Flutter: How to avoid asking for permissions from the system folder picker?

Question

I am using system folder picker to store my doc file, but whenever I am choosing folder then clicking on "USE THIS FOLDER" asking for permission.I want If I granted permission for any folder then dont ask permission for that perticular folder. Yes, If user select another folder repeat above conditions flow again.

I want If I allow One this permission then whenever come this page and click on "USE THIS FOLDER" don't ask again for that permissio thing.

I had used one this for it SharedPreferences but after using it I am not able to open the file selector again,Its giving me SharedPreferences previously saved folder. Let's assume that the user wants to select another folder, in this case this is going wrong.

use this Storage Access Framework

This is kotlin file code

import android.app.Activity
import android.content.ContentResolver
import android.content.Context
import android.content.Intent
import android.net.Uri
import android.os.Bundle
import android.util.Log
import androidx.annotation.NonNull
import io.flutter.embedding.android.FlutterActivity
import io.flutter.plugin.common.MethodCall
import io.flutter.plugin.common.MethodChannel

class MainActivity : FlutterActivity() {
    private val CHANNEL = "com.example.folder"
    private val REQUEST_CODE_OPEN_DOCUMENT_TREE = 1001
    private lateinit var sharedPreferences: android.content.SharedPreferences
    private var resultCallback: MethodChannel.Result? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        sharedPreferences = getSharedPreferences("folder_picker_prefs", Context.MODE_PRIVATE)

        // Ensure flutterEngine and dartExecutor are non-null before initializing the MethodChannel
        val messenger = flutterEngine?.dartExecutor?.binaryMessenger
        if (messenger != null) {
            MethodChannel(messenger, CHANNEL).setMethodCallHandler { call, result ->
                resultCallback = result
                when (call.method) {
                    "pickOrGetFolder" -> handlePickOrGetFolder()
                    else -> result.notImplemented()
                }
            }
        } else {
            Log.e("MainActivity", "BinaryMessenger is null. Cannot initialize MethodChannel.")
        }
    }

    private fun handlePickOrGetFolder() {
        val savedUriString = sharedPreferences.getString("selected_folder_uri", null)

        if (savedUriString != null) {
            // Folder URI exists; check if permissions are still valid
            val savedUri = Uri.parse(savedUriString)
            val hasPermissions = contentResolver.persistedUriPermissions.any {
                it.uri == savedUri &&
                        it.isReadPermission &&
                        it.isWritePermission
            }

            if (hasPermissions) {
                // Permissions are valid, return the saved URI to Flutter
                resultCallback?.success(savedUriString)
            } else {
                // Permissions are missing; remove saved URI and ask for folder selection again
                sharedPreferences.edit().remove("selected_folder_uri").apply()
                openFolderPicker()
            }
        } else {
            // No folder URI exists; open folder picker for the first time
            openFolderPicker()
        }
    }

    private fun openFolderPicker() {
        val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE).apply {
            addFlags(
                Intent.FLAG_GRANT_READ_URI_PERMISSION or
                        Intent.FLAG_GRANT_WRITE_URI_PERMISSION or
                        Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
            )
        }
        startActivityForResult(intent, REQUEST_CODE_OPEN_DOCUMENT_TREE)
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        if (requestCode == REQUEST_CODE_OPEN_DOCUMENT_TREE && resultCode == Activity.RESULT_OK) {
            val uri = data?.data
            if (uri != null) {
                // Persist permissions for the selected folder
                contentResolver.takePersistableUriPermission(
                    uri,
                    Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                )
                // Save the folder URI persistently
                sharedPreferences.edit().putString("selected_folder_uri", uri.toString()).apply()

                // Return the folder URI to Flutter
                resultCallback?.success(uri.toString())
            } else {
                // If no folder was selected, return an error to Flutter
                resultCallback?.error("FOLDER_SELECTION_CANCELLED", "No folder was selected.", null)
            }
        }
    }
}

this is flutter code

class FolderPickerScreen extends StatefulWidget {
  @override
  _FolderPickerScreenState createState() => _FolderPickerScreenState();
}

class _FolderPickerScreenState extends State<FolderPickerScreen> {
  static const platform = MethodChannel('com.example.folder');
  String folderPath = "No folder selected.";

  Future<void> pickFolder() async {
    try {
      final String? result = await platform.invokeMethod('pickOrGetFolder');
      setState(() {
        folderPath = result ?? "No folder selected.";
      });
    } on PlatformException catch (e) {
      setState(() {
        folderPath = "Error: ${e.message}";
      });
    }
  }

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        appBar: AppBar(title: Text("Folder Picker")),
        body: Center(
          child: Column(
            mainAxisAlignment: MainAxisAlignment.center,
            children: [
              Text(folderPath),
              ElevatedButton(
                onPressed: pickFolder,
                child: Text("Pick Folder"),
              ),
            ],
          ),
        ),
      ),
    );
  }
}

in this code I am using sharedpreference but I dont want it, because using it I cant open Folder picker of system.

