AssetResolver updating in AssetManager for Dynamic features

assets/asset_manager.cc

@@ -29,6 +29,30 @@ void AssetManager::PushBack(std::unique_ptr<AssetResolver> resolver) {
   resolvers_.push_back(std::move(resolver));
 }
 
+void AssetManager::UpdateResolverByType(
+    std::unique_ptr<AssetResolver> updated_asset_resolver,
+    AssetResolver::AssetResolverType type) {
+  if (updated_asset_resolver == nullptr) {
+    return;
+  }
+  bool updated = false;
+  std::deque<std::unique_ptr<AssetResolver>> new_resolvers;
+  for (auto& old_resolver : resolvers_) {
+    if (!updated && old_resolver->GetType() == type) {
+      // Push the replacement updated resolver in place of the old_resolver.
+      new_resolvers.push_back(std::move(updated_asset_resolver));
+      updated = true;
+    } else {
+      new_resolvers.push_back(std::move(old_resolver));
+    }
+  }
+  // Append resolver to the end if not used as a replacement.
+  if (!updated) {
+    new_resolvers.push_back(std::move(updated_asset_resolver));
+  }
+  resolvers_.swap(new_resolvers);
+}
+
 std::deque<std::unique_ptr<AssetResolver>> AssetManager::TakeResolvers() {
   return std::move(resolvers_);
 }
@@ -79,4 +103,9 @@ bool AssetManager::IsValidAfterAssetManagerChange() const {
   return false;
 }
 
+// |AssetResolver|
+AssetResolver::AssetResolverType AssetManager::GetType() const {
+  return AssetResolverType::kAssetManager;
+}
+
 }  // namespace flutter

assets/asset_manager.h

@@ -25,6 +25,34 @@ class AssetManager final : public AssetResolver {
 
   void PushBack(std::unique_ptr<AssetResolver> resolver);
 
+  //--------------------------------------------------------------------------
+  /// @brief      Replaces an asset resolver of the specified `type` with
+  ///             `updated_asset_resolver`. The matching AssetResolver is
+  ///             removed and replaced with `updated_asset_resolvers`.
+  ///
+  ///             AssetResolvers should be updated when the existing resolver
+  ///             becomes obsolete and a newer one becomes available that
+  ///             provides updated access to the same type of assets as the
+  ///             existing one. This update process is meant to be performed
+  ///             at runtime.
+  ///
+  ///             If a null resolver is provided, nothing will be done. If no
+  ///             matching resolver is found, the provided resolver will be
+  ///             added to the end of the AssetManager resolvers queue. The
+  ///             replacement only occurs with the first matching resolver.
+  ///             Any additional matching resolvers are untouched.
+  ///
+  /// @param[in]  updated_asset_resolver  The asset resolver to replace the
+  ///             resolver of matching type with.
+  ///
+  /// @param[in]  type  The type of AssetResolver to update. Only resolvers of
+  ///                   the specified type will be replaced by the updated
+  ///                   resolver.
+  ///
+  void UpdateResolverByType(
+      std::unique_ptr<AssetResolver> updated_asset_resolver,
+      AssetResolver::AssetResolverType type);
+
   std::deque<std::unique_ptr<AssetResolver>> TakeResolvers();
 
   // |AssetResolver|
@@ -33,6 +61,9 @@ class AssetManager final : public AssetResolver {
   // |AssetResolver|
   bool IsValidAfterAssetManagerChange() const override;
 
+  // |AssetResolver|
+  AssetResolver::AssetResolverType GetType() const override;
+
   // |AssetResolver|
   std::unique_ptr<fml::Mapping> GetAsMapping(
       const std::string& asset_name) const override;

assets/asset_resolver.h

@@ -19,6 +19,15 @@ class AssetResolver {
 
   virtual ~AssetResolver() = default;
 
+  //----------------------------------------------------------------------------
+  /// @brief      Identifies the type of AssetResolver an instance is.
+  ///
+  enum AssetResolverType {
+    kAssetManager,
+    kApkAssetProvider,
+    kDirectoryAssetBundle
+  };
+
   virtual bool IsValid() const = 0;
 
   //----------------------------------------------------------------------------
@@ -39,6 +48,14 @@ class AssetResolver {
   ///
   virtual bool IsValidAfterAssetManagerChange() const = 0;
 
+  //----------------------------------------------------------------------------
+  /// @brief      Gets the type of AssetResolver this is. Types are defined in
+  ///             AssetResolverType.
+  ///
+  /// @return     Returns the AssetResolverType that this resolver is.
+  ///
+  virtual AssetResolverType GetType() const = 0;
+
   [[nodiscard]] virtual std::unique_ptr<fml::Mapping> GetAsMapping(
       const std::string& asset_name) const = 0;
 

assets/directory_asset_bundle.cc

@@ -36,6 +36,11 @@ bool DirectoryAssetBundle::IsValidAfterAssetManagerChange() const {
   return is_valid_after_asset_manager_change_;
 }
 
+// |AssetResolver|
+AssetResolver::AssetResolverType DirectoryAssetBundle::GetType() const {
+  return AssetResolver::AssetResolverType::kDirectoryAssetBundle;
+}
+
 // |AssetResolver|
 std::unique_ptr<fml::Mapping> DirectoryAssetBundle::GetAsMapping(
     const std::string& asset_name) const {

assets/directory_asset_bundle.h

@@ -30,6 +30,9 @@ class DirectoryAssetBundle : public AssetResolver {
   // |AssetResolver|
   bool IsValidAfterAssetManagerChange() const override;
 
