【使用委托】

1. 定义委托和定义委托回调函数。
2. 在构造函数里初始化委托和回调函数。
3. 使用委托。

使用示例

MenuSystemCharacter.h

protected:
    UFUNCTION(BlueprintCallable)
    void CreateGameSession();

    // 第一步A：定义委托回调函数
    void OnCreateSessionComplete(FName SessionName, bool bWasSuccessful);

private:
    // 第一步B：定义委托
    FOnCreateSessionCompleteDelegate CreateSessionCompleteDelegate;

MenuSystemCharacter.cpp

#include "OnlineSubsystem.h"
#include "OnlineSessionSettings.h"

DEFINE_LOG_CATEGORY(LogTemplateCharacter);

//////////////////////////////////////////////////////////////////////////
// AMenuSystemCharacter
// 第二步：初始化委托与回调
AMenuSystemCharacter::AMenuSystemCharacter():
    CreateSessionCompleteDelegate(FOnCreateSessionCompleteDelegate::CreateUObject(this,&AMenuSystemCharacter::OnCreateSessionComplete))
{
    IOnlineSubsystem* OnlineSubsystem = IOnlineSubsystem::Get();
    if (OnlineSubsystem)
    {
        OnlineSessionInterface = OnlineSubsystem->GetSessionInterface();

        if (GEngine)
        {
            GEngine->AddOnScreenDebugMessage(
                -1,
                15.f,
                FColor::Blue,
                FString::Printf(TEXT("Found subsystem %s"), *OnlineSubsystem->GetSubsystemName().ToString())
            );
        }
    }
}


void AMenuSystemCharacter::CreateGameSession()
{
    // 当点击按键1时调用
    if (!OnlineSessionInterface.IsValid())
    {
        return;
    }

    auto ExistingSession = OnlineSessionInterface->GetNamedSession(NAME_GameSession);
    if (ExistingSession != nullptr)
    {
        OnlineSessionInterface->DestroySession(NAME_GameSession);
    }

    // 第三步：使用委托
    OnlineSessionInterface->AddOnCreateSessionCompleteDelegate_Handle(CreateSessionCompleteDelegate);

    TSharedPtr<FOnlineSessionSettings> SessionSettings = MakeShareable(new FOnlineSessionSettings());
    SessionSettings->bIsLANMatch = false;
    SessionSettings->NumPublicConnections = 4;
    SessionSettings->bAllowJoinInProgress = true;
    SessionSettings->bAllowJoinViaPresence = true;
    SessionSettings->bShouldAdvertise = true;
    SessionSettings->bUsesPresence = true;

    const ULocalPlayer* LocalPlayer = GetWorld()->GetFirstLocalPlayerFromController();
    OnlineSessionInterface->CreateSession(*LocalPlayer->GetPreferredUniqueNetId(), NAME_GameSession, *SessionSettings);
}

void AMenuSystemCharacter::OnCreateSessionComplete(FName SessionName, bool bWasSuccessful)
{
    if (bWasSuccessful)
    {
        if (GEngine)
        {
            GEngine->AddOnScreenDebugMessage(
                -1,
                15.f,
                FColor::Blue,
                FString::Printf(TEXT("Created session success::%s"), *SessionName.ToString())
            );
        }
    }
    else 
    {
        if (GEngine) 
        {
            GEngine->AddOnScreenDebugMessage(
                -1,
                15.f,
                FColor::Red,
                FString::Printf(TEXT("Failed to create session"))
            );
        }
    }
}