I have a function called control in the StateFull Widget. I want to run this function with WorkManager every 15 minutes.
How can I call the control function from the callbackDispatcher function?
I added a Stream statically to the Statefull widget and then listened to it but it didn't work.
HomeScreen.dart file
import 'package:flutter/material.dart';
import 'package:workmanager/workmanager.dart';
const taskKontrol = "control";
class HomeScreen extends StatefulWidget {
#override
_HomeScreenState createState() => _HomeScreenState();
}
class _HomeScreenState extends State<HomeScreen> {
#override
Widget build(BuildContext context) {
return Container();
}
#override
void initState() {
super.initState();
setupWorkManager();
}
void control() async
{
//... my code control is here
}
}
void setupWorkManager() async {
await Workmanager.initialize(callbackDispatcher, isInDebugMode: true);
Workmanager.registerPeriodicTask(taskKontrol, taskKontrol,
frequency: Duration(seconds: 10),
existingWorkPolicy: ExistingWorkPolicy.append
);
}
void callbackDispatcher() {
Workmanager.executeTask((taskName, inputData) async {
switch(taskName)
{
case taskKontrol:
// How can I call the control function from here?
print("control from workmanager");
break;
}
return Future.value(true);
});
}
For those who still looking for an answer:
From the official docs:
The callbackDispatcher needs to be either a static function or a top level function to be accessible as a Flutter entry point.
I had this same problem and I solved it by moving the function callbackDispatcher to the file: main.dart
Also, the code that initializes callbackDispatcher must be in main() before the App() widget loads.
To call your control code, create a class with static function control()
Note: You cannot call the widget's method from callbackDispatcher!
Reason: Widgets are UI bound. As long as the screen remains active, the widget that is visible remains active. Once you close the app or move on to next screen, the widgets' memory gets recycled. But this callbackDispatcher gets executed even when your app is closed. So, it has to be isolated from UI code.
Here's the code:
main.dart:
import 'package:flutter/material.dart';
import 'package:workmanager/workmanager.dart';
void main() async {
WidgetsFlutterBinding.ensureInitialized();
await Workmanager().initialize(callbackDispatcher, isInDebugMode: true);
runApp(App());
}
void callbackDispatcher() {
Workmanager.executeTask((taskName, inputData) async {
switch(taskName)
{
case ScheduledTask.taskName:
ScheduledTask.control(); // calls your control code
break;
}
return Future.value(true);
});
}
class ScheduledTask {
const static String taskName = "control";
static void control() {
// add your control here
}
}
All you can do from HomeScreen widget is to call setupWorkManager() that schedules the task
class _HomeScreenState extends State<HomeScreen> {
#override
Widget build(BuildContext context) {
return Container();
}
#override
void initState() {
super.initState();
setupWorkManager();
}
}
void setupWorkManager() async {
Workmanager.registerPeriodicTask(taskKontrol, taskKontrol,
frequency: Duration(minutes: 15),
existingWorkPolicy: ExistingWorkPolicy.append
);
}
Note: The minimum frequency for the recurring task is 15 minutes
I am using Flutter with hooks and I am trying to get the App Life Cycle State. I followed documentation and created new hook (code shown below) which works ok for all situations with one exception. When the application state becomes "paused", the hook does not return the value back to the widget. I am not clear what to do at this point. Someone suggested using Isolates but I don't see how that can help. Updating App Life Cycle is not compute expensive.
Please let me know what else I could do make this work.
Thanks
import 'package:flutter/material.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
AppLifecycleState useAppLifecycleState() {
return use(const _LifeCycleState());
}
class _LifeCycleState extends Hook<AppLifecycleState> {
const _LifeCycleState();
#override
__LifeCycleState createState() => __LifeCycleState();
}
class __LifeCycleState extends HookState<AppLifecycleState, _LifeCycleState>
with WidgetsBindingObserver {
AppLifecycleState _state;
#override
void initHook() {
super.initHook();
WidgetsBinding.instance.addObserver(this);
}
#override
void dispose() {
super.dispose();
WidgetsBinding.instance.removeObserver(this);
}
#override
AppLifecycleState build(BuildContext context) {
return _state;
}
#override
void didChangeAppLifecycleState(AppLifecycleState state) {
setState(() {
_state = state;
});
super.didChangeAppLifecycleState(state);
}
}
Thanks for your help.
I kept getting an error from the camera.dart that "name" was being called on a null object.
After some time, I realized that the problem was the that the build method is called before the async code in my initstate finished (I'm actually slightly proud that I understood the problem at least :))
I tried many different ways to initialize my camera properly, but I could not.
This is the last iteration of my code.
