Sweet Snippet 之 PlayerPrefs for UE4

喜欢ヅ旅行 2022-09-05 11:24 323阅读 0赞

> 在 Unity 中进行本地存储,我们一般会用到 PlayerPrefs,而在 UE4 中,我们一般会使用 USaveGame,不过 USaveGame 在使用上和 PlayerPrefs 相差较大,这里给出一个 UE4 的 PlayerPrefs 实现,原理上仅是对 USaveGame 做了进一步的封装

*  首先我们继承 USaveGame 创建 UPlayerPrefsSaveGame 类型

#include "CoreMinimal.h"
    #include "GameFramework/SaveGame.h"
    #include "PlayerPrefsSaveGame.generated.h"
    
    class PlayerPrefs;
    
    UCLASS()
    class UPlayerPrefsSaveGame : public USaveGame
    {
    	GENERATED_BODY()
    
    protected:
    	UPROPERTY()
        TMap<FString, int> IntMap;
    	
    	UPROPERTY()
        TMap<FString, float> FloatMap;
    
    	UPROPERTY()
    	TMap<FString, FString> StringMap;
    
    	friend class PlayerPrefs;
    };

*  接着就是 PlayerPrefs 类型了,提供了和 Unity 中 PlayerPrefs 基本一致的接口

#include "CoreMinimal.h"
    #include "PlayerPrefsSaveGame.h"
    
    class PlayerPrefs
    {
    public:
    	void Init();
    	void Release();
    	void Update(float DeltaTime);
    
    	// removes all key values from the preferences
    	void DeleteAll();
        // removes key from the preferences, if key does not exist, DeleteKey has no impact
    	void DeleteKey(const FString& Key);
    	// returns the value corresponding to key in the preference file if it exists
    	float GetFloat(const FString& Key, float Default = 0);
    	// returns the value corresponding to key in the preference file if it exists
    	int GetInt(const FString& Key, int Default = 0);
    	// returns the value corresponding to key in the preference file if it exists
    	FString GetString(const FString& Key, const FString& Default = TEXT(""));
    	// returns the value corresponding to key in the preference file if it exists
    	bool GetBool(const FString& Key, bool Default = false);
    	// returns true if the given key exists in preference, otherwise returns false
    	bool HasKey(const FString& Key);
    	// writes all modified preferences to disk
    	void Save();
    	// sets the float value of the preference identified by the given key
    	void SetFloat(const FString& Key, float Value);
    	// sets a single integer value for the preference identified by the given key
    	void SetInt(const FString& Key, int Value);
    	// sets a single string value for the preference identified by the given key
    	void SetString(const FString& Key, const FString& Value);
    	// sets a single bool value for the preference identified by the given key
    	void SetBool(const FString& Key, bool Value);
    
    private:
    	UPlayerPrefsSaveGame* mPlayerPrefsSaveGame{ nullptr };
    	bool mPlayerPrefsDirty{ false };
    	float mPlayerPrefsUpdateTime{ 0 };
    	float mPlayerPrefsUpdateInterval{ 5 };
    };

值得提到的一点是 PlayerPrefs 主动存储的实现方式,代码中除了释放 PlayerPrefs 时会做一次主动存储以外,另外还使用了一个脏标记(mPlayerPrefsDirty)来定时的检查是否要进行主动存储

#include "PlayerPrefs.h"
    #include "Kismet/GameplayStatics.h"
    
    namespace 
    {
    	FString PlayerPrefsSaveGameSlotName = TEXT("PlayerPrefs");
    }
    
    void PlayerPrefs::Init()
    {
    	check(!mPlayerPrefsSaveGame);
    
    	auto SavedGame = UGameplayStatics::LoadGameFromSlot(PlayerPrefsSaveGameSlotName, 0);
    	mPlayerPrefsSaveGame = Cast<UPlayerPrefsSaveGame>(SavedGame);
    
    	if (!mPlayerPrefsSaveGame)
    	{
    		mPlayerPrefsSaveGame = Cast<UPlayerPrefsSaveGame>(UGameplayStatics::CreateSaveGameObject(UPlayerPrefsSaveGame::StaticClass()));
    		bool Saved = UGameplayStatics::SaveGameToSlot(mPlayerPrefsSaveGame, PlayerPrefsSaveGameSlotName, 0);
    		if (!Saved)
    		{
    			UE_LOG(LogTemp, Error, TEXT("[PlayerPrefs]Error to save PlayerPrefs ..."));
    			return;
    		}
    	}
    
    	if (!mPlayerPrefsSaveGame)
    	{
    		UE_LOG(LogTemp, Error, TEXT("[PlayerPrefs]Error to init PlayerPrefs ..."));
    		return;
    	}
    
    	// add GC reference
    	mPlayerPrefsSaveGame->AddToRoot();
    }
    
    void PlayerPrefs::Release()
    {
    	Save();
    
    	if (mPlayerPrefsSaveGame)
    	{
    		// remove GC reference
    		mPlayerPrefsSaveGame->RemoveFromRoot();
    	}
    
    	mPlayerPrefsSaveGame = nullptr;
    }
    
    void PlayerPrefs::Update(float DeltaTime)
    {
    	mPlayerPrefsUpdateTime += DeltaTime;
    	if (mPlayerPrefsUpdateTime >= mPlayerPrefsUpdateInterval)
    	{
    		mPlayerPrefsUpdateTime = 0;
    		if (mPlayerPrefsDirty)
    		{
    			Save();
    		}
    	}
    }
    
