Develop Reference

Flutter `Screenshot` package: Why isn't the `captureAndSave()` method saving an image to my (Android) device?

Preface:
I'm using the Screenshot package. In this package, there is a method captureAndSave() which saves a widget as an image to a specific location, however, when I call this function, my image is not being saved. Why?
Complete Code Example:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:qr_flutter/qr_flutter.dart';
import 'package:screenshot/screenshot.dart';
class QrCodeScreen extends StatefulWidget {
const QrCodeScreen({Key? key}) : super(key: key);
#override
State<QrCodeScreen> createState() => _QrCodeScreenState();
}
class _QrCodeScreenState extends State<QrCodeScreen> {
final _screenshotController = ScreenshotController();
Image? image;
var doesTheImageExist = false;
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
if (image == null)
TextButton(
child: Text("Save QR Code"),
onPressed: () async {
await _captureAndSaveQRCode();
image = await _loadImage();
setState(() {});
},
)
else
image!,
Text("Is the QR Code saved to your device? ${doesTheImageExist}"),
if (image == null)
Screenshot(
controller: _screenshotController,
child: _buildQRImage('_authProvider.user!.uid')),
],
),
);
}
Widget _buildQRImage(String data) {
return QrImage(
data: data,
size: 250.0,
gapless: false,
foregroundColor: Colors.black,
backgroundColor: Colors.white,
);
}
Future<String> get imagePath async {
final directory = (await getApplicationDocumentsDirectory()).path;
return '$directory/qr.png';
}
Future<Image> _loadImage() async {
return imagePath.then((imagePath) => Image.asset(imagePath));
}
Future<void> _captureAndSaveQRCode() async {
final path = await imagePath;
await _screenshotController.captureAndSave(path);
// It always returns false, although I'm saving the file using `captureAndSave` .
doesTheImageExist = File(path).existsSync();
}
}
The Question:
In the code above, when I click on the TextButton() that says "Save QR Code" it then calls _captureAndSaveQRCode() and _loadImage(). Hence my image should successfully be saved to my (Android) phone. However, I get an error:
Unable to load asset: /data/user/0/com.example.qr/app_flutter/qr.png
Full Traceback:
======== Exception caught by image resource service ================================================
The following assertion was thrown resolving an image codec:
Unable to load asset: /data/user/0/com.example.qr/app_flutter/qr.png
When the exception was thrown, this was the stack:
#0 PlatformAssetBundle.load (package:flutter/src/services/asset_bundle.dart:237:7)
<asynchronous suspension>
#1 AssetBundleImageProvider._loadAsync (package:flutter/src/painting/image_provider.dart:675:14)
<asynchronous suspension>
Image provider: AssetImage(bundle: null, name: "/data/user/0/com.example.qr/app_flutter/qr.png")
Image key: AssetBundleImageKey(bundle: PlatformAssetBundle#5986d(), name: "/data/user/0/com.example.qr/app_flutter/qr.png", scale: 1.0)
====================================================================================================
Why isn't my image being saved to the device when calling _captureAndSaveQRCode()?
Side note:
I recently posted an answer (currently in Bounty) with (almost) the same code as in this question which does work correctly, so, what's the difference?

The problem was that I had an empty setState:
onPressed: () async {
await _captureAndSaveQRCode();
image = await _loadImage();
setState(() {});
},
)
So to solve the problem, I removed the setState and also got rid of the _loadImage() function.
And then updated the image variable within the TextButton():
TextButton(
child: Text("Save QR Code"),
onPressed: () async {
await _captureAndSaveQRCode();
setState(() {
doesTheImageExist = true;
image = image;
});
},
)
Complete working example:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:path_provider/path_provider.dart';
import 'package:qr_flutter/qr_flutter.dart';
import 'package:screenshot/screenshot.dart';
class QrCodeScreen extends StatefulWidget {
const QrCodeScreen({Key? key}) : super(key: key);
#override
State<QrCodeScreen> createState() => _QrCodeScreenState();
}
class _QrCodeScreenState extends State<QrCodeScreen> {
final _screenshotController = ScreenshotController();
Image? image;
var doesTheImageExist = false;
#override
Widget build(BuildContext context) {
return Scaffold(
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
if (image == null)
TextButton(
child: Text("Save QR Code"),
onPressed: () async {
await _captureAndSaveQRCode();
setState(() {
doesTheImageExist = true;
image = image;
});
},
)
else
image!,
Row(children: [
Text('hi'),
Text("Is the QR Code saved to your device? ${doesTheImageExist}")
]),
if (image == null)
Screenshot(
controller: _screenshotController,
child: _buildQRImage('_authProvider.user!.uid')),
],
),
);
}
Widget _buildQRImage(String data) {
return QrImage(
data: data,
size: 250.0,
gapless: false,
foregroundColor: Colors.black,
backgroundColor: Colors.white,
);
}
Future<String> get imagePath async {
final directory = (await getApplicationDocumentsDirectory()).path;
return '$directory/qr.png';
}
// Future<Image> _loadImage() async {
// return imagePath.then((imagePath) => Image.asset(imagePath));
// }
Future<void> _captureAndSaveQRCode() async {
final path = await imagePath;
await _screenshotController.captureAndSave(path);
// It always returns false, although I'm saving the file using `captureAndSave` .
doesTheImageExist = File(path).existsSync();
}
}

