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 preferencesvoid DeleteAll();// removes key from the preferences, if key does not exist, DeleteKey has no impactvoid DeleteKey(const FString& Key);// returns the value corresponding to key in the preference file if it existsfloat GetFloat(const FString& Key, float Default = 0);// returns the value corresponding to key in the preference file if it existsint GetInt(const FString& Key, int Default = 0);// returns the value corresponding to key in the preference file if it existsFString GetString(const FString& Key, const FString& Default = TEXT(""));// returns the value corresponding to key in the preference file if it existsbool GetBool(const FString& Key, bool Default = false);// returns true if the given key exists in preference, otherwise returns falsebool HasKey(const FString& Key);// writes all modified preferences to diskvoid Save();// sets the float value of the preference identified by the given keyvoid SetFloat(const FString& Key, float Value);// sets a single integer value for the preference identified by the given keyvoid SetInt(const FString& Key, int Value);// sets a single string value for the preference identified by the given keyvoid SetString(const FString& Key, const FString& Value);// sets a single bool value for the preference identified by the given keyvoid 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 referencemPlayerPrefsSaveGame->AddToRoot();
}void PlayerPrefs::Release()
{Save();if (mPlayerPrefsSaveGame){// remove GC referencemPlayerPrefsSaveGame->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)