Update FocusManager platform check to include iOS (#148612)

Both iOS and Android run into issues when the FocusManager starts responding to app lifecycle changes.

Fortunately, this feature is primarily meant for desktop platforms, so the problem can be resolved with a platform check.

fixes flutter/flutter#148475

Author: nate-thegrate

packages/flutter/lib/src/widgets/focus_manager.dart

@@ -1532,12 +1532,21 @@ class FocusManager with DiagnosticableTreeMixin, ChangeNotifier {
     if (kFlutterMemoryAllocationsEnabled) {
       ChangeNotifier.maybeDispatchObjectCreation(this);
     }
-    if (kIsWeb || defaultTargetPlatform != TargetPlatform.android) {
+    final bool shouldListenToAppLifecycle = switch (defaultTargetPlatform) {
+      TargetPlatform.android || TargetPlatform.iOS => false,
+      TargetPlatform.fuchsia || TargetPlatform.linux => true,
+      TargetPlatform.windows || TargetPlatform.macOS => true,
+    };
+    if (shouldListenToAppLifecycle) {
       // It appears that some Android keyboard implementations can cause
       // app lifecycle state changes: adding this listener would cause the
       // text field to unfocus as the user is trying to type.
       //
-      // Until this is resolved, we won't be adding the listener to Android apps.
+      // Additionally, on iOS, input fields aren't automatically populated
+      // with relevant data when using autofill.
+      //
+      // Until these are resolved, we won't be adding the listener to mobile platforms.
+      // https://github.com/flutter/flutter/issues/148475#issuecomment-2118407411
       // https://github.com/flutter/flutter/pull/142930#issuecomment-1981750069
       _appLifecycleListener = _AppLifecycleListener(_appLifecycleChange);
       WidgetsBinding.instance.addObserver(_appLifecycleListener!);

packages/flutter/test/widgets/focus_manager_test.dart

@@ -354,9 +354,13 @@ void main() {
       logs.clear();
     }, variant: KeySimulatorTransitModeVariant.all());
 
-    testWidgets('FocusManager ignores app lifecycle changes on Android.', (WidgetTester tester) async {
-      final bool shouldRespond = kIsWeb || defaultTargetPlatform != TargetPlatform.android;
-      if (shouldRespond) {
+    testWidgets('FocusManager ignores app lifecycle changes on Android and iOS.', (WidgetTester tester) async {
+      final bool shouldListenToAppLifecycle = switch (defaultTargetPlatform) {
+        TargetPlatform.android || TargetPlatform.iOS => false,
+        TargetPlatform.fuchsia || TargetPlatform.linux => true,
+        TargetPlatform.windows || TargetPlatform.macOS => true,
+      };
+      if (shouldListenToAppLifecycle) {
         return;
       }
 
@@ -387,8 +391,12 @@ void main() {
     });
 
     testWidgets('FocusManager responds to app lifecycle changes.', (WidgetTester tester) async {
-      final bool shouldRespond = kIsWeb || defaultTargetPlatform != TargetPlatform.android;
-      if (!shouldRespond) {
+      final bool shouldListenToAppLifecycle = switch (defaultTargetPlatform) {
+        TargetPlatform.android || TargetPlatform.iOS => false,
+        TargetPlatform.fuchsia || TargetPlatform.linux => true,
+        TargetPlatform.windows || TargetPlatform.macOS => true,
+      };
+      if (!shouldListenToAppLifecycle) {
         return;
       }