fix: Black camera screen (#1732)

* This should fix the black screen with the camera scanner * Mark two methods as private * A few more comments * const constructor for CameraHelper * Update packages/smooth_app/lib/pages/scan/lifecycle_manager.dart Co-authored-by: monsieurtanuki <fabrice_fontaine@hotmail.com> * Update packages/smooth_app/lib/pages/scan/lifecycle_manager.dart Co-authored-by: monsieurtanuki <fabrice_fontaine@hotmail.com> Co-authored-by: monsieurtanuki <fabrice_fontaine@hotmail.com>
openfoodfacts · May 4, 2022 · b55b6aa · b55b6aa
1 parent 21253c1
commit b55b6aa
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Showing 6 changed files with 268 additions and 87 deletions.
diff --git a/packages/smooth_app/lib/helpers/camera_helper.dart b/packages/smooth_app/lib/helpers/camera_helper.dart
@@ -0,0 +1,51 @@
+import 'package:camera/camera.dart';
+
+class CameraHelper {
+  const CameraHelper._();
+
+  static List<CameraDescription>? _cameras;
+
+  /// Mandatory method to call before [findBestCamera]
+  static Future<void> init() async {
+    _cameras = await availableCameras();
+  }
+
+  /// Find the most relevant camera to use if none of these criteria are met,
+  /// the default value of [_cameraIndex] will be used to select the first
+  /// camera in the global cameras list.
+  /// if non matching is found we fall back to the first in the list
+  /// initValue of [_cameraIndex]/
+  static CameraDescription? findBestCamera({
+    CameraLensDirection cameraLensDirection = CameraLensDirection.back,
+  }) {
+    if (_cameras == null) {
+      throw Exception('Please call [init] before!');
+    } else if (_cameras!.isEmpty) {
+      return null;
+    }
+
+    int cameraIndex = -1;
+
+    if (_cameras!.any(
+      (CameraDescription element) =>
+          element.lensDirection == cameraLensDirection &&
+          element.sensorOrientation == 90,
+    )) {
+      cameraIndex = _cameras!.indexOf(
+        _cameras!.firstWhere((CameraDescription element) =>
+            element.lensDirection == cameraLensDirection &&
+            element.sensorOrientation == 90),
+      );
+    } else if (_cameras!.any((CameraDescription element) =>
+        element.lensDirection == cameraLensDirection)) {
+      cameraIndex = _cameras!.indexOf(
+        _cameras!.firstWhere(
+          (CameraDescription element) =>
+              element.lensDirection == cameraLensDirection,
+        ),
+      );
+    }
+
+    return _cameras![cameraIndex];
+  }
+}
diff --git a/packages/smooth_app/lib/main.dart b/packages/smooth_app/lib/main.dart
@@ -1,7 +1,6 @@
 import 'dart:async';
 import 'dart:io' show Platform;
 
-import 'package:camera/camera.dart';
 import 'package:device_preview/device_preview.dart';
 import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
@@ -22,12 +21,11 @@ import 'package:smooth_app/database/dao_string.dart';
 import 'package:smooth_app/database/local_database.dart';
 import 'package:smooth_app/database/product_query.dart';
 import 'package:smooth_app/helpers/analytics_helper.dart';
+import 'package:smooth_app/helpers/camera_helper.dart';
 import 'package:smooth_app/pages/onboarding/onboarding_flow_navigator.dart';
 import 'package:smooth_app/themes/smooth_theme.dart';
 import 'package:smooth_app/themes/theme_provider.dart';
 
-List<CameraDescription> cameras = <CameraDescription>[];
-
 late bool _screenshots;
 
 Future<void> main({final bool screenshots = false}) async {
@@ -103,8 +101,7 @@ Future<bool> _init1() async {
   _themeProvider = ThemeProvider(_userPreferences);
   ProductQuery.setQueryType(_userPreferences);
 
-  cameras = await availableCameras();
-
+  await CameraHelper.init();
   await ProductQuery.setUuid(_localDatabase);
   _init1done = true;
   return true;

diff --git a/packages/smooth_app/lib/pages/scan/lifecycle_manager.dart b/packages/smooth_app/lib/pages/scan/lifecycle_manager.dart
@@ -1,19 +1,27 @@
 import 'package:flutter/cupertino.dart';
 import 'package:flutter/material.dart';
+import 'package:smooth_app/widgets/screen_visibility.dart';
 import 'package:visibility_detector/visibility_detector.dart';
 
-/// This Widgets tracks if the child is currently visible on screen and if the
-/// app gets minimized/resumed by the system
+/// This Widgets tracks both the app lifecycle and the screen visibility
+/// [onStart] will be called only when the Widget is displayed for the first time
+/// (= during the [initState] phase)
+/// [onResume] will be called once the app is reopened (eg: the app is minimized
+/// and brought back to front) or this part of the Widget tree is visible again
+/// [onPause] will be called once the app is minimized or if this part of the
+/// tree is invisible
 class LifeCycleManager extends StatefulWidget {
   const LifeCycleManager({
     required this.onResume,
     required this.onPause,
     required this.child,
+    this.onStart,
     Key? key,
   }) : super(key: key);
 
   final Function() onResume;
   final Function() onPause;
+  final Function()? onStart;
   final Widget child;
 
   @override
@@ -22,29 +30,16 @@ class LifeCycleManager extends StatefulWidget {
 
 class LifeCycleManagerState extends State<LifeCycleManager>
     with WidgetsBindingObserver {
-  double visibleFraction = 100.0;
   AppLifecycleState appLifecycleState = AppLifecycleState.resumed;
 
-  void checkLifeCycle() {
-    if (appLifecycleState == AppLifecycleState.inactive ||
-        visibleFraction == 0.0) {
-      widget.onPause.call();
-    } else if (appLifecycleState == AppLifecycleState.resumed &&
-        visibleFraction > 0.0) {
-      widget.onResume.call();
-    }
-  }
-
   @override
   void initState() {
     super.initState();
     WidgetsBinding.instance!.addObserver(this);
-  }
 
-  @override
-  void dispose() {
-    WidgetsBinding.instance!.removeObserver(this);
-    super.dispose();
+    if (widget.onStart != null) {
+      WidgetsBinding.instance!.addPostFrameCallback((_) => widget.onStart!());
+    }
   }
 
   // Lifecycle changes are not handled by either of the used plugin. This means
@@ -55,18 +50,44 @@ class LifeCycleManagerState extends State<LifeCycleManager>
   @override
   void didChangeAppLifecycleState(AppLifecycleState state) {
     appLifecycleState = state;
-    checkLifeCycle();
+    _onLifeCycleChanged();
+  }
+
+  void _onLifeCycleChanged() {
+    switch (appLifecycleState) {
+      case AppLifecycleState.resumed:
+        widget.onResume();
+        break;
+      case AppLifecycleState.inactive:
+      case AppLifecycleState.paused:
+      case AppLifecycleState.detached:
+        widget.onPause();
+        break;
+    }
+  }
+
+  void _onVisibilityChanged(bool visible) {
+    if (visible) {
+      widget.onResume();
+    } else {
+      widget.onPause();
+    }
   }
 
   @override
   Widget build(BuildContext context) {
     return VisibilityDetector(
       key: const ValueKey<String>('VisibilityDetector'),
       onVisibilityChanged: (VisibilityInfo info) {
-        visibleFraction = info.visibleFraction;
-        checkLifeCycle();
+        _onVisibilityChanged(info.visible);
       },
       child: widget.child,
     );
   }
+
+  @override
+  void dispose() {
+    WidgetsBinding.instance!.removeObserver(this);
+    super.dispose();
+  }
 }