Update the New App template to reduce the amount of C++ code in user …

…space (#34666)

Summary:
Pull Request resolved: #34666

This diff updates the new app template and reduces the amount of C++ code in user space.
From now on users will have to only:
1. Create a CMakeLists.txt file
2. Create an OnLoad.cpp file with the Modules/Components they want to provide.

Changelog:
[Android] [Changed] - Update the template to Reduce the amount of C++ code in user space for New Architecture

Reviewed By: cipolleschi

Differential Revision: D39381762

fbshipit-source-id: 7309b6c61ba9ddd8856cb4aaa6d923ddd816741c

template/android/app/src/main/java/com/helloworld/MainApplication.java

@@ -6,6 +6,7 @@
 import com.facebook.react.ReactNativeHost;
 import com.facebook.react.ReactPackage;
 import com.facebook.react.config.ReactFeatureFlags;
+import com.facebook.react.defaults.DefaultNativeEntryPoint;
 import com.facebook.react.defaults.DefaultReactNativeHost;
 import com.facebook.soloader.SoLoader;
 import java.util.List;
@@ -57,9 +58,9 @@ public void onCreate() {
     SoLoader.init(this, /* native exopackage */ false);
     if (BuildConfig.IS_NEW_ARCHITECTURE_ENABLED) {
       // If you opted-in for the New Architecture, we enable the TurboModule system
-      // and load the native dynamic library for this app.
+      // and load the native entry point for this app.
       ReactFeatureFlags.useTurboModules = true;
-      SoLoader.loadLibrary(BuildConfig.DYNAMIC_LIBRARY_NAME);
+      DefaultNativeEntryPoint.load(BuildConfig.DYNAMIC_LIBRARY_NAME);
     }
     ReactNativeFlipper.initializeFlipper(this, getReactNativeHost().getReactInstanceManager());
   }

template/android/app/src/main/jni/OnLoad.cpp

@@ -1,11 +1,72 @@
+#include <DefaultComponentsRegistry.h>
+#include <DefaultTurboModuleManagerDelegate.h>
 #include <fbjni/fbjni.h>
-#include "MainApplicationTurboModuleManagerDelegate.h"
-#include "MainComponentsRegistry.h"
+#include <react/renderer/componentregistry/ComponentDescriptorProviderRegistry.h>
+#include <rncli.h>
+
+namespace facebook {
+namespace react {
+
+void registerComponents(
+    std::shared_ptr<ComponentDescriptorProviderRegistry const> registry) {
+  // Custom Fabric Components go here. You can register custom
+  // components coming from your App or from 3rd party libraries here.
+  //
+  // providerRegistry->add(concreteComponentDescriptorProvider<
+  //        AocViewerComponentDescriptor>());
+
+  // By default we just use the components autolinked by RN CLI
+  rncli_registerProviders(registry);
+}
+
+std::shared_ptr<TurboModule> provideModules(
+    const std::string &name,
+    const JavaTurboModule::InitParams &params) {
+  // Here you can provide your own module provider for TurboModules coming from
+  // either your application or from external libraries. The approach to follow
+  // is similar to the following (for a library called `samplelibrary`):
+  //
+  // auto module = samplelibrary_ModuleProvider(moduleName, params);
+  // if (module != nullptr) {
+  //    return module;
+  // }
+  // return rncore_ModuleProvider(moduleName, params);
+
+  // By default we just use the module providers autolinked by RN CLI
+  return rncli_ModuleProvider(name, params);
+}
+
+class MainApplicationNativeEntryPoint
+    : public facebook::jni::HybridClass<MainApplicationNativeEntryPoint> {
+ public:
+  constexpr static auto kJavaDescriptor =
+      "Lcom/facebook/react/defaults/DefaultNativeEntryPoint;";
+
+  static jni::local_ref<jhybriddata> initHybrid(jni::alias_ref<jhybridobject>) {
+    DefaultTurboModuleManagerDelegate::moduleProvidersFromEntryPoint =
+        &provideModules;
+    DefaultComponentsRegistry::registerComponentDescriptorsFromEntryPoint =
+        &registerComponents;
+    return makeCxxInstance();
+  }
+
+  static void registerNatives() {
+    registerHybrid({
+        makeNativeMethod(
+            "initHybrid", MainApplicationNativeEntryPoint::initHybrid),
+    });
+  }
+
+ private:
+  friend HybridBase;
+  using HybridBase::HybridBase;
+};
+
+} // namespace react
+} // namespace facebook
 
 JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM *vm, void *) {
   return facebook::jni::initialize(vm, [] {
-    facebook::react::MainApplicationTurboModuleManagerDelegate::
-        registerNatives();
-    facebook::react::MainComponentsRegistry::registerNatives();
+    facebook::react::MainApplicationNativeEntryPoint::registerNatives();
   });
 }