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OS Error: Operation not permitted, errno = 1) even with MANAGE_EXTERNAL_STORAGE

I have an application that generates some PDFs and CSV files and at the moment I am saving these files into the files folder in the application directory of the Android phone. Then the user needs to manually move the files to another folder (for example Documents or Downloads).
I would like to save the file to the Documents or Download folder (one of the two, is the same) automatically at runtime, after the files are generated by the app. The target devices has Android 11 so I have any kind of problems with managing the external storage.
Android Manifest:
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.app.example">
<!-- PERMISSIONS -->
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE"/>
...
...
Permissions requested at startup:
requestPermissions() async {
try {
await [
Permission.storage,
Permission.manageExternalStorage,
].request();
} catch (e) {
LoggerService().error("PERMISSIONS REQUEST ERROR", e.toString());
}
}
Method that saves the files:
Future<String> export(Uint8List pdf, {String? fileName}) async {
Directory dir = Directory(EnvironmentService.documentsPath);
String path = "${dir.path}/${fileName ?? "${uuid.v4()}.pdf"}";
File file = File(path);
await file.writeAsBytes(pdf);
return path;
}
Path where I am trying to save the files:
static const String documentsPath = "/storage/emulated/0/Documents";
When saving the file I always get OS Error: Operation not permitted, errno = 1) error, even if I have granted the MANAGE_EXTERNAL_STORAGE permission. The application will not be published on the Play Store, and needs to be working only on Android.
Any idea of what's happening?

Android 11 Permission Issue

my flutter code is
var storageInfo = await PathProviderEx.getStorageInfo();
var root = storageInfo[0]
.rootDir;
var fm = FileManager(root: Directory(root));
await fm.filesTree(
excludedPaths: [
'/storage/emulated/0/Android',
],
extensions: ['pdf']
);
error occur
E/flutter (16591): FileSystemException: Directory listing failed, path = '/storage/emulated/0/Android/obb' (OS Error: Permission denied, errno = 13)
E/flutter (16591): #0 FileManager.dirsTree (package:flutter_file_manager/src/file_manager.dart:110:7)
E/flutter (16591): #1 FileManager.filesTree (package:flutter_file_manager/src/file_manager.dart:132:34)
I have one issue to get list of files from stroage in android 11 from Flutter app
i already add both permission in AndroidManifest.xml file
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

We need to request manage_external_storage permission via permission_handler.
Add this permission to AndroidManifest.xml
<uses-permission android:name="android.permission.MANAGE_EXTERNAL_STORAGE" />
Request permission as shown below
await Permission.manageExternalStorage.request();
Then we can read any file and write to any location in Android 11.

The right solution will be to add android:requestLegacyExternalStorage="true" to your AndroidManifest file and in build.gradle change targetSdkVersion 29 whereas keeping compileSdkVersion 30. This should work fine.

Request write permission for SD Card

I am trying to write data to the SD card for android using the permission_handler package but it seems that PermissionGroup.storage only request permission for internal storage. Is what I'm trying to do possible?
This is the my code for requesting permission:
Future<bool> _checkPermission() async {
PermissionStatus permission = await Permission.storage.status;
print(permission);
if (permission != PermissionStatus.granted) {
if (await Permission.storage.request().isGranted) {
return true;
}
} else {
return true;
}
return false;
}
And this is the error I get when I try to create a folder on the sd card.
PS: This works for internal storage
Unhandled Exception: FileSystemException: Creation failed, path = '/storage/1EFF-130C/Music/2020' (OS Error: Permission denied, errno = 13)

Micro SD cards are read only on modern Android devices.
Only one app specific directory is writable.
On Android Q+ the card is not even readable except for that directory.
You can however use SAF for full access.

How do I allow public access to my apps data folder on the android sdcard

I am writing a flutter app for Android devices. I want to be able to access my apps data folder from my PC using windows explorer so I can copy data into it that my app can use. I can see the folder has been created correctly by my app when I view the sdcard folder within android studio, but not when I view the data folder using windows explorer.
I am guessing this is a permissions issue, but am not sure.
I am using path provider 1.5.1 and permission handler 4.0.0
Here is how I am getting permission to read/write from my folder:
Future<void> getPermission() async {
String path;
if (Platform.isAndroid) {
PermissionStatus permission = await PermissionHandler().checkPermissionStatus(PermissionGroup.storage);
if (permission != PermissionStatus.granted) {
await PermissionHandler().requestPermissions([PermissionGroup.storage]);
}
path = (await getExternalStorageDirectory()).path;
} else if (Platform.isIOS) {
// to be written....
}
}
I have added these lines to my AndroidManifest.xml file
<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
Can someone point me in the right direction please?

fopen failed while writing into an external SDcard in Android native code

When I am trying to write into external SDcard from android native code, I am getting permission denied in fopen.
mFp = fopen("/storage/extSdCard/Output/test.txt", "wb");
if I print strerror(errno) it gives ->
fopen(/storage/extSdCard/Output/test.txt) failed: Permission denied
Please note that I have also given the permissions in my Application manifest :
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
....
</manifest>
and also :
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
return true;
}
is returing true.

Please check if the external storage is an external card that is inserted or the sdcard that comes with the device.If it is an sdcard that comes with the device itself try your path as "/mnt/drive_path" and check if you native method is able to write to your storage.