What's the idiomatic way of handling this future?
class _PicturePreviewState extends State<PicturePreview> {
List<CameraDescription> cameras;
CameraDescription camera;
CameraController cameraController;
Future<void> initializeController;
Future<void> getCameras() async {
try {
cameras = await availableCameras();
} catch(e) {print(e);}
camera = cameras.last;
print(camera);
}
#override
void initState() {
super.initState();
// getCameras();
availableCameras().then((availableCameras) {
cameras = availableCameras;
camera = cameras.first;
cameraController = CameraController(
camera,
ResolutionPreset.low,
);
initializeController = cameraController.initialize();
print(cameraController.value.isInitialized);
});
// cameraController = CameraController(
// camera,
// ResolutionPreset.low,
// );
// initializeController = cameraController.initialize();
// print(cameraController.value.isInitialized);
}
#override
void dispose() {
cameraController.dispose();
super.dispose();
}
#override
Widget build(BuildContext context) {
return Scaffold(
body: FutureBuilder<void>(
future: initializeController,
builder: (context, snapshot) {
if (snapshot.connectionState == ConnectionState.done) {
// If the Future is complete, display the preview.
return CameraPreview(cameraController);
}
else {
// Otherwise, display a loading indicator.
print(snapshot.connectionState);
return Center(child: CircularProgressIndicator());
}
},
),
I have been relying on this page to use the camera package, but I could not use it verbatim because I can't keep passing down the camera object down my widget tree.
I fixed it.
I put the initializing of the camera object in the in the parent of the widget.
class _TakeReceiptPictureState extends State<TakeReceiptPicture> {
List<CameraDescription> cameras;
CameraDescription camera;
#override
void initState() {
super.initState();
availableCameras().then((availableCameras) {
cameras = availableCameras;
camera = cameras.first;
});
}
Then made the widget that takes the picture have a parameter of type CameraDescription.
class PicturePreview extends StatefulWidget {
final CameraDescription camera;
const PicturePreview(this.camera, {Key key}) : super(key: key);
#override
_PicturePreviewState createState() => _PicturePreviewState();
}
Then passed the camera initialized in the parent to picture widget
onTap: () {
Navigator.of(context).push(
PageTransition(
type: PageTransitionType.transferRight,
child: PicturePreview(camera)),
);
}),
by the time the child widget's build method runs, the camera object is already initialized and ready to go.
Now the state of the child have only two variables, the camera controller and the initialize controller future.
CameraController cameraController;
Future<void> initializeController;
#override
void initState() {
super.initState();
cameraController = CameraController(
widget.camera,
ResolutionPreset.low,
);
initializeController = cameraController.initialize();
}
TLDR: let the initialization of the camera object be the responsibility of the parent of the widget.
Im doing a splashscreen first app, to be followed by a walkthrough page if the user first used the app, else go to a welcome page to sign in/ sign up if already saw the walkthrough screen.
My code came from this projects main.dart file: https://github.com/instaflutter/flutter-login-screen-firebase-auth-facebook-login and modified it to this code(from splashscreen tutorial FlutterKart)
import 'dart:async';
import 'package:flutter/material.dart';
import 'package:cloud_firestore/cloud_firestore.dart';
import 'package:shared_preferences/shared_preferences.dart';
import 'package:binder/ui/screens/root_screen.dart';
import 'package:binder/ui/screens/walk_screen.dart';
void main() {
Firestore.instance.settings(timestampsInSnapshotsEnabled: true);
SharedPreferences.getInstance().then((prefs) {
SplashScreen(prefs: prefs);
});
}
class SplashScreen extends StatefulWidget {
final SharedPreferences prefs;
SplashScreen({Key key,this.prefs}): super(key: key);
#override
_SplashScreenState createState() => _SplashScreenState();
}
class _SplashScreenState extends State<SplashScreen> {
#override
void initState() {
super.initState();
Timer(Duration(seconds: 3), () => _handleCurrentScreen(context));
}
#override
Widget build(BuildContext context) {
final logowhite = Hero(
tag: 'hero',
child: //code insert flutterkart splashscreen
)
],
),
)
],
)
],
),
);
}
Widget _handleCurrentScreen (BuildContext context) {
bool seen = (widget.prefs.getBool('seen') ?? false);
if (seen) {
return new RootScreen();
} else {
return new WalkthroughScreen(prefs: widget.prefs);
}
}
}
I want it to show the splashscreen first and directed to the rootscreen if already seen and to the walkthrough screen if first use.
You'd probably want to use shared_preferences or something similar. Something like this:
// add this static variable somewhere
// could technically be initialized during splash screen and added to a Provider or something similar after
static SharedPreferences prefs;
// make `main` async if it is not already
Future<void> main() async {
prefs = await SharedPreferences.getInstance();
...