load image with Image.file(File(imagePath))
Image.Asset is for loading images defined in pubspec.yaml
Edit:
the path in captureAndSave is directory path. it takes another optional argument fileName.
// previous code
// i create new getter for directory
Future<String> get dirPath async {
final directory = (await getApplicationDocumentsDirectory()).path;
return directory;
}
Future<String> get imagePath async {
final directory = await dirPath;
return '$directory/qr.png';
}
Future<Image> _loadImage() async {
return imagePath.then((imagePath) => Image.file(File(imagePath)));
}
Future<void> _captureAndSaveQRCode() async {
final path = await dirPath;
await _screenshotController.captureAndSave(path, fileName: "qr.png");
// It always returns false, although I'm saving the file using `captureAndSave` .
doesTheImageExist = File(path).existsSync();
}
// the rest of the code

Flutter - sharing files from application's document directory gives IllegalArguementException

I am trying to share a file using SharePlus. However, I get the following error:
The task is to generate a PDF file and share it through ios and android. I see that share_plus is able to share the file. However, I am unable to share by saving it in the applicationDocumentDirectory.
Update: I have attached a demo repo with codes from below. The error is showing in my app even when the repo is working without permissions fine. share_plus complains with below issues.
Repo: Link
Error:
Unhandled Exception: PlatformException(error, Failed to find configured root that contains /data/user/0/com.example.flutter_share_demo/app_flutter/someRandom.pdf, null, java.lang.IllegalArgumentException: Failed to find configured root that contains /data/user/0/com.example.flutter_share_demo/app_flutter/someRandom.pdf
The code is as follows:
import 'dart:io';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:path_provider/path_provider.dart';
import 'package:pdf/widgets.dart' as pw;
import 'package:permission_handler/permission_handler.dart';
import 'package:share_plus/share_plus.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
home: const MyHomePage(),
);
}
}
class MyHomePage extends StatelessWidget {
const MyHomePage({
Key? key,
}) : super(key: key);
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(title: const Text('Share files')),
body: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: [
Center(
child: TextButton(
child: const Text('Generate and Share PDF'),
onPressed: () async {
final pdf = pw.Document();
pdf.addPage(pw.Page(
build: (context) =>
pw.Center(child: pw.Text('Hello, World!')),
));
final Directory storageDir = getApplicationDocumentDirectory();
try {
File file = File('${storageDir.path}/someRandom.pdf');
await file.writeAsBytes(await pdf.save());
print(file.path);
print('File exists: ${await file.exists()}');
Share.shareFiles([file.path], subject: 'Shared file');
} else {
ScaffoldMessenger.of(context).showSnackBar(
const SnackBar(content: Text('Permission denied')));
}
} on PlatformException catch (ex) {
print(ex);
} catch (ex) {
print(ex);
}
},
),
),
],
));
}
}

