Convert ReactApplication to kotlin (#37987)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/37987

Convert ReactApplication to kotlin

bypass-github-export-checks

changelog: [internal] internal

Reviewed By: cortinico

Differential Revision: D46772472

fbshipit-source-id: 70c6b9fad3e4e365434b59f184753ca23cf5ed56

packages/react-native/ReactAndroid/build.gradle

@@ -471,6 +471,11 @@ android {
         targetCompatibility = JavaVersion.VERSION_11
     }
 
+    kotlinOptions {
+        // Using '-Xjvm-default=all' to support usage of @JvmDefault in kotlin files
+        freeCompilerArgs = ['-Xjvm-default=all']
+    }
+
     defaultConfig {
         minSdk = 21
         targetSdk = 33

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactActivityDelegate.java

@@ -89,7 +89,7 @@ public class ReactActivityDelegate {
   }
 
   public ReactHostInterface getReactHost() {
-    return ((ReactApplication) getPlainActivity().getApplication()).getReactHostInterface();
+    return ((ReactApplication) getPlainActivity().getApplication()).reactHostInterface();
   }
 
   public ReactInstanceManager getReactInstanceManager() {

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactApplication.java

@@ -1,26 +0,0 @@
-/*
- * Copyright (c) Meta Platforms, Inc. and affiliates.
- *
- * This source code is licensed under the MIT license found in the
- * LICENSE file in the root directory of this source tree.
- */
-
-package com.facebook.react;
-
-import androidx.annotation.Nullable;
-import com.facebook.react.interfaces.ReactHostInterface;
-
-/** Interface that represents an instance of a React Native application */
-public interface ReactApplication {
-
-  /** Get the default {@link ReactNativeHost} for this app. */
-  ReactNativeHost getReactNativeHost();
-
-  /**
-   * Get the default {@link ReactHostInterface} for this app. This method will be used by the new
-   * architecture of react native
-   */
-  default @Nullable ReactHostInterface getReactHostInterface() {
-    return null;
-  }
-}

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/ReactApplication.kt

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+package com.facebook.react
+
+import com.facebook.react.common.annotations.UnstableReactNativeAPI
+import com.facebook.react.interfaces.ReactHostInterface
+
+@OptIn(UnstableReactNativeAPI::class)
+/** Interface that represents an instance of a React Native application */
+interface ReactApplication {
+  /** Get the default [ReactNativeHost] for this app. */
+  fun getReactNativeHost(): ReactNativeHost
+
+  /**
+   * Get the default [ReactHostInterface] for this app. This method will be used by the new
+   * architecture of react native
+   */
+  @JvmDefault fun reactHostInterface(): ReactHostInterface? = null
+}