Hi Yonglun, I have two questions below; #1 For Android version 11, is it possible to access /storage/emulated/0/ folder, and if yes, how to do it? #2 For Android version 11, is it possible to access some public storage, and how to do it? If it is possible, can you send the code? many thanks! Kevin

Android 11 external storage access

Accepted answer

Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 36,871 Microsoft Vendor

Hello,

#1 For Android version 11, is it possible to access /storage/emulated/0/ folder, and if yes, how to do it?

Android provides a special permission for this situation MANAGE_EXTERNAL_STORAGE to manage all files. However, if you use this dangerous permission, your program will not be able to publish to Google play.

Please refer to Manage all files on a storage device for more details.

#2 For Android version 11, is it possible to access some public storage, and how to do it?

For the use of public storage, Android provides two sets of access frameworks, when storing pictures, videos and other media files, Android provides MediaStore to CRUD operations on media files.

You could refe to the following code sample and documentation for more details.

// In this code example, by using MediaStore, you can save a picture to the relativePath folder under the album.
if (Build.VERSION.SdkInt >= BuildVersionCodes.Q)
{
	var contentValues = new ContentValues();
	contentValues.Put(MediaStore.IMediaColumns.DisplayName, "test.png");
	contentValues.Put(MediaStore.Files.IFileColumns.MimeType, "image/png");
	contentValues.Put(MediaStore.IMediaColumns.RelativePath, "Pictures/relativePath");
	try
	{
		var uri = MainActivity.Instance.ContentResolver.Insert(MediaStore.Images.Media.ExternalContentUri, contentValues);
		var output = MainActivity.Instance.ContentResolver.OpenOutputStream(uri);
		// This img variable is a byte array from an image.
		output.Write(img, 0, img.Length);
		output.Flush();
		output.Close();
	}
	catch (System.Exception ex)
	{
		Console.Write(ex.ToString());
	}
	contentValues.Put(MediaStore.IMediaColumns.IsPending, 1);
}

Access media files from shared storage.

For non-media files, Android provides the Storage Access Framework to access them. Please refer to the following documentation:

Access documents and other files from shared storage.

In Xamarin, you could use Storage Access Framework directly through FilePicker.

Best Regards,

Alec Liu.

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Lou, Kecheng 60 Reputation points

2023-06-28T13:29:59.1666667+00:00

Hi Alex,

Can you provide sample code for my question #1?

Kevin
Lou, Kecheng 60 Reputation points

2023-06-28T13:33:36.7666667+00:00

Lou, Kecheng 60

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" android:versionCode="1" android:versionName="1.0" package="com.companyname.app1" android:installLocation="auto">
	<uses-sdk android:minSdkVersion="21" android:targetSdkVersion="33" />
	<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" />
	<uses-permission android:name="android.permission.DEFAULT_SCOPED_STORAGE" />
	<uses-permission android:name="android.permission.FORCE_ENABLE_SCOPED_STORAGE" />
	<application android:allowBackup="true" android:icon="@mipmap/ic_launcher" android:label="@string/app_name" android:supportsRtl="true" android:theme="@style/AppTheme"></application>
</manifest>

Lou, Kecheng 60

using Android.App;
using Android.OS;
using Android.Runtime;
using Android.Widget;
using AndroidX.AppCompat.App;
using System;
using System.IO;
using System.Threading.Tasks;
using Xamarin.Essentials;
 
namespace App1
{
    [Activity(Label = "@string/app_name", Theme = "@style/AppTheme", MainLauncher = true)]
    public class MainActivity : AppCompatActivity
    {
        private Button saveButton;
        protected override void OnCreate(Bundle savedInstanceState)
        {
            base.OnCreate(savedInstanceState);
            SetContentView(Resource.Layout.activity_main);
            Xamarin.Essentials.Platform.Init(this, savedInstanceState);
            saveButton = FindViewById<Button>(Resource.Id.buttonSaveRec);
            saveButton.Click += SaveButton_Click;

            var status = CheckAndRequestLocationPermission();