+  // |AssetResolver|
+  AssetResolver::AssetResolverType GetType() const override;
+
   // |AssetResolver|
   std::unique_ptr<fml::Mapping> GetAsMapping(
       const std::string& asset_name) const override;

shell/common/platform_view.cc

@@ -170,7 +170,10 @@ void PlatformView::LoadDartDeferredLibraryError(intptr_t loading_unit_id,
                                                 const std::string error_message,
                                                 bool transient) {}
 
-void PlatformView::UpdateAssetManager(
-    std::shared_ptr<AssetManager> asset_manager) {}
+void PlatformView::UpdateAssetResolverByType(
+    std::unique_ptr<AssetResolver> updated_asset_resolver,
+    AssetResolver::AssetResolverType type) {
+  delegate_.UpdateAssetResolverByType(std::move(updated_asset_resolver), type);
+}
 
 }  // namespace flutter

shell/common/platform_view.h

@@ -273,15 +273,34 @@ class PlatformView {
                                               const std::string error_message,
                                               bool transient) = 0;
 
-    // TODO(garyq): Implement a proper asset_resolver replacement instead of
-    // overwriting the entire asset manager.
     //--------------------------------------------------------------------------
-    /// @brief      Sets the asset manager of the engine to asset_manager
-    ///
-    /// @param[in]  asset_manager  The asset manager to use.
-    ///
-    virtual void UpdateAssetManager(
-        std::shared_ptr<AssetManager> asset_manager) = 0;
+    /// @brief      Replaces the asset resolver handled by the engine's
+    ///             AssetManager of the specified `type` with
+    ///             `updated_asset_resolver`. The matching AssetResolver is
+    ///             removed and replaced with `updated_asset_resolvers`.
+    ///
+    ///             AssetResolvers should be updated when the existing resolver
+    ///             becomes obsolete and a newer one becomes available that
+    ///             provides updated access to the same type of assets as the
+    ///             existing one. This update process is meant to be performed
+    ///             at runtime.
+    ///
+    ///             If a null resolver is provided, nothing will be done. If no
+    ///             matching resolver is found, the provided resolver will be
+    ///             added to the end of the AssetManager resolvers queue. The
+    ///             replacement only occurs with the first matching resolver.
+    ///             Any additional matching resolvers are untouched.
+    ///
+    /// @param[in]  updated_asset_resolver  The asset resolver to replace the
+    ///             resolver of matching type with.
+    ///
+    /// @param[in]  type  The type of AssetResolver to update. Only resolvers of
+    ///                   the specified type will be replaced by the updated
+    ///                   resolver.
+    ///
+    virtual void UpdateAssetResolverByType(
+        std::unique_ptr<AssetResolver> updated_asset_resolver,
+        AssetResolver::AssetResolverType type) = 0;
   };
 
   //----------------------------------------------------------------------------
@@ -720,14 +739,34 @@ class PlatformView {
                                             const std::string error_message,
                                             bool transient);
 
-  // TODO(garyq): Implement a proper asset_resolver replacement instead of
-  // overwriting the entire asset manager.
   //--------------------------------------------------------------------------
-  /// @brief      Sets the asset manager of the engine to asset_manager
-  ///
-  /// @param[in]  asset_manager  The asset manager to use.
-  ///
-  virtual void UpdateAssetManager(std::shared_ptr<AssetManager> asset_manager);
+  /// @brief      Replaces the asset resolver handled by the engine's
+  ///             AssetManager of the specified `type` with
+  ///             `updated_asset_resolver`. The matching AssetResolver is
+  ///             removed and replaced with `updated_asset_resolvers`.
+  ///
+  ///             AssetResolvers should be updated when the existing resolver
+  ///             becomes obsolete and a newer one becomes available that
+  ///             provides updated access to the same type of assets as the
+  ///             existing one. This update process is meant to be performed
+  ///             at runtime.
+  ///
+  ///             If a null resolver is provided, nothing will be done. If no
+  ///             matching resolver is found, the provided resolver will be
+  ///             added to the end of the AssetManager resolvers queue. The
+  ///             replacement only occurs with the first matching resolver.
+  ///             Any additional matching resolvers are untouched.
+  ///
+  /// @param[in]  updated_asset_resolver  The asset resolver to replace the
+  ///             resolver of matching type with.
+  ///
+  /// @param[in]  type  The type of AssetResolver to update. Only resolvers of
+  ///                   the specified type will be replaced by the updated
+  ///                   resolver.
+  ///
+  virtual void UpdateAssetResolverByType(
+      std::unique_ptr<AssetResolver> updated_asset_resolver,
+      AssetResolver::AssetResolverType type);
 
  protected:
   PlatformView::Delegate& delegate_;

shell/common/shell.cc

@@ -1223,8 +1223,11 @@ void Shell::LoadDartDeferredLibraryError(intptr_t loading_unit_id,
                                         transient);
 }
 
-void Shell::UpdateAssetManager(std::shared_ptr<AssetManager> asset_manager) {
-  engine_->UpdateAssetManager(std::move(asset_manager));
+void Shell::UpdateAssetResolverByType(
+    std::unique_ptr<AssetResolver> updated_asset_resolver,
+    AssetResolver::AssetResolverType type) {
+  engine_->GetAssetManager()->UpdateResolverByType(
+      std::move(updated_asset_resolver), type);
 }
 
 // |Engine::Delegate|

shell/common/shell.h

@@ -536,7 +536,9 @@ class Shell final : public PlatformView::Delegate,
                                     bool transient) override;
 
   // |PlatformView::Delegate|
-  void UpdateAssetManager(std::shared_ptr<AssetManager> asset_manager) override;
+  void UpdateAssetResolverByType(
+      std::unique_ptr<AssetResolver> updated_asset_resolver,
+      AssetResolver::AssetResolverType type) override;
 
   // |Animator::Delegate|
   void OnAnimatorBeginFrame(fml::TimePoint frame_target_time) override;