    // removes all key values from the preferences
    void PlayerPrefs::DeleteAll()
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		mPlayerPrefsSaveGame->IntMap.Empty();
    		mPlayerPrefsSaveGame->FloatMap.Empty();
    		mPlayerPrefsSaveGame->StringMap.Empty();
    		mPlayerPrefsDirty = true;
    	}
    }
    
    // removes key from the preferences, if key does not exist, DeleteKey has no impact
    void PlayerPrefs::DeleteKey(const FString& Key)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		bool Ret = mPlayerPrefsSaveGame->IntMap.Remove(Key) > 0;
    		Ret |= mPlayerPrefsSaveGame->FloatMap.Remove(Key) > 0;
    		Ret |= mPlayerPrefsSaveGame->StringMap.Remove(Key) > 0;
    		
    		if (Ret)
    		{
    			mPlayerPrefsDirty = true;
    		}
    	}
    }
    
    // returns the value corresponding to key in the preference file if it exists
    float PlayerPrefs::GetFloat(const FString& Key, float Default)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->FloatMap.Contains(Key))
    		{
    			return mPlayerPrefsSaveGame->FloatMap[Key];
    		}
    	}
    
    	return Default;
    }
    
    // returns the value corresponding to key in the preference file if it exists
    int PlayerPrefs::GetInt(const FString& Key, int Default)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->IntMap.Contains(Key))
    		{
    			return mPlayerPrefsSaveGame->IntMap[Key];
    		}
    	}
    
    	return Default;
    }
    
    // returns the value corresponding to key in the preference file if it exists
    FString PlayerPrefs::GetString(const FString& Key, const FString& Default)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->StringMap.Contains(Key))
    		{
    			return mPlayerPrefsSaveGame->StringMap[Key];
    		}
    	}
    
    	return Default;
    }
    
    // returns the value corresponding to key in the preference file if it exists
    bool PlayerPrefs::GetBool(const FString& Key, bool Default)
    {
    	auto DefaultInt = Default ? 1 : 0;
    	auto Value = GetInt(Key, DefaultInt);
    	return Value > 0;
    }
    
    // returns true if the given key exists in preference, otherwise returns false
    bool PlayerPrefs::HasKey(const FString& Key)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		bool Ret = mPlayerPrefsSaveGame->IntMap.Contains(Key) ||
    		           mPlayerPrefsSaveGame->FloatMap.Contains(Key) ||
    		           mPlayerPrefsSaveGame->StringMap.Contains(Key);
    	    
    		return Ret;
    	}
    
    	return false;
    }
    
    // writes all modified preferences to disk
    void PlayerPrefs::Save()
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		bool Saved = UGameplayStatics::SaveGameToSlot(mPlayerPrefsSaveGame, PlayerPrefsSaveGameSlotName, 0);
    		if (!Saved)
    		{
    			UE_LOG(LogTemp, Error, TEXT("[PlayerPrefs]Error to save PlayerPrefs ..."));
    		}
    		
    		mPlayerPrefsDirty = false;
    	}
    }
    
    // sets the float value of the preference identified by the given key
    void PlayerPrefs::SetFloat(const FString& Key, float Value)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->FloatMap.Contains(Key))
    		{
    			mPlayerPrefsSaveGame->FloatMap[Key] = Value;
    		}
    		else
    		{
    			mPlayerPrefsSaveGame->FloatMap.Add(Key, Value);
    		}
    
    		mPlayerPrefsDirty = true;
    	}
    }
    
    // sets a single integer value for the preference identified by the given key
    void PlayerPrefs::SetInt(const FString& Key, int Value)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->IntMap.Contains(Key))
    		{
    			mPlayerPrefsSaveGame->IntMap[Key] = Value;
    		}
    		else
    		{
    			mPlayerPrefsSaveGame->IntMap.Add(Key, Value);
    		}
    
    		mPlayerPrefsDirty = true;
    	}
    }
    
    // sets a single string value for the preference identified by the given key
    void PlayerPrefs::SetString(const FString& Key, const FString& Value)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->StringMap.Contains(Key))
    		{
    			mPlayerPrefsSaveGame->StringMap[Key] = Value;
    		}
    		else
    		{
    			mPlayerPrefsSaveGame->StringMap.Add(Key, Value);
    		}
    
    		mPlayerPrefsDirty = true;
    	}
    }
    
    // sets a single bool value for the preference identified by the given key
    void PlayerPrefs::SetBool(const FString& Key, bool Value)
    {
    	if (mPlayerPrefsSaveGame)
    	{
    		if (mPlayerPrefsSaveGame->IntMap.Contains(Key))
    		{
    			mPlayerPrefsSaveGame->IntMap[Key] = Value ? 1 : 0;
    		}
    		else
    		{
    			mPlayerPrefsSaveGame->IntMap.Add(Key, Value ? 1 : 0);
    		}
    
    		mPlayerPrefsDirty = true;
    	}
    }

值得注意的一点是,虽然实现上使用了不同类型的映射表(TMap)来存储不同类型的数值,但程序概念上表键(Key)是相通的,不同映射表之间不存在重复的表键(Key)