        }
        private void SaveButton_Click(object sender, EventArgs e)
        {
            // Check if external storage is available
            if (Android.OS.Environment.ExternalStorageState == Android.OS.Environment.MediaMounted)
            {
                // Get the path to external storage directory
                var path = Android.OS.Environment.ExternalStorageDirectory.Path;
                //var path = GetExternalFilesDir(null).Path;

                var directoryName = "MyDirectory";
                var directoryPath = Path.Combine(path, directoryName);
                Directory.CreateDirectory(directoryPath);

                var fileName = "MyFile.txt";
                var filePath = Path.Combine(directoryPath, fileName);

                // Write some text to the file
                using (var streamWriter = new StreamWriter(filePath))
                {
                    streamWriter.Write("Hello World!");
                }

                Toast.MakeText(this, "File saved successfully", ToastLength.Short).Show();
            }
            else
            {
                Toast.MakeText(this, "External storage not available", ToastLength.Short).Show();
            }
        }
        public override void OnRequestPermissionsResult(int requestCode, string[] permissions, [GeneratedEnum] Android.Content.PM.Permission[] grantResults)
        {
            Xamarin.Essentials.Platform.OnRequestPermissionsResult(requestCode, permissions, grantResults);

            base.OnRequestPermissionsResult(requestCode, permissions, grantResults);
        }

        public async Task<PermissionStatus> CheckAndRequestLocationPermission()
        {
            var status = await Permissions.CheckStatusAsync<Permissions.LocationWhenInUse>();

            if (status == PermissionStatus.Granted)
                return status;

            if (status == PermissionStatus.Denied && DeviceInfo.Platform == DevicePlatform.iOS)
            {
                // Prompt the user to turn on in settings
                // On iOS once a permission has been denied it may not be requested again from the application
                return status;
            }

            if (Permissions.ShouldShowRationale<Permissions.LocationWhenInUse>())
            {
                // Prompt the user with additional information as to why the permission is needed
            }

            status = await Permissions.RequestAsync<Permissions.LocationWhenInUse>();

            return status;
        }

    }
}

Lou, Kecheng 60 Reputation points

2023-06-28T13:35:41.9066667+00:00

for some reason, I could not post all of above once time, sorry for it.
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 36,871 Reputation points Microsoft Vendor

2023-06-29T08:04:23.92+00:00

This is because MANAGE_EXTERNAL_STORAGE is a dangerous permission, so Android only allows you to apply for it while the program is running.

Please refer to the answer in How to Request manage_external_storage Permission in Xamarin.Android for more details.
Lou, Kecheng 60 Reputation points

2023-06-29T16:05:38.8966667+00:00

Hi Yonglun,

It works.

When the app runs at the first time, it shows message to notify the user grand the access for the app. it works perfectly.

However in our case, we have 50 android scanners, every time users run the app, they need to grand the accesses, it seems it is time consuming job (the plant users told me). Is it possible to skip this step, "automatically grand the access"?

MANY THANKS!!

Kevin
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 36,871 Reputation points Microsoft Vendor

2023-06-30T01:39:47.2633333+00:00

This is not possible, as mentioned earlier, MANAGE_EXTERNAL_STORAGE is a dangerous permission, so the Android system has made restrictions on the permission that must be manually opened by the user.

This is due to the limitations of the Android system layer, so the automatic application of this permission cannot be realized.
Lou, Kecheng 60 Reputation points

2023-06-30T13:27:44.65+00:00

Thanks Yonglun, I do appreicate your help!
Yonglun Liu (Shanghai Wicresoft Co,.Ltd.) 36,871 Reputation points Microsoft Vendor

2023-07-03T02:34:55.9833333+00:00

Thanks for your feedback.

Could you please accept this answer?

This will help people who will experience the same problem in the community in the future.

You could refer to Accept an answer on Microsoft Q&A for more details.

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Android 11 external storage access

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