMyGameViewportClient::LostFocus(FViewport* InViewport)
{
    Super::LostFocus(InViewport);
    OnWindowLostFocus.Broadcast();
}

void UMyGameViewportClient::ReceivedFocus(FViewport* InViewport)
{
    Super::ReceivedFocus(InViewport);
    OnWindowReceivedFocus.Broadcast();
}

UMyGameViewportClient* UMyGameViewportClient::GetMyGameViewportClient()
{
    if (GEngine && GEngine->GameViewport)
    {
        // 获取引擎当前的 Viewport 并转换成我们自己的类
        return Cast<UMyGameViewportClient>(GEngine->GameViewport);
    }
    return nullptr;
}

保存源码后编译，注意只用关注仅生成列表中是否有错误：

这样就可以通过获取My Game Viewport Client绑定相关事件，在游戏运行时，比如在窗口模式下，当玩家切换到其它程序的窗口，游戏自动暂停等逻辑：

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