[camera] Improve the camera example with controllers initializations

packages/camera/camera/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.9.6+1
+
+* Improve the example to update the controller only if it's initialized successfully.
+
 ## 0.9.6
 
 * Adds audio access permission handling logic on iOS to fix an issue with `prepareForVideoRecording` not awaiting for the audio permission request result.

packages/camera/camera/example/lib/main.dart

@@ -651,39 +651,45 @@ class _CameraExampleHomeState extends State<CameraExampleHome>
       imageFormatGroup: ImageFormatGroup.jpeg,
     );
 
-    controller = cameraController;
-
     // If the controller is updated then update the UI.
     cameraController.addListener(() {
       if (mounted) {
         setState(() {});
       }
       if (cameraController.value.hasError) {
         showInSnackBar(
-            'Camera error ${cameraController.value.errorDescription}');
+          'Camera error ${cameraController.value.errorDescription}',
+        );
       }
     });
 
     try {
       await cameraController.initialize();
       await Future.wait(<Future<Object?>>[
         // The exposure mode is currently not supported on the web.
-        ...!kIsWeb
-            ? <Future<Object?>>[
-                cameraController.getMinExposureOffset().then(
-                    (double value) => _minAvailableExposureOffset = value),
-                cameraController
-                    .getMaxExposureOffset()
-                    .then((double value) => _maxAvailableExposureOffset = value)
-              ]
-            : <Future<Object?>>[],
+        if (!kIsWeb) ...<Future<Object?>>[
+          cameraController
+              .getMinExposureOffset()
+              .then((double value) => _minAvailableExposureOffset = value),
+          cameraController
+              .getMaxExposureOffset()
+              .then((double value) => _maxAvailableExposureOffset = value),
+        ],
         cameraController
             .getMaxZoomLevel()
             .then((double value) => _maxAvailableZoom = value),
         cameraController
             .getMinZoomLevel()
             .then((double value) => _minAvailableZoom = value),
       ]);
+      // `controller` needs to be set until it's fully initialized to avoid a
+      // race condition when the lifecycle callback is being called and creates
+      // a new `controller`. This happens when the camera permission dialog
+      // dismisses at the first run, which triggers `didChangeAppLifecycleState`
+      // that disposes and re-creates the controller. Switching controllers in a
+      // short circumstance might cause the camera preview flashes or make the
+      // state hard to manage.
+      controller = cameraController;
     } on CameraException catch (e) {
       switch (e.code) {
         case 'CameraAccessDenied':

packages/camera/camera/pubspec.yaml

@@ -4,7 +4,7 @@ description: A Flutter plugin for controlling the camera. Supports previewing
   Dart.
 repository: https://github.com/flutter/plugins/tree/main/packages/camera/camera
 issue_tracker: https://github.com/flutter/flutter/issues?q=is%3Aissue+is%3Aopen+label%3A%22p%3A+camera%22
-version: 0.9.6
+version: 0.9.6+1
 
 environment:
   sdk: ">=2.14.0 <3.0.0"