Initializing camera for list of available cameras in Future - flutter

Question

I am using this code that I got directly from pub.dev regarding initializing the camera and creating a list of available cameras
the list is created in a Future main() function but it is not being automatically called when I navigate to the CameraApp page. Has anyone run into this issue? How do I initialize the camera and create the list of available cameras when it navigates to the page with this code? Please help, thank you.
/// CameraApp is the Main Application.
class CameraApp extends StatelessWidget {
/// Default Constructor
const CameraApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return const MaterialApp(
home: CameraExampleHome(),
);
}
}
List<CameraDescription> _cameras = <CameraDescription>[];
Future<void> main() async {
// Fetch the available cameras before initializing the app.
try {
WidgetsFlutterBinding.ensureInitialized();
_cameras = await availableCameras();
} on CameraException catch (e) {
_logError(e.code, e.description);
}
runApp(const CameraApp());
}
And this is the code where I call the CameraApp function from inside a button:
ElevatedButton(
onPressed: ()
{Navigator.push(
context,
MaterialPageRoute(
builder: (context) => CameraApp()));},
child: const Text('Camera'),
style: ElevatedButton.styleFrom(
minimumSize: const Size(160.0, 35.0)),
),

Answer 1

You can create a kind of singleton to manage camera operations.
class CameraManager {
// Declare your camera list here
List<CameraDescription> _cameras = <CameraDescription>[];
// Constructor
CameraManager._privateConstructor() {}
// initialise instance
static final CameraManager instance =
CameraManager._privateConstructor();
// Add a getter to access camera list
List<CameraDescription> get cameras => _cameras;
// Init method
init() async {
try {
_cameras = await availableCameras();
} on CameraException catch (e) {
_logError(e.code, e.description);
}
}
// other needed methods to manage camera
...
}
And then in you main function
Future<void> main() async {
// Fetch the available cameras before initializing the app.
try {
WidgetsFlutterBinding.ensureInitialized();
await CameraManager.instance.init();
}
runApp(const CameraApp());
}
Then on other part of your application, you can import the singleton and access methods and properties with CameraManager.instance.*, for example CameraManager.instance.cameras access _cameras through the getter.

Answer 2

There are few things to consider here.. The implementation you did was right but you named the cameras as a private variable which will be accessed in a single dart file by adding an _ like _cameras. Removing that will make it globally available in all classes just by importing main.dart
Here is the full code
main.dart
import 'package:camera/camera.dart';
import 'package:flutter/material.dart';
import 'package:trial/CameraExampleHome.dart';
List<CameraDescription> cameras = <CameraDescription>[];
void main() async {
try {
WidgetsFlutterBinding.ensureInitialized();
cameras = await availableCameras();
print(cameras);
} on CameraException catch (e) {
print(e.toString());
}
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return MaterialApp(home: CameraApp());
}
}
class CameraApp extends StatelessWidget {
/// Default Constructor
const CameraApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return const MaterialApp(
home: CameraExampleHome(),
);
}
}
cameraExampleHome.dart
import 'package:flutter/material.dart';
import 'main.dart';
class CameraExampleHome extends StatefulWidget {
const CameraExampleHome({Key? key}) : super(key: key);
#override
State<CameraExampleHome> createState() => _CameraExampleHomeState();
}
class _CameraExampleHomeState extends State<CameraExampleHome> {
#override
Widget build(BuildContext context) {
return Scaffold(
body: Center(
child: Text("Available Cameras $cameras"),
//output: Available Cameras [CameraDescription(0, CameraLensDirection.back, 90), CameraDescription(1, CameraLensDirection.front, 270), CameraDescription(2, CameraLensDirection.front, 270)]
),
);
}
}

Answer 3

You could create a library file for Global Variables.
Create a file called "globals.dart" in your lib folder.
Declare the following line at the top.
library your_project_name.globals;
Then set your variable in it
List<CameraDescription> cameras = <CameraDescription>[];
Usage in main
import 'globals.dart' as globals;
main() {
...
globals.cameras = await availableCameras();
...
}
Then simply use the variable anywhere in your project.
import 'globals.dart' as globals;
globals.cameras...

Answer 4

Declare list of CameraDescription global instance as below:
List<CameraDescription> cameras = <CameraDescription>[];
Now you can access the camera instance by importing main.dart , _ always make the instance variable private which will not be accessible outside the file