Flutter: Adding App Update Dialog for iOS and Android

I am currently working on Notification Feature so when a new Update is availible the User gets a Dialog where he can choose to Update or not. I'm doing it with Firebase Remote Config where i have a Parameter called "force_update_current_version" where i then add the Value for the Version for checking. But I do get following errors.
Thanks for your help and i wish you a healty start into the new Year.
Main.dart Code
import 'checkUpdate.dart';
#override
void initState() {
try {
versionCheck(**context**);
} catch (e) {
print(e);
}
**super**.initState();
}
context error: Undefined name 'context'.
Try correcting the name to one that is defined, or defining the name.
super error: Invalid context for 'super' invocation.
checkUpdate.dart Code
import 'package:flutter/material.dart';
import 'dart:io';
import 'package:firebase_remote_config/firebase_remote_config.dart';
import 'package:url_launcher/url_launcher.dart';
import 'package:package_info/package_info.dart';
import 'package:flutter/cupertino.dart';
const APP_STORE_URL = 'https://apps.apple.com/us/app/appname/idAPP-ID';
const PLAY_STORE_URL =
'https://play.google.com/store/apps/details?id=APP-ID';
versionCheck(context) async {
//Get Current installed version of app
final PackageInfo info = await PackageInfo.fromPlatform();
double currentVersion = double.parse(info.version.trim().replaceAll(".", ""));
//Get Latest version info from firebase config
final RemoteConfig remoteConfig = await RemoteConfig.instance;
try {
// Using default duration to force fetching from remote server.
await remoteConfig.fetch(expiration: const Duration(seconds: 0));
await remoteConfig.activateFetched();
remoteConfig.getString('force_update_current_version');
double newVersion = double.parse(remoteConfig
.getString('force_update_current_version')
.trim()
.replaceAll(".", ""));
if (newVersion > currentVersion) {
_showVersionDialog(context);
}
} on FetchThrottledException catch (exception) {
// Fetch throttled.
print(exception);
} catch (exception) {
print('Unable to fetch remote config. Cached or default values will be '
'used');
}
}
//Show Dialog to force user to update
_showVersionDialog(context) async {
await showDialog<String>(
context: context,
barrierDismissible: false,
builder: (BuildContext context) {
String title = "New Update Available";
String message =
"There is a newer version of app available please update it now.";
String btnLabel = "Update Now";
String btnLabelCancel = "Later";
return Platform.isIOS
? new CupertinoAlertDialog(
title: Text(title),
content: Text(message),
actions: <Widget>[
FlatButton(
child: Text(btnLabel),
onPressed: () => _launchURL(**Config**.APP_STORE_URL),
),
FlatButton(
child: Text(btnLabelCancel),
onPressed: () => Navigator.pop(context),
),
],
)
: new AlertDialog(
title: Text(title),
content: Text(message),
actions: <Widget>[
FlatButton(
child: Text(btnLabel),
onPressed: () => _launchURL(**Config**.PLAY_STORE_URL),
),
FlatButton(
child: Text(btnLabelCancel),
onPressed: () => Navigator.pop(context),
),
],
);
},
);
}
_launchURL(String url) async {
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could not launch $url';
}
}
Config Error for App and Play Store: Undefined name 'Config'.
Try correcting the name to one that is defined, or defining the name.

In checkUpdate.dart we need to import the firebase_remote_config package that exposes the RemoteConfig class:
import 'package:firebase_remote_config/firebase_remote_config.dart';
Make sure to install it before.
The versionCheck() function shall be invoked from a StatefulWidget, hence, a good place to call it would be inside the first screen Widget, for example:
class FirstScreen extends StatefulWidget {
const FirstScreen({ Key key }) : super(key: key);
#override
_FirstScreenState createState() => _FirstScreenState();
}
class _FirstScreenState extends State<FirstScreen> {
#override
void initState() {
super.initState();
WidgetsBinding.instance
.addPostFrameCallback((_) => versionCheck(context));
}
#override
Widget build(BuildContext context) {
return Container(color: const Color(0xFFFFE306));
}
}

How to open PPTs, PDFs, docs, etc. using default applicaitions by tapping on a button in a Flutter app?

I am trying to make an app which opens up a PPT, PDF or Docx file using the default application on the device by tapping on a button in my application. If there is no default app, it should open the "Open With" menu.
I tried to use open_file. But it didn't work. I also tried a few other methods I saw on StackOverflow, but none of them worked for me.

To open file on Internet you can use package https://pub.dev/packages/url_launcher
code snippet for url_launcher
import 'package:flutter/material.dart';
import 'package:url_launcher/url_launcher.dart';
void main() {
runApp(Scaffold(
body: Center(
child: RaisedButton(
onPressed: _launchURL,
child: Text('Open File'),
),
),
));
}
_launchURL() async {
const url = 'https://yoursite/sample.pdf';
if (await canLaunch(url)) {
await launch(url);
} else {
throw 'Could not launch $url';
}
}
To open file in local path
You can see working demo and full code below
code snippet
final filePath = '/sdcard/Download/sample.pdf';
print('${filePath}');
final message = await OpenFile.open(filePath);
full code
import 'package:flutter/material.dart';
import 'dart:async';
import 'package:open_file/open_file.dart';
void main() => runApp(new MyApp());
class MyApp extends StatefulWidget {
#override
_MyAppState createState() => new _MyAppState();
}
class _MyAppState extends State<MyApp> {
String _openResult = 'Unknown';
Future<void> openFile() async {
final filePath = '/sdcard/Download/sample.pdf';
print('${filePath}');
final message = await OpenFile.open(filePath);
setState(() {
_openResult = message;
});
}
#override
Widget build(BuildContext context) {
return new MaterialApp(
home: new Scaffold(
appBar: new AppBar(
title: const Text('Plugin example app'),
),
body: Center(
child: Column(
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text('open result: $_openResult\n'),
FlatButton(
child: Text('Tap to open file'),
onPressed: openFile,
),
],
),
),
),
);
}
}
Emulator SDCard Download directory has a pdf file
working demo