}
Future<void> onSplashScreenDone() async {
if (prefs.getBool('isFirstTime') ?? true) {
// you might want to put this at the end of your walkthrough, so they don't miss it if they close the app, for example
await prefs.setBool('isFirstTime', false);
// this is their first time, show walkthrough, etc.
...
} else {
// this is not their first time, do normal things.
}
}
On one of my flutter pages, I need the screen to set to landscape mode and lock it so it can't rotate into portrait mode, but only on the one page. So need a way to enable this function on-the-fly. Anyone know how to do this?
I would like it to rotate landscape-left or landscape-right, just not into portrait mode.
First import the services package:
import 'package:flutter/services.dart';
This will give you access to the SystemChrome class, which "Controls specific aspects of the operating system's graphical interface and how it interacts with the application."
When you load the Widget, do something like this:
#override
void initState(){
super.initState();
SystemChrome.setPreferredOrientations([
DeviceOrientation.landscapeRight,
DeviceOrientation.landscapeLeft,
]);
}
then when I leave the page, put it back to normal like this:
#override
dispose(){
SystemChrome.setPreferredOrientations([
DeviceOrientation.landscapeRight,
DeviceOrientation.landscapeLeft,
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
]);
super.dispose();
}
I would use a simple mixin to lock phone in portrait. The following solution locks the entire app in portrait or sets specific screens to portrait while keeping rotation elsewere.
import 'package:flutter/cupertino.dart';
import 'package:flutter/services.dart';
/// Forces portrait-only mode application-wide
/// Use this Mixin on the main app widget i.e. app.dart
/// Flutter's 'App' has to extend Stateless widget.
///
/// Call `super.build(context)` in the main build() method
/// to enable portrait only mode
mixin PortraitModeMixin on StatelessWidget {
#override
Widget build(BuildContext context) {
_portraitModeOnly();
return null;
}
}
/// Forces portrait-only mode on a specific screen
/// Use this Mixin in the specific screen you want to
/// block to portrait only mode.
///
/// Call `super.build(context)` in the State's build() method
/// and `super.dispose();` in the State's dispose() method
mixin PortraitStatefulModeMixin<T extends StatefulWidget> on State<T> {
#override
Widget build(BuildContext context) {
_portraitModeOnly();
return null;
}
#override
void dispose() {
_enableRotation();
super.dispose();
}
}
/// blocks rotation; sets orientation to: portrait
void _portraitModeOnly() {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
]);
}
void _enableRotation() {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
DeviceOrientation.landscapeLeft,
DeviceOrientation.landscapeRight,
]);
}
To block rotation in the entire app implement PortraitModeMixin in the main App widget. Remember to call super.build(context) in Widget build(BuildContext context) method.
/// Main App widget
class App extends StatelessWidget with PortraitModeMixin {
const App();
#override
Widget build(BuildContext context) {
super.build(context);
return CupertinoApp(
title: 'Flutter Demo',
theme: CupertinoThemeData(),
home: Text("Block screen rotation example"),
);
}
}
To block rotation in a specific screen implement PortraitStatefulModeMixin<SampleScreen> in the specific screen's state. Remember to call super.build(context) in the State's build() method and super.dispose() in dispose() method. If your screen is a StatelessWidget - simply repeat the App's solution (previous example) i.e. use PortraitModeMixin.
/// Specific screen
class SampleScreen extends StatefulWidget {
SampleScreen() : super();
#override
State<StatefulWidget> createState() => _SampleScreenState();
}
class _SampleScreenState extends State<SampleScreen>
with PortraitStatefulModeMixin<SampleScreen> {
#override
Widget build(BuildContext context) {
super.build(context);
return Text("Flutter - Block screen rotation example");
}
#override
void dispose() {
super.dispose();
}
}
Mixins with such syntax work from Dart 2.1
First, Lock the entire app orientation to Portrait mode.
//Do this in main.dart
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((_) {
runApp(MyApp());
});
Second, Go the specific screen where you want to change the orientation.
#override
void initState() {
super.initState();
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.landscapeRight,
DeviceOrientation.landscapeLeft
]);
}
#override
void dispose() {
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
super.dispose();
}
For using SystemChrome you will have to add 'package:flutter/services.dart'
void main() {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp, DeviceOrientation.portraitDown])
.then((_) {
runApp(new MyApp());
});
}
import services.dart package and add following code to lock device orientation to portraitUp mode:
import 'package:flutter/services.dart';
main() {
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
runApp(MyHomePage());
}
Sometimes it could not work due to null info about orientation.
