Fix issue about multi-engine loading assets throws exception after en…

…gines restart (flutter#34473)

ci/licenses_golden/licenses_flutter

@@ -1356,6 +1356,7 @@ FILE: ../../../flutter/shell/platform/android/android_surface_software.cc
 FILE: ../../../flutter/shell/platform/android/android_surface_software.h
 FILE: ../../../flutter/shell/platform/android/apk_asset_provider.cc
 FILE: ../../../flutter/shell/platform/android/apk_asset_provider.h
+FILE: ../../../flutter/shell/platform/android/apk_asset_provider_unittests.cc
 FILE: ../../../flutter/shell/platform/android/context/android_context.cc
 FILE: ../../../flutter/shell/platform/android/context/android_context.h
 FILE: ../../../flutter/shell/platform/android/external_view_embedder/external_view_embedder.cc

shell/platform/android/BUILD.gn

@@ -41,6 +41,7 @@ executable("flutter_shell_native_unittests") {
   sources = [
     "android_context_gl_unittests.cc",
     "android_shell_holder_unittests.cc",
+    "apk_asset_provider_unittests.cc",
     "flutter_shell_native_unittests.cc",
   ]
   public_configs = [ "//flutter:config" ]

shell/platform/android/android_shell_holder.cc

@@ -259,8 +259,7 @@ std::unique_ptr<AndroidShellHolder> AndroidShellHolder::Spawn(
 
   // TODO(xster): could be worth tracing this to investigate whether
   // the IsolateConfiguration could be cached somewhere.
-  auto config = BuildRunConfiguration(asset_manager_, entrypoint, libraryUrl,
-                                      entrypoint_args);
+  auto config = BuildRunConfiguration(entrypoint, libraryUrl, entrypoint_args);
   if (!config) {
     // If the RunConfiguration was null, the kernel blob wasn't readable.
     // Fail the whole thing.
@@ -277,17 +276,16 @@ std::unique_ptr<AndroidShellHolder> AndroidShellHolder::Spawn(
 }
 
 void AndroidShellHolder::Launch(
-    std::shared_ptr<AssetManager> asset_manager,
+    std::unique_ptr<APKAssetProvider> apk_asset_provider,
     const std::string& entrypoint,
     const std::string& libraryUrl,
     const std::vector<std::string>& entrypoint_args) {
   if (!IsValid()) {
     return;
   }
 
-  asset_manager_ = asset_manager;
-  auto config = BuildRunConfiguration(asset_manager, entrypoint, libraryUrl,
-                                      entrypoint_args);
+  apk_asset_provider_ = std::move(apk_asset_provider);
+  auto config = BuildRunConfiguration(entrypoint, libraryUrl, entrypoint_args);
   if (!config) {
     return;
   }
@@ -314,7 +312,6 @@ void AndroidShellHolder::NotifyLowMemoryWarning() {
 }
 
 std::optional<RunConfiguration> AndroidShellHolder::BuildRunConfiguration(
-    std::shared_ptr<flutter::AssetManager> asset_manager,
     const std::string& entrypoint,
     const std::string& libraryUrl,
     const std::vector<std::string>& entrypoint_args) const {
@@ -333,8 +330,8 @@ std::optional<RunConfiguration> AndroidShellHolder::BuildRunConfiguration(
         IsolateConfiguration::CreateForKernel(std::move(kernel_blob));
   }
 
-  RunConfiguration config(std::move(isolate_configuration),
-                          std::move(asset_manager));
+  RunConfiguration config(std::move(isolate_configuration));
+  config.AddAssetResolver(apk_asset_provider_->Clone());
 
   {
     if (!entrypoint.empty() && !libraryUrl.empty()) {

shell/platform/android/android_shell_holder.h

@@ -15,6 +15,7 @@
 #include "flutter/shell/common/run_configuration.h"
 #include "flutter/shell/common/shell.h"
 #include "flutter/shell/common/thread_host.h"
+#include "flutter/shell/platform/android/apk_asset_provider.h"
 #include "flutter/shell/platform/android/jni/platform_view_android_jni.h"
 #include "flutter/shell/platform/android/platform_message_handler_android.h"
 #include "flutter/shell/platform/android/platform_view_android.h"
@@ -83,7 +84,7 @@ class AndroidShellHolder {
       const std::string& initial_route,
       const std::vector<std::string>& entrypoint_args) const;
 
-  void Launch(std::shared_ptr<AssetManager> asset_manager,
+  void Launch(std::unique_ptr<APKAssetProvider> apk_asset_provider,
               const std::string& entrypoint,
               const std::string& libraryUrl,
               const std::vector<std::string>& entrypoint_args);
@@ -95,8 +96,6 @@ class AndroidShellHolder {
   Rasterizer::Screenshot Screenshot(Rasterizer::ScreenshotType type,
                                     bool base64_encode);
 