How to get files from external storage in Flutter?

I want to get all file in listview with flutter project but how to access the external folder.
I have created a folder with name 'MyFile' and it is created at "/storage/emulated/0/MyFile",
but below code pointing at "/storage/emulated/0/Android/data/com.example.demo/MyFile".
I don't know why below code is not working
Directory externalDirectory = await getExternalStorageDirectory();
print('External Storage:$externalDirectory');
// External storage: /storage/emulated/0/Android/data/com.example.demo/MyFile

When using Flutter Official path_provider package, getExternalStorageDirectory() will always return path to /storage/emulated/0/your-package-name/files.
To get /storage/emulated/0/, you can used a Third-party package ext_storage. Below code will return your desired Directory path
var externalDirectoryPath = await ExtStorage.getExternalStorageDirectory();
print(path); // /storage/emulated/0
Now to create a Folder, you can use the below function:
//this will create a Folder in the storage/emulated/0
new Directory(externalDirectoryPath +'/YourfolderName')
.create()
.then((Directory directory)
{
print(directory.path);
});;
'

Edit post picture 2 to prove it work.
code snippet to create directory , file
new Directory('/storage/emulated/0/MyFile').create()
// The created directory is returned as a Future.
.then((Directory directory) {
print(directory.path);
});
new File('/storage/emulated/0/MyFile/test.txt').create(recursive: true)
.then((File file) {
// Stuff to do after file has been created...
print('${file.path}');
});
var dir = Directory('/storage/emulated/0/MyFile');
print('${dir.path}');
print('${dir.list().toList()}');
full code for create directory and file
import 'package:flutter/material.dart';
import 'dart:io';
import 'package:simple_permissions/simple_permissions.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
// This widget is the root of your application.
#override
Widget build(BuildContext context) {
return MaterialApp(
title: 'Flutter Demo',
theme: ThemeData(
// This is the theme of your application.
//
// Try running your application with "flutter run". You'll see the
// application has a blue toolbar. Then, without quitting the app, try
// changing the primarySwatch below to Colors.green and then invoke
// "hot reload" (press "r" in the console where you ran "flutter run",
// or simply save your changes to "hot reload" in a Flutter IDE).
// Notice that the counter didn't reset back to zero; the application
// is not restarted.
primarySwatch: Colors.blue,
),
home: MyHomePage(title: 'Flutter Demo Home Page'),
);
}
}
class MyHomePage extends StatefulWidget {
MyHomePage({Key key, this.title}) : super(key: key);
// This widget is the home page of your application. It is stateful, meaning
// that it has a State object (defined below) that contains fields that affect
// how it looks.
// This class is the configuration for the state. It holds the values (in this
// case the title) provided by the parent (in this case the App widget) and
// used by the build method of the State. Fields in a Widget subclass are
// always marked "final".
final String title;
#override
_MyHomePageState createState() => _MyHomePageState();
}
class _MyHomePageState extends State<MyHomePage> {
int _counter = 0;
void _incrementCounter() {
new Directory('/storage/emulated/0/MyFile').create()
// The created directory is returned as a Future.
.then((Directory directory) {
print(directory.path);
});
new File('/storage/emulated/0/MyFile/test.txt').create(recursive: true)
.then((File file) {
// Stuff to do after file has been created...
print('${file.path}');
});
var dir = Directory('/storage/emulated/0/MyFile');
print('${dir.path}');
print('${dir.list().toList()}');
setState(() {
// This call to setState tells the Flutter framework that something has
// changed in this State, which causes it to rerun the build method below
// so that the display can reflect the updated values. If we changed
// _counter without calling setState(), then the build method would not be
// called again, and so nothing would appear to happen.
_counter++;
});
}
#override
Widget build(BuildContext context) {
SimplePermissions.requestPermission(Permission.WriteExternalStorage);
// This method is rerun every time setState is called, for instance as done
// by the _incrementCounter method above.
//
// The Flutter framework has been optimized to make rerunning build methods
// fast, so that you can just rebuild anything that needs updating rather