You can use it simply like this:
import services.dart
void main() {
SystemChrome.setPreferredOrientations(
[DeviceOrientation.portraitUp]
)
.then((_) {
runApp(new MyApp());
});
}
// wait for settings screen orientation after initiating app and -> then lock orientation
Important for iOS.
Enable the orientation in in info.plist file. for Example
Steps
Set the orientation in main.dart file. In my case, My application is only support for portrait except the one screen so i need to set the portrait mode at first time. for Example
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp,DeviceOrientation.portraitDown,]);
Add the following code in that screen which you need to rotate.
void initState() {
super.initState();
SystemChrome.setPreferredOrientations([
DeviceOrientation.landscapeRight,
DeviceOrientation.landscapeLeft,
]);
}
#override
dispose(){
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
]);
super.dispose();
}
Simple way to lock screen orientation in whole app
Add import 'package:flutter/services.dart'; to the start of main.dart file.
Create SystemChrome.setPreferredOrientations(); method to disable Screen rotation in Widget build area of MyApp class just before the return part.
Specify the orientation using [DeviceOrientation.<orientation-type>] in arguments of the method.
Use one of the following in place of <orientation-type> :
portraitUp
portraitDown
landscapeLeft
landscapeRight
Example Code:
import 'package:flutter/material.dart';
import 'package:flutter/services.dart' ;
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
]);
return MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text("Screen Orientation"),
),
body: Container(
),
),
);
}
}
import services.dart and your void main function should be like:
void main(){
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations(
[DeviceOrientation.portraitUp, DeviceOrientation.portraitDown])
.then((_){
runApp(MyApp());
}
);
}
You can use orientation_helper for this https://pub.dev/packages/orientation_helper . It’s main goal is to set orientation for each screen in an app.
For those who prefer to use hooks
import 'package:flutter/services.dart';
import 'package:flutter_hooks/flutter_hooks.dart';
useOrientation(List<DeviceOrientation> orientations) {
useEffect(
() {
SystemChrome.setPreferredOrientations(orientations);
return () {
SystemChrome.setPreferredOrientations([
DeviceOrientation.portraitUp,
DeviceOrientation.portraitDown,
DeviceOrientation.landscapeLeft,
DeviceOrientation.landscapeRight,
]);
};
},
);
}
Use it like:
class MyWidget extends HookWidget {
void build(BuildContext context) {
useOrientation([DeviceOrientation.portraitUp]);
return Container();
}
}
In AndroidManifest file in main folder under activity tag set android:screenOrientation = "portrait"
<activity android:windowSoftInputMode="adjustResize" android:screenOrientation = "portrait">
Set the preferred orientation in the flutter.
// import this package
import 'package:flutter/services.dart';
// Lock the orientation to Portrait Only
WidgetsFlutterBinding.ensureInitialized();
SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp])
.then((value) => runApp(MyApp()));
You can also add Preferred Orientations in the setPreferredOrientations list like [DeviceOrientation.portraitUp, DeviceOrientation.portraitDown]
Below are the orientation you can set:
/// If the device shows its boot logo in portrait, then the boot logo is shown
/// in [portraitUp]. Otherwise, the device shows its boot logo in landscape
/// and this orientation is obtained by rotating the device 90 degrees
/// clockwise from its boot orientation.
portraitUp,
/// The orientation that is 90 degrees clockwise from [portraitUp].
///
/// If the device shows its boot logo in landscape, then the boot logo is
/// shown in [landscapeLeft].
landscapeLeft,
/// The orientation that is 180 degrees from [portraitUp].
portraitDown,
/// The orientation that is 90 degrees counterclockwise from [portraitUp].
landscapeRight,
Ref: https://greymag.medium.com/flutter-orientation-lock-portrait-only-c98910ebd769
In GetX, you need to use GetBuilder like this example:
final Controller ctrl = Get.find();
GetBuilder<Controller>(
initState: (_) => ctrl.setLandscape(),
dispose: (_) => ctrl.setPortrait(),
builder: (code) => Container(
padding: const EdgeInsets.zero,
alignment: Alignment.Center,
child: const SizedBox(),
),
),
In Controller file:
class Controller extends GetxController {
RxBool isLandscape = false.obs;
Future<void> setLandscape() async {
if (isLandscape.isTrue) {
await SystemChrome.setPreferredOrientations([DeviceOrientation.landscapeLeft]);
update();
}
}
Future<void> setPortrait() async {
if (isLandscape.isFalse) {
await SystemChrome.setPreferredOrientations([DeviceOrientation.portraitUp]);
update();
}
}
}
I hope this solution will answer developers who use GetX as their main state management. Good luck, bro! God blesses you all.