-  void UpdateAssetManager(fml::RefPtr<flutter::AssetManager> asset_manager);
-
   void NotifyLowMemoryWarning();
 
   const std::shared_ptr<PlatformMessageHandler>& GetPlatformMessageHandler()
@@ -112,7 +111,7 @@ class AndroidShellHolder {
   std::unique_ptr<Shell> shell_;
   bool is_valid_ = false;
   uint64_t next_pointer_flow_id_ = 0;
-  std::shared_ptr<AssetManager> asset_manager_;
+  std::unique_ptr<APKAssetProvider> apk_asset_provider_;
 
   //----------------------------------------------------------------------------
   /// @brief      Constructor with its components injected.
@@ -132,7 +131,6 @@ class AndroidShellHolder {
                      const fml::WeakPtr<PlatformViewAndroid>& platform_view);
   static void ThreadDestructCallback(void* value);
   std::optional<RunConfiguration> BuildRunConfiguration(
-      std::shared_ptr<flutter::AssetManager> asset_manager,
       const std::string& entrypoint,
       const std::string& libraryUrl,
       const std::vector<std::string>& entrypoint_args) const;

shell/platform/android/apk_asset_provider.cc

@@ -13,29 +13,6 @@
 
 namespace flutter {
 
-APKAssetProvider::APKAssetProvider(JNIEnv* env,
-                                   jobject jassetManager,
-                                   std::string directory)
-    : java_asset_manager_(env, jassetManager),
-      directory_(std::move(directory)) {
-  assetManager_ = AAssetManager_fromJava(env, jassetManager);
-}
-
-APKAssetProvider::~APKAssetProvider() = default;
-
-bool APKAssetProvider::IsValid() const {
-  return true;
-}
-
-bool APKAssetProvider::IsValidAfterAssetManagerChange() const {
-  return true;
-}
-
-// |AssetResolver|
-AssetResolver::AssetResolverType APKAssetProvider::GetType() const {
-  return AssetResolver::AssetResolverType::kApkAssetProvider;
-}
-
 class APKAssetMapping : public fml::Mapping {
  public:
   explicit APKAssetMapping(AAsset* asset) : asset_(asset) {}
@@ -56,17 +33,73 @@ class APKAssetMapping : public fml::Mapping {
   FML_DISALLOW_COPY_AND_ASSIGN(APKAssetMapping);
 };
 
+class APKAssetProviderImpl : public APKAssetProviderInternal {
+ public:
+  explicit APKAssetProviderImpl(JNIEnv* env,
+                                jobject jassetManager,
+                                std::string directory)
+      : java_asset_manager_(env, jassetManager),
+        directory_(std::move(directory)) {
+    asset_manager_ = AAssetManager_fromJava(env, jassetManager);
+  }
+
+  ~APKAssetProviderImpl() = default;
+
+  std::unique_ptr<fml::Mapping> GetAsMapping(
+      const std::string& asset_name) const override {
+    std::stringstream ss;
+    ss << directory_.c_str() << "/" << asset_name;
+    AAsset* asset = AAssetManager_open(asset_manager_, ss.str().c_str(),
+                                       AASSET_MODE_BUFFER);
+    if (!asset) {
+      return nullptr;
+    }
+
+    return std::make_unique<APKAssetMapping>(asset);
+  };
+
+ private:
+  fml::jni::ScopedJavaGlobalRef<jobject> java_asset_manager_;
+  AAssetManager* asset_manager_;
+  const std::string directory_;
+
+  FML_DISALLOW_COPY_AND_ASSIGN(APKAssetProviderImpl);
+};
+
+APKAssetProvider::APKAssetProvider(JNIEnv* env,
+                                   jobject assetManager,
+                                   std::string directory)
+    : impl_(std::make_shared<APKAssetProviderImpl>(env,
+                                                   assetManager,
+                                                   std::move(directory))) {}
+
+APKAssetProvider::APKAssetProvider(
+    std::shared_ptr<APKAssetProviderInternal> impl)
+    : impl_(impl) {}
+
+// |AssetResolver|
+bool APKAssetProvider::IsValid() const {
+  return true;
+}
+
+// |AssetResolver|
+bool APKAssetProvider::IsValidAfterAssetManagerChange() const {
+  return true;
+}
+
+// |AssetResolver|
+AssetResolver::AssetResolverType APKAssetProvider::GetType() const {
+  return AssetResolver::AssetResolverType::kApkAssetProvider;
+}
+
+// |AssetResolver|
 std::unique_ptr<fml::Mapping> APKAssetProvider::GetAsMapping(
     const std::string& asset_name) const {
-  std::stringstream ss;
-  ss << directory_.c_str() << "/" << asset_name;
-  AAsset* asset =
-      AAssetManager_open(assetManager_, ss.str().c_str(), AASSET_MODE_BUFFER);
-  if (!asset) {
-    return nullptr;
-  }
+  return impl_->GetAsMapping(asset_name);
+}
 
