Support hot and cold reload when using the APK asset provider on Android (#4746)

* deprecate snapshot_override, which is an obsolete predecessor of hot reload
* give the APKAssetProvider to the engine in the initial call to RunBundle
* later calls to Engine::RunBundleAndSource or Engine::SetAssetBundlePath
  will replace the APK asset provider with a DirectoryAssetBundle that uses
  the newly pushed assets

shell/common/engine.cc

@@ -301,7 +301,14 @@ void Engine::RunBundle(const std::string& bundle_path,
                        bool reuse_runtime_controller) {
   TRACE_EVENT0("flutter", "Engine::RunBundle");
   ConfigureAssetBundle(bundle_path);
-  ConfigureRuntime(GetScriptUriFromPath(bundle_path), reuse_runtime_controller);
+  DoRunBundle(GetScriptUriFromPath(bundle_path), entrypoint,
+              reuse_runtime_controller);
+}
+
+void Engine::DoRunBundle(const std::string& script_uri,
+                         const std::string& entrypoint,
+                         bool reuse_runtime_controller) {
+  ConfigureRuntime(script_uri, reuse_runtime_controller);
   if (blink::IsRunningPrecompiledCode()) {
     runtime_->dart_controller()->RunFromPrecompiledSnapshot(entrypoint);
   } else {
@@ -318,26 +325,16 @@ void Engine::RunBundle(const std::string& bundle_path,
   }
 }
 
-void Engine::RunBundleAndSnapshot(const std::string& bundle_path,
-                                  const std::string& snapshot_override,
-                                  const std::string& entrypoint,
-                                  bool reuse_runtime_controller) {
-  TRACE_EVENT0("flutter", "Engine::RunBundleAndSnapshot");
-  if (snapshot_override.empty()) {
-    RunBundle(bundle_path, entrypoint, reuse_runtime_controller);
-    return;
-  }
-  ConfigureAssetBundle(bundle_path);
-  ConfigureRuntime(GetScriptUriFromPath(bundle_path), reuse_runtime_controller);
-  if (blink::IsRunningPrecompiledCode()) {
-    runtime_->dart_controller()->RunFromPrecompiledSnapshot(entrypoint);
-  } else {
-    std::vector<uint8_t> snapshot;
-    if (!files::ReadFileToVector(snapshot_override, &snapshot))
-      return;
-    runtime_->dart_controller()->RunFromScriptSnapshot(
-        snapshot.data(), snapshot.size(), entrypoint);
-  }
+// TODO(jsimmons): merge this with RunBundle
+void Engine::RunBundleWithAssets(
+    fxl::RefPtr<blink::AssetProvider> asset_provider,
+    const std::string& bundle_path,
+    const std::string& entrypoint,
+    bool reuse_runtime_controller) {
+  TRACE_EVENT0("flutter", "Engine::RunBundleWithAssets");
+  asset_provider_ = asset_provider;
+  DoRunBundle(GetScriptUriFromPath(bundle_path), entrypoint,
+              reuse_runtime_controller);
 }
 
 void Engine::RunBundleAndSource(const std::string& bundle_path,
@@ -572,11 +569,7 @@ void Engine::SetSemanticsEnabled(bool enabled) {
 }
 
 void Engine::ConfigureAssetBundle(const std::string& path) {
-  auto platform_view = platform_view_.lock();
-  asset_provider_ = platform_view->GetAssetProvider();
-  if (!asset_provider_) {
-    asset_provider_ = fxl::MakeRefCounted<blink::DirectoryAssetBundle>(path);
-  }
+  asset_provider_ = fxl::MakeRefCounted<blink::DirectoryAssetBundle>(path);
 
   struct stat stat_result = {};
 

shell/common/engine.h

@@ -40,13 +40,11 @@ class Engine : public blink::RuntimeDelegate {
                  const std::string& entrypoint = main_entrypoint_,
                  bool reuse_runtime_controller = false);
 
-  // Uses the given snapshot instead of looking inside the bundle for the
-  // snapshot. If |snapshot_override| is empty, this function looks for the
-  // snapshot in the bundle itself.
-  void RunBundleAndSnapshot(const std::string& bundle_path,
-                            const std::string& snapshot_override,
-                            const std::string& entrypoint = main_entrypoint_,
-                            bool reuse_runtime_controller = false);
+  // Uses the given provider to locate assets.
+  void RunBundleWithAssets(fxl::RefPtr<blink::AssetProvider> asset_provider,
+                           const std::string& bundle_path,
+                           const std::string& entrypoint = main_entrypoint_,
+                           bool reuse_runtime_controller = false);
 
