遊戲進度存檔

本指南說明如何使用 C++ SDK 中的 Google Play Games 服務快照 API，實作遊戲進度存檔功能。您可以在 PgsSnapshotsClient 中取得 API。

事前準備

取得快照用戶端

如要開始使用快照 API，遊戲必須先取得 PgsSnapshotsClient 控制代碼。要取得此物件，您可以呼叫 PgsSnapshotsClient_create() 方法，然後在 Android Activity 內傳遞。

注意：C++ SDK 函式會透過回呼以非同步方式傳回結果。

// Assuming 'android_activity' is a jobject referencing your Android Activity
PgsSnapshotsClient* snapshots_client = PgsSnapshotsClient_create(android_activity);

// ... use the client ...

// When done, destroy the client to free resources
// PgsSnapshotsClient_destroy(snapshots_client);

顯示遊戲進度存檔

您可以在遊戲的任何位置整合加入快照 API，讓玩家可以選擇儲存或還原進度。 為簡化開發作業，快照 API 提供預設的遊戲進度存檔選擇使用者介面 (UI)。如要啟動這個 UI，請呼叫 PgsSnapshotsClient_showSelectSnapshotUI。

// Callback function to handle the result of showing the UI
void OnShowSavedGamesUI(PgsStatusCode status_code, void* user_data) {
  if (status_code == PGS_STATUS_SUCCESS) {
    // UI was shown successfully. The player can now interact with it.
    // The game doesn't receive direct data back from this callback about
    // which snapshot was selected. Your game should typically provide options
    // to load or open snapshots by name after the UI is dismissed.
  } else {
    // Handle error or failure to show UI
  }
}

// Function to show the default Saved Games UI
void ShowSavedGamesUI(PgsSnapshotsClient* client, jobject activity) {
  const char* title = "See My Saves";
  bool allow_add_button = true;
  bool allow_delete_button = true;
  int max_snapshots = 5;

  PgsSnapshotsClient_showSelectSnapshotUI(
      client,
      activity,
      title,
      allow_add_button,
      allow_delete_button,
      max_snapshots,
      OnShowSavedGamesUI,
      NULL // user_data
  );
}

// Example usage:
// ShowSavedGamesUI(snapshots_client, android_activity);

寫入遊戲進度存檔

在遊戲進度存檔中儲存內容：

  1. 使用 PgsSnapshotsClient_open() 以非同步方式開啟快照。 如要建立新儲存項目，請將 create_if_not_found 指定為 true。
  2. 結果會顯示在 PgsSnapshotsClient_OpenCallback 中。如果成功且沒有衝突，您會收到 PgsSnapshot*。
  3. 準備要儲存的資料，並以位元組陣列 (uint8_t*) 形式表示。
  4. 建立 PgsSnapshotMetadataChange* 物件來描述儲存作業。

  5. 呼叫 PgsSnapshotsClient_commitAndClose，將變更傳送至 Google 的伺服器。

    // Callback for commitAndClose
void OnSnapshotCommitted(PgsStatusCode status_code, PgsSnapshotMetadata* metadata, void* user_data) {
    if (status_code == PGS_STATUS_SUCCESS) {
    // Save successful
    if (metadata) {
    // Metadata for the committed snapshot
    PgsSnapshotMetadata_Release(metadata);
  }
} else {
    // Handle error
  }
}

// Function to write data to a snapshot
void WriteSnapshot(PgsSnapshotsClient* client, PgsSnapshot* snapshot,
               const uint8_t* data, size_t data_size,
               const char* description /*, Bitmap coverImage */) {

PgsSnapshotMetadataChange* metadataChange = NULL; // Placeholder

  // Commit the operation
  PgsSnapshotsClient_commitAndClose(
      client,
      snapshot,
      metadataChange,
      data,
      data_size,
      OnSnapshotCommitted,
      NULL // user_data
  );

  // if (metadataChange) PgsSnapshotMetadataChange_Release(metadataChange);
}

// Callback for opening the snapshot before writing
void OnSnapshotOpenForWrite(PgsStatusCode status_code,
                        PgsSnapshot* snapshot,
                        PgsSnapshotConflict* conflict,
                        void* user_data) {
  if (status_code == PGS_STATUS_SUCCESS) {
    if (snapshot) {
      // Successfully opened/created. Now write to it.
     const char* save_data_str = "MY_GAME_SAVE_DATA";
     const uint8_t* data = (const uint8_t*)save_data_str;
     size_t data_size = strlen(save_data_str);

