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Clarify AssetManager usage

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PiperOrigin-RevId: 487935478
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MediaPipe Team 2022-11-11 15:48:24 -08:00 committed by Copybara-Service
parent c7030ac7fa
commit 8ec83d2aa0
1 changed files with 15 additions and 7 deletions
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22
mediapipe/util/android/asset_manager_util.h
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@ -32,17 +32,23 @@ namespace mediapipe {
// Thin wrapper over AAssetManager provided by JNI. This class is meant to be
// used as a singleton.
// Usage: Call InitializeFromActivity from a JNI function that has access to the
// Java activity in the Android application. This initializes the asset manager
// and now files bundled in the assets folder can be read using ReadFile().
//
// Usage: Call one of Initialize* functions from a JNI function that has access
// to a context/activity/etc. This initializes the asset manager and now files
// bundled in the assets folder can be read using ReadFile().
//
// NOTE: initialization should happen strictly once and guaranteed to complete
// before any possible use, otherwise it cannot be used safely across multiple
// threads.
class AssetManager {
public:
AssetManager(const AssetManager&) = delete;
AssetManager& operator=(const AssetManager&) = delete;
// Returns the asset manager if it has been set by a call to
// InitializeFromActivity, otherwise returns nullptr.
// Returns the asset manager if it has been set by one of Initialize*
// functions, otherwise returns nullptr.
AAssetManager* GetAssetManager();
// Returns true if AAssetManager was successfully initialized.
bool InitializeFromAssetManager(JNIEnv* env, jobject local_asset_manager,
const std::string& cache_dir_path);
@ -55,7 +61,7 @@ class AssetManager {
const std::string& cache_dir_path);
// Returns true if AAssetManager was successfully initialized.
ABSL_DEPRECATED("Use InitializeFromActivity instead.")
ABSL_DEPRECATED("Use one of alternate Initialize* functions instead.")
bool InitializeFromAssetManager(JNIEnv* env, jobject local_asset_manager);
// Returns true if AAssetManager was successfully initialized.
@ -79,12 +85,14 @@ class AssetManager {
std::string* output);
// Returns the path to the Android cache directory. Will be empty if
// InitializeFromActivity has not been called.
// AssetManager hasn't been initialized.
const std::string& GetCacheDirPath();
// Caches the contents of the given asset as a file, and returns a path to
// that file. This can be used to pass an asset to APIs that require a path
// to a filesystem file.
// NOTE: this is _not_ thread-safe, e.g. if two threads are requesting the
// same file
absl::StatusOr<std::string> CachedFileFromAsset(
const std::string& asset_path);