// than having to individually change instances of widgets.
return Scaffold(
appBar: AppBar(
// Here we take the value from the MyHomePage object that was created by
// the App.build method, and use it to set our appbar title.
title: Text(widget.title),
),
body: Center(
// Center is a layout widget. It takes a single child and positions it
// in the middle of the parent.
child: Column(
// Column is also a layout widget. It takes a list of children and
// arranges them vertically. By default, it sizes itself to fit its
// children horizontally, and tries to be as tall as its parent.
//
// Invoke "debug painting" (press "p" in the console, choose the
// "Toggle Debug Paint" action from the Flutter Inspector in Android
// Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
// to see the wireframe for each widget.
//
// Column has various properties to control how it sizes itself and
// how it positions its children. Here we use mainAxisAlignment to
// center the children vertically; the main axis here is the vertical
// axis because Columns are vertical (the cross axis would be
// horizontal).
mainAxisAlignment: MainAxisAlignment.center,
children: <Widget>[
Text(
'You have pushed the button this many times:',
),
Text(
'$_counter',
style: Theme.of(context).textTheme.display1,
),
],
),
),
floatingActionButton: FloatingActionButton(
onPressed: _incrementCounter,
tooltip: 'Increment',
child: Icon(Icons.add),
), // This trailing comma makes auto-formatting nicer for build methods.
);
}
}
please use package flutter_file_manager https://pub.dev/packages/flutter_file_manager
I have tested with real device, it works fine
full code
// framework
import 'dart:async';
import 'dart:io';
import 'package:flutter/material.dart';
// packages
import 'package:flutter_file_manager/flutter_file_manager.dart';
import 'package:path_provider/path_provider.dart';
import 'package:path/path.dart' as p;
import 'package:simple_permissions/simple_permissions.dart';
void main() => runApp(new MyApp());
#immutable
class MyApp extends StatelessWidget {
#override
Widget build(BuildContext context) {
//SimplePermissions.requestPermission(Permission.ReadExternalStorage);
SimplePermissions.requestPermission(Permission.WriteExternalStorage);
return new MaterialApp(
home: Scaffold(
appBar: AppBar(
title: Text("Flutter File Manager Demo"),
),
body: FutureBuilder(
future: _files(), // a previously-obtained Future<String> or null
builder: (BuildContext context, AsyncSnapshot snapshot) {
switch (snapshot.connectionState) {
case ConnectionState.none:
return Text('Press button to start.');
case ConnectionState.active:
case ConnectionState.waiting:
return Text('Awaiting result...');
case ConnectionState.done:
if (snapshot.hasError)
return Text('Error: ${snapshot.error}');
return snapshot.data != null
? ListView.builder(
itemCount: snapshot.data.length,
itemBuilder: (context, index) => Card(
child: ListTile(
title: Column(children: [
Text('Size: ' +
snapshot.data[index]
.statSync()
.size
.toString()),
Text('Path: ' +
snapshot.data[index].path.toString()),
Text('Date: ' +
snapshot.data[index]
.statSync()
.modified
.toUtc()
.toString())
]),
subtitle: Text(
"Extension: ${p.extension(snapshot.data[index].absolute.path).replaceFirst('.', '')}"), // getting extension
)))
: Center(
child: Text("Nothing!"),
);
}
return null; // unreachable
},
)),
);
}
_files() async {
var root = await getExternalStorageDirectory();
var files = await FileManager(root: root).walk().toList();
for(var i = 0;i<files.length;i++) {
print("${files[i].path} ");
}
return files;
}
}
working demo in emulator

I had the same problem, while Android SDK version >30 or 31 doesn't allow to read from other directories but you definitely read from your directory without any permission.
Add '//' + directory path & your problem will be resolved
So it means that your path will be '//'+ getExternalStorageDirectory())!.path
This is the code to save and retrieve the file work on both SDK > 30 and SDK =< 30.
final directory = (await getExternalStorageDirectory())!.path;
ByteData? byteData =
await (image.toByteData(format: ui.ImageByteFormat.png));
Uint8List pngBytes = byteData!.buffer.asUint8List();
File imgFile = new File('$directory/screenshot${rng.nextInt(2000)}.png');
await imgFile.writeAsBytes(pngBytes);
setState(() {
_imageFile = imgFile;
});
// Add '//' + directory path & your problem will be resolved
return '//'+imgFile.path;
First I'm saving the image in the directory then I'm reading it.