-  return std::make_unique<APKAssetMapping>(asset);
+std::unique_ptr<APKAssetProvider> APKAssetProvider::Clone() const {
+  return std::make_unique<APKAssetProvider>(impl_);
 }
 
 }  // namespace flutter

shell/platform/android/apk_asset_provider.h

@@ -14,17 +14,37 @@
 
 namespace flutter {
 
+class APKAssetProviderInternal {
+ public:
+  virtual std::unique_ptr<fml::Mapping> GetAsMapping(
+      const std::string& asset_name) const = 0;
+
+ protected:
+  virtual ~APKAssetProviderInternal() = default;
+};
+
 class APKAssetProvider final : public AssetResolver {
  public:
   explicit APKAssetProvider(JNIEnv* env,
                             jobject assetManager,
                             std::string directory);
-  ~APKAssetProvider() override;
+
+  explicit APKAssetProvider(std::shared_ptr<APKAssetProviderInternal> impl);
+
+  ~APKAssetProvider() = default;
+
+  // Returns a new 'std::unique_ptr<APKAssetProvider>' with the same 'impl_' as
+  // this provider.
+  std::unique_ptr<APKAssetProvider> Clone() const;
+
+  // Obtain a raw pointer to the APKAssetProviderInternal.
+  //
+  // This method is intended for use in tests. Callers must not
+  // delete the returned pointer.
+  APKAssetProviderInternal* GetImpl() const { return impl_.get(); }
 
  private:
-  fml::jni::ScopedJavaGlobalRef<jobject> java_asset_manager_;
-  AAssetManager* assetManager_;
-  const std::string directory_;
+  std::shared_ptr<APKAssetProviderInternal> impl_;
 
   // |flutter::AssetResolver|
   bool IsValid() const override;

shell/platform/android/apk_asset_provider_unittests.cc

@@ -0,0 +1,25 @@
+#include "flutter/shell/platform/android/apk_asset_provider.h"
+#include "gmock/gmock.h"
+#include "gtest/gtest.h"
+
+namespace flutter {
+namespace testing {
+class MockAPKAssetProviderImpl : public APKAssetProviderInternal {
+ public:
+  MOCK_CONST_METHOD1(
+      GetAsMapping,
+      std::unique_ptr<fml::Mapping>(const std::string& asset_name));
+};
+
+TEST(APKAssetProvider, Clone) {
+  auto first_provider = std::make_unique<APKAssetProvider>(
+      std::make_shared<MockAPKAssetProviderImpl>());
+  auto second_provider = std::make_unique<APKAssetProvider>(
+      std::make_shared<MockAPKAssetProviderImpl>());
+  auto third_provider = first_provider->Clone();
+
+  ASSERT_NE(first_provider->GetImpl(), second_provider->GetImpl());
+  ASSERT_EQ(first_provider->GetImpl(), third_provider->GetImpl());
+}
+}  // namespace testing
+}  // namespace flutter

shell/platform/android/platform_view_android_jni_impl.cc

@@ -241,20 +241,17 @@ static void RunBundleAndSnapshotFromLibrary(JNIEnv* env,
                                             jstring jLibraryUrl,
                                             jobject jAssetManager,
                                             jobject jEntrypointArgs) {
-  auto asset_manager = std::make_shared<flutter::AssetManager>();
-
-  asset_manager->PushBack(std::make_unique<flutter::APKAssetProvider>(
-      env,                                             // jni environment
-      jAssetManager,                                   // asset manager
-      fml::jni::JavaStringToString(env, jBundlePath))  // apk asset dir
+  auto apk_asset_provider = std::make_unique<flutter::APKAssetProvider>(
+      env,                                            // jni environment
+      jAssetManager,                                  // asset manager
+      fml::jni::JavaStringToString(env, jBundlePath)  // apk asset dir
   );
-
   auto entrypoint = fml::jni::JavaStringToString(env, jEntrypoint);
   auto libraryUrl = fml::jni::JavaStringToString(env, jLibraryUrl);
   auto entrypoint_args = fml::jni::StringListToVector(env, jEntrypointArgs);
 
-  ANDROID_SHELL_HOLDER->Launch(asset_manager, entrypoint, libraryUrl,
-                               entrypoint_args);
+  ANDROID_SHELL_HOLDER->Launch(std::move(apk_asset_provider), entrypoint,
+                               libraryUrl, entrypoint_args);
 }
 
 static jobject LookupCallbackInformation(JNIEnv* env,