Add protected constructor to decouple ReactFragment lifecycle events …

…from ReactHost (#46425)

Summary:
Pull Request resolved: #46425

It's entirely plausible that one would want to run a ReactFragment that does not tear down the ReactHost when it is destroyed. This adds a protected constructor that can be used to disable host lifecycle events in a ReactFragment. When disabled, the `onDestroy` method of the ReactFragment simply stops the surface attached to it using `ReactDelegate.unloadApp`.

## Changelog

[Android][Added] Flag in ReactFragment to allow unmounting a surface without destroying ReactHost.

Reviewed By: philIip

Differential Revision: D62449779

fbshipit-source-id: a443ed004ced45e0adc95bd43b36d1b80f9f392f

packages/react-native/ReactAndroid/api/ReactAndroid.api

@@ -188,6 +188,7 @@ public class com/facebook/react/ReactFragment : androidx/fragment/app/Fragment,
 	protected static final field ARG_LAUNCH_OPTIONS Ljava/lang/String;
 	protected field mReactDelegate Lcom/facebook/react/ReactDelegate;
 	public fun <init> ()V
+	protected fun <init> (Z)V
 	public fun checkPermission (Ljava/lang/String;II)I
 	public fun checkSelfPermission (Ljava/lang/String;)I
 	protected fun getReactDelegate ()Lcom/facebook/react/ReactDelegate;

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

@@ -32,10 +32,20 @@ public class ReactFragment extends Fragment implements PermissionAwareActivity {
 
   protected ReactDelegate mReactDelegate;
 
+  private final boolean mDisableHostLifecycleEvents;
+
   @Nullable private PermissionListener mPermissionListener;
 
   public ReactFragment() {
     // Required empty public constructor
+    this(false);
+  }
+
+  /**
+   * @param disableHostLifecycleEvents Disable forwarding lifecycle events to the {@link ReactHost}.
+   */
+  protected ReactFragment(boolean disableHostLifecycleEvents) {
+    this.mDisableHostLifecycleEvents = disableHostLifecycleEvents;
   }
 
   /**
@@ -99,19 +109,27 @@ public View onCreateView(
   @Override
   public void onResume() {
     super.onResume();
-    mReactDelegate.onHostResume();
+    if (!mDisableHostLifecycleEvents) {
+      mReactDelegate.onHostResume();
+    }
   }
 
   @Override
   public void onPause() {
     super.onPause();
-    mReactDelegate.onHostPause();
+    if (!mDisableHostLifecycleEvents) {
+      mReactDelegate.onHostPause();
+    }
   }
 
   @Override
   public void onDestroy() {
     super.onDestroy();
-    mReactDelegate.onHostDestroy();
+    if (!mDisableHostLifecycleEvents) {
+      mReactDelegate.onHostDestroy();
+    } else {
+      mReactDelegate.unloadApp();
+    }
   }
 
   // endregion