      WriteSnapshot((PgsSnapshotsClient*)user_data, snapshot, data, data_size, "My Save Description");
      // PgsSnapshot_destroy(snapshot) is likely called after commitAndClose by the SDK
    } else if (conflict) {
      // Handle conflict before writing, or open with a policy that auto-resolves.
      PgsSnapshotConflict_destroy(conflict);
    }
  } else {
    // Handle error opening
  }
}

// Example: Open and write to a snapshot
void OpenAndWriteExample(PgsSnapshotsClient* client, const char* snapshot_name) {
PgsSnapshotsClient_open(
  client,
  snapshot_name,
  true, // create_if_not_found
  kPgsSnapshotConflictPolicyManual, // Or another policy
  OnSnapshotOpenForWrite,
  client // user_data
);
}

載入遊戲進度存檔

如要擷取遊戲進度存檔，請按照下列步驟操作：

  1. 使用 PgsSnapshotsClient_open()，以非同步方式依名稱開啟快照。

  2. 在 PgsSnapshotsClient_OpenCallback 中，如果成功，請存取資料。API 提供取得 uint8_t* 資料和大小的方法，但本文未詳細說明從 PgsSnapshot 或相關聯的 PgsSnapshotContents 讀取位元組的方法。

    // Assuming functions exist to read data from PgsSnapshotContents
// For example, PgsSnapshotContents* PgsSnapshot_getContents(PgsSnapshot* snapshot);
// For example, bool PgsSnapshotContents_readFully(PgsSnapshotContents* contents, uint8_t** out_data, size_t* out_size);
// For example, void PgsSnapshotContents_releaseData(uint8_t* data);

void OnSnapshotOpenForRead(PgsStatusCode status_code,
                       PgsSnapshot* snapshot,
                       PgsSnapshotConflict* conflict,
                       void* user_data) {
    if (status_code == PGS_STATUS_SUCCESS) {
    if (snapshot) {
    // Successfully opened. Now read from it.
    // THE FOLLOWING IS HYPOTHETICAL based on common patterns:
    // PgsSnapshotContents* contents = PgsSnapshot_getContents(snapshot);
    // uint8_t* data = NULL;
    // size_t data_size = 0;
    // if (contents && PgsSnapshotContents_readFully(contents, &data, &data_size)) {
    //   // Successfully read data
    //   Log("Snapshot data loaded, size: %zu", data_size);
    //   ... process data ...
    //   PgsSnapshotContents_releaseData(data);
    // }
    // PgsSnapshotContents_destroy(contents); // If necessary
      PgsSnapshot_destroy(snapshot);
    } else if (conflict) {
      // Handle conflict
      Log("Snapshot open resulted in a conflict.");
      PgsSnapshotConflict_destroy(conflict);
    }
  } else {
    // Handle error opening
    Log("Error while opening Snapshot: %d", status_code);
  }
}

// Example: Load a specific saved game
void LoadSnapshotByName(PgsSnapshotsClient* client, const char* snapshot_name) {
  int conflictResolutionPolicy = kPgsSnapshotConflictPolicyMostRecentlyModified;

  PgsSnapshotsClient_open(
      client,
      snapshot_name,
      false, // create_if_not_found
      conflictResolutionPolicy,
      OnSnapshotOpenForRead,
      NULL // user_data
  );
}

處理遊戲進度存檔衝突

呼叫 PgsSnapshotsClient_open 回呼時，如果 conflict 參數不是 NULL，則發生衝突，請使用 PgsSnapshotsClient_resolveConflict 解決衝突。

/// @brief Asynchronously resolves a snapshot conflict.
///
/// @param snapshots_client The client handle.
/// @param conflict_id The ID of the conflict to resolve.
/// @param snapshot_id The ID of the snapshot to use for resolution.
/// @param metadata_change The metadata changes to apply to the snapshot, or
/// NULL for no changes.
/// @param contents The contents to resolve the conflict with.
/// @param callback Function to be called with result of asynchronous
/// operation. See PgsSnapshotsClient_OpenCallback.
/// @param user_data Arbitrary data pointer to be passed back to callback.
void PgsSnapshotsClient_resolveConflict(
    PgsSnapshotsClient* snapshots_client,
    const char* conflict_id,
    const char* snapshot_id,
    PgsSnapshotMetadataChange* metadata_change,
    PgsSnapshotContents* contents,
    PgsSnapshotsClient_OpenCallback callback,
    void* user_data);