Add surfaceId helper to Event baseclass

Summary:
Colocate the surface ID generate with the code that consumes it. This allows us to re-use this method in other event emitter locations.

Changelog: [Android][Changed] Add helper to get surfaceId for event dispatching

Reviewed By: philIip

Differential Revision: D31651881

fbshipit-source-id: 109e189f90261d3ba0077ffa519c3d12a9111439

ReactAndroid/src/main/java/com/facebook/react/uimanager/JSTouchDispatcher.java

@@ -12,7 +12,7 @@ import android.view.ViewGroup;
 import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
 import com.facebook.react.common.ReactConstants;
-import com.facebook.react.uimanager.common.UIManagerType;
+import com.facebook.react.uimanager.events.Event;
 import com.facebook.react.uimanager.events.EventDispatcher;
 import com.facebook.react.uimanager.events.TouchEvent;
 import com.facebook.react.uimanager.events.TouchEventCoalescingKeyHelper;
@@ -51,25 +51,6 @@ public class JSTouchDispatcher {
     mTargetTag = -1;
   }
 
-  /**
-   * See Event.java. By contract, this surfaceId should be a valid SurfaceId in Fabric, and should
-   * ALWAYS return -1 in non-Fabric.
-   *
-   * @return
-   */
-  private int getSurfaceId() {
-    if (mRootViewGroup != null
-        && mRootViewGroup instanceof ReactRoot
-        && ((ReactRoot) mRootViewGroup).getUIManagerType() == UIManagerType.FABRIC) {
-      if (mRootViewGroup.getContext() instanceof ThemedReactContext) {
-        ThemedReactContext context = (ThemedReactContext) mRootViewGroup.getContext();
-        return context.getSurfaceId();
-      }
-      return ((ReactRoot) mRootViewGroup).getRootViewTag();
-    }
-    return -1;
-  }
-
   /**
    * Main catalyst view is responsible for collecting and sending touch events to JS. This method
    * reacts for an incoming android native touch events ({@link MotionEvent}) and calls into {@link
@@ -94,7 +75,7 @@ public class JSTouchDispatcher {
       mTargetTag = findTargetTagAndSetCoordinates(ev);
       eventDispatcher.dispatchEvent(
           TouchEvent.obtain(
-              getSurfaceId(),
+              Event.getSurfaceIdForView(mRootViewGroup),
               mTargetTag,
               TouchEventType.START,
               ev,
@@ -119,7 +100,7 @@ public class JSTouchDispatcher {
       findTargetTagAndSetCoordinates(ev);
       eventDispatcher.dispatchEvent(
           TouchEvent.obtain(
-              getSurfaceId(),
+              Event.getSurfaceIdForView(mRootViewGroup),
               mTargetTag,
               TouchEventType.END,
               ev,
@@ -134,7 +115,7 @@ public class JSTouchDispatcher {
       findTargetTagAndSetCoordinates(ev);
       eventDispatcher.dispatchEvent(
           TouchEvent.obtain(
-              getSurfaceId(),
+              Event.getSurfaceIdForView(mRootViewGroup),
               mTargetTag,
               TouchEventType.MOVE,
               ev,
@@ -146,7 +127,7 @@ public class JSTouchDispatcher {
       // New pointer goes down, this can only happen after ACTION_DOWN is sent for the first pointer
       eventDispatcher.dispatchEvent(
           TouchEvent.obtain(
-              getSurfaceId(),
+              Event.getSurfaceIdForView(mRootViewGroup),
               mTargetTag,
               TouchEventType.START,
               ev,
@@ -158,7 +139,7 @@ public class JSTouchDispatcher {
       // Exactly one of the pointers goes up
       eventDispatcher.dispatchEvent(
           TouchEvent.obtain(
-              getSurfaceId(),
+              Event.getSurfaceIdForView(mRootViewGroup),
               mTargetTag,
               TouchEventType.END,
               ev,
@@ -207,7 +188,7 @@ public class JSTouchDispatcher {
     Assertions.assertNotNull(eventDispatcher)
         .dispatchEvent(
             TouchEvent.obtain(
-                getSurfaceId(),
+                Event.getSurfaceIdForView(mRootViewGroup),
                 mTargetTag,
                 TouchEventType.CANCEL,
                 androidEvent,

ReactAndroid/src/main/java/com/facebook/react/uimanager/events/Event.java

@@ -7,10 +7,13 @@
 
 package com.facebook.react.uimanager.events;
 
+import android.view.View;
 import androidx.annotation.Nullable;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.common.SystemClock;
 import com.facebook.react.uimanager.IllegalViewOperationException;
+import com.facebook.react.uimanager.ReactRoot;
+import com.facebook.react.uimanager.ThemedReactContext;
 import com.facebook.react.uimanager.common.UIManagerType;
 
 /**
@@ -40,6 +43,23 @@ public abstract class Event<T extends Event> {
   private long mTimestampMs;
   private int mUniqueID = sUniqueID++;
 
+  /**
+   * This surfaceId should be a valid SurfaceId in Fabric, and should ALWAYS return -1 in
+   * non-Fabric.
+   */
+  public static int getSurfaceIdForView(@Nullable View view) {
+    if (view != null
+        && view instanceof ReactRoot
+        && ((ReactRoot) view).getUIManagerType() == UIManagerType.FABRIC) {
+      if (view.getContext() instanceof ThemedReactContext) {
+        ThemedReactContext context = (ThemedReactContext) view.getContext();
+        return context.getSurfaceId();
+      }
+      return ((ReactRoot) view).getRootViewTag();
+    }
+    return -1;
+  }
+
   protected Event() {}
 
   @Deprecated