fix(sample): gate deferred-init to Android and make startMParticle idempotent

Addresses review feedback:
- index.js: only run the first-frame DeferredInit call on Android, so iOS no
  longer logs a spurious 'module not available' warning every launch.
- DeferredInitModule: short-circuit startMParticle() when MParticle is already
  started, so repeat JS calls (Fast Refresh / remounts) don't double-register
  lifecycle callbacks or re-start the SDK.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: nickolas-dimitrakas

sample/android/app/src/main/java/com/mparticlesample/DeferredInitModule.kt

@@ -68,6 +68,13 @@ class DeferredInitModule(private val reactContext: ReactApplicationContext) :
             return
         }
 
+        // Idempotent: JS may invoke this more than once (Fast Refresh, remounts). Once mParticle
+        // has started, skip re-registering the lifecycle observer and re-starting the SDK.
+        if (MParticle.getInstance() != null) {
+            promise.resolve("already started")
+            return
+        }
+
         Log.i(TAG, "startMParticle() called from JS (post first-frame). MParticle.getInstance()=${MParticle.getInstance()}")
 
         val app = reactContext.applicationContext as Application

sample/index.js

@@ -171,22 +171,26 @@ export default class MParticleSample extends Component {
   }
 
   componentDidMount() {
-    // Deferred-init edge-case example (Android). When DeferredInitModule.DEFERRED_INIT_EXAMPLE
-    // is enabled, mParticle is started from the native module at the moment the first frame is
-    // painted, instead of in MainApplication.onCreate(). requestAnimationFrame fires after the
-    // first frame is committed -- by which point MainActivity has already RESUMED, which is what
-    // triggers the Rokt overlay Activity-capture race. When the flag is off (default) this is a
-    // no-op. See DeferredInitModule.kt for the full explanation.
-    requestAnimationFrame(() => {
-      const {DeferredInit} = NativeModules;
-      if (DeferredInit) {
-        DeferredInit.startMParticle()
-          .then(r => console.log('Deferred MParticle.start ->', r))
-          .catch(e => console.warn('Deferred start failed', e));
-      } else {
-        console.warn('DeferredInit native module not available');
-      }
-    });
+    // Deferred-init edge-case example (Android only). The DeferredInit native module exists only
+    // on Android; iOS resolves the presenter lazily and is unaffected, so we skip it there to keep
+    // iOS quiet. When DeferredInitModule.DEFERRED_INIT_EXAMPLE is enabled, mParticle is started
+    // from the native module at the moment the first frame is painted, instead of in
+    // MainApplication.onCreate(). requestAnimationFrame fires after the first frame is committed --
+    // by which point MainActivity has already RESUMED, which is what triggers the Rokt overlay
+    // Activity-capture race. When the flag is off (default) this is a no-op on the native side.
+    // See DeferredInitModule.kt for the full explanation.
+    if (Platform.OS === 'android') {
+      requestAnimationFrame(() => {
+        const {DeferredInit} = NativeModules;
+        if (DeferredInit) {
+          DeferredInit.startMParticle()
+            .then(r => console.log('Deferred MParticle.start ->', r))
+            .catch(e => console.warn('Deferred start failed', e));
+        } else {
+          console.warn('DeferredInit native module not available');
+        }
+      });
+    }
 
     MParticle.getSession(session => this.setState({session}));