   // Uses the given source code instead of looking inside the bundle for the
   // source code.
@@ -95,6 +93,10 @@ class Engine : public blink::RuntimeDelegate {
   void StopAnimator();
   void StartAnimatorIfPossible();
 
+  void DoRunBundle(const std::string& script_uri,
+                   const std::string& entrypoint,
+                   bool reuse_runtime_controller);
+
   void ConfigureAssetBundle(const std::string& path);
   void ConfigureRuntime(const std::string& script_uri,
                         bool reuse_runtime_controller = false);

shell/common/platform_view.cc

@@ -126,10 +126,6 @@ VsyncWaiter* PlatformView::GetVsyncWaiter() {
   return vsync_waiter_.get();
 }
 
-fxl::RefPtr<blink::AssetProvider> PlatformView::GetAssetProvider() {
-  return asset_provider_;
-}
-
 void PlatformView::UpdateSemantics(blink::SemanticsNodeUpdates update) {}
 
 void PlatformView::HandlePlatformMessage(

shell/common/platform_view.h

@@ -7,7 +7,6 @@
 
 #include <memory>
 
-#include "flutter/assets/asset_provider.h"
 #include "flutter/flow/texture.h"
 #include "flutter/lib/ui/semantics/semantics_node.h"
 #include "flutter/shell/common/engine.h"
@@ -65,8 +64,6 @@ class PlatformView : public std::enable_shared_from_this<PlatformView> {
   virtual void HandlePlatformMessage(
       fxl::RefPtr<blink::PlatformMessage> message);
 
-  virtual fxl::RefPtr<blink::AssetProvider> GetAssetProvider();
-
   // Called once per texture, on the platform thread.
   void RegisterTexture(std::shared_ptr<flow::Texture> texture);
 
@@ -100,7 +97,6 @@ class PlatformView : public std::enable_shared_from_this<PlatformView> {
   flow::TextureRegistry texture_registry_;
   std::unique_ptr<Engine> engine_;
   std::unique_ptr<VsyncWaiter> vsync_waiter_;
-  fxl::RefPtr<blink::AssetProvider> asset_provider_;
 
   SkISize size_;
 

shell/platform/android/platform_view_android.cc

@@ -213,22 +213,28 @@ void PlatformViewAndroid::RunBundleAndSnapshot(JNIEnv* env, std::string bundle_p
                                                std::string entrypoint,
                                                bool reuse_runtime_controller,
                                                jobject assetManager) {
-  // The flutter assets directory name is the last directory of the bundle_path and the path into the APK
+  // TODO(jsimmons): remove snapshot_override from the public FlutterView API
+  FXL_CHECK(snapshot_override.empty()) << "snapshot_override is obsolete";
+
+  // The flutter assets directory name is the last directory of the bundle_path
+  // and the path into the APK
   size_t last_slash_idx = bundle_path.rfind("/", bundle_path.size());
-  std::string flutter_assets_dir = bundle_path.substr(last_slash_idx+1, bundle_path.size()-last_slash_idx);
+  std::string flutter_assets_dir = bundle_path.substr(
+      last_slash_idx + 1, bundle_path.size() - last_slash_idx);
 
-  asset_provider_ = fxl::MakeRefCounted<blink::APKAssetProvider>(env, assetManager, flutter_assets_dir);
-  blink::Threads::UI()->PostTask([
-    engine = engine_->GetWeakPtr(), bundle_path = std::move(bundle_path),
-    snapshot_override = std::move(snapshot_override),
-    entrypoint = std::move(entrypoint),
-    reuse_runtime_controller = reuse_runtime_controller
-  ] {
-    if (engine)
-      engine->RunBundleAndSnapshot(
-          std::move(bundle_path), std::move(snapshot_override),
-          std::move(entrypoint), reuse_runtime_controller);
-  });
+  fxl::RefPtr<blink::AssetProvider> asset_provider =
+      fxl::MakeRefCounted<blink::APKAssetProvider>(env, assetManager,
+                                                   flutter_assets_dir);
+  blink::Threads::UI()->PostTask(
+      [engine = engine_->GetWeakPtr(),
+       asset_provider = std::move(asset_provider),
+       bundle_path = std::move(bundle_path), entrypoint = std::move(entrypoint),
+       reuse_runtime_controller = reuse_runtime_controller] {
+        if (engine)
+          engine->RunBundleWithAssets(
+              std::move(asset_provider), std::move(bundle_path),
+              std::move(entrypoint), reuse_runtime_controller);
+      });
 }
 
 void PlatformViewAndroid::RunBundleAndSource(std::string bundle_path,