Answer 1

In order to handle per folder permissions, I think you should use Android's persistedUriPermissions API. This allows you to retrieve previously used folders, while also giving you the option to add new ones as the users use your app and grant relevant permissions.

Here is an example of the changes you can make to your flutter activity:

import android.app.Activity
import android.content.Intent
import android.net.Uri
import android.os.Bundle
import androidx.documentfile.provider.DocumentFile
import io.flutter.embedding.android.FlutterActivity
import io.flutter.plugin.common.MethodChannel

class MainActivity : FlutterActivity() {
    private val CHANNEL = "com.example.folder"
    private val REQUEST_CODE_OPEN_DOCUMENT_TREE = 1001
    private var resultCallback: MethodChannel.Result? = null

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)

        val messenger = flutterEngine?.dartExecutor?.binaryMessenger
        if (messenger != null) {
            MethodChannel(messenger, CHANNEL).setMethodCallHandler { call, result ->
                resultCallback = result
                when (call.method) {
                    "pickFolder" -> openFolderPicker()
                    "getPersistedFolders" -> getPersistedFolders(result)
                    "usePersistedFolder" -> usePersistedFolder(call.arguments as String, result)
                    else -> result.notImplemented()
                }
            }
        }
    }

    private fun openFolderPicker() {
        val intent = Intent(Intent.ACTION_OPEN_DOCUMENT_TREE).apply {
            addFlags(
                Intent.FLAG_GRANT_READ_URI_PERMISSION or
                Intent.FLAG_GRANT_WRITE_URI_PERMISSION or
                Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
            )
        }
        startActivityForResult(intent, REQUEST_CODE_OPEN_DOCUMENT_TREE)
    }

    private fun getPersistedFolders(result: MethodChannel.Result) {
        val persistedUris = contentResolver.persistedUriPermissions.map { permission ->
            mapOf(
                "uri" to permission.uri.toString(),
                "name" to (DocumentFile.fromTreeUri(this, permission.uri)?.name ?: "Unknown Folder")
            )
        }
        result.success(persistedUris)
    }

    private fun usePersistedFolder(uriString: String, result: MethodChannel.Result) {
        val uri = Uri.parse(uriString)
        val hasPermission = contentResolver.persistedUriPermissions.any {
            it.uri == uri && it.isReadPermission && it.isWritePermission
        }
        
        if (hasPermission) {
            result.success(uriString)
        } else {
            result.error("PERMISSION_DENIED", "No permission for this folder", null)
        }
    }

    override fun onActivityResult(requestCode: Int, resultCode: Int, data: Intent?) {
        super.onActivityResult(requestCode, resultCode, data)
        
        if (requestCode == REQUEST_CODE_OPEN_DOCUMENT_TREE && resultCode == Activity.RESULT_OK) {
            val uri = data?.data
            if (uri != null) {
                contentResolver.takePersistableUriPermission(
                    uri,
                    Intent.FLAG_GRANT_READ_URI_PERMISSION or Intent.FLAG_GRANT_WRITE_URI_PERMISSION
                )
                resultCallback?.success(uri.toString())
            } else {
                resultCallback?.error("FOLDER_SELECTION_CANCELLED", "No folder was selected.", null)
            }
        }
    }
}

If you want users to be able to select previously used folders, you can display them for example in an Expanded widget like so:

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class FolderPickerScreen extends StatefulWidget {
  @override
  _FolderPickerScreenState createState() => _FolderPickerScreenState();
}

class _FolderPickerScreenState extends State<FolderPickerScreen> {
  static const platform = MethodChannel('com.example.folder');
  String? selectedFolderUri;
  List<Map<String, dynamic>> persistedFolders = [];

  @override
  void initState() {
    super.initState();
    loadPersistedFolders();
  }

  Future<void> loadPersistedFolders() async {
    try {
      final List<dynamic> result = await platform.invokeMethod('getPersistedFolders');
      setState(() {
        persistedFolders = List<Map<String, dynamic>>.from(result);
      });
    } on PlatformException catch (e) {
      print("Error loading persisted folders: ${e.message}");
    }
  }

  Future<void> pickNewFolder() async {
    try {
      final String? result = await platform.invokeMethod('pickFolder');
      if (result != null) {
        setState(() {
          selectedFolderUri = result;
        });
        await loadPersistedFolders(); // Refresh the list
      }
    } on PlatformException catch (e) {
      print("Error picking folder: ${e.message}");
    }
  }

  Future<void> usePersistedFolder(String uri) async {
    try {
      final String? result = await platform.invokeMethod('usePersistedFolder', uri);
      if (result != null) {
        setState(() {
          selectedFolderUri = result;
        });
      }
    } on PlatformException catch (e) {
      print("Error using persisted folder: ${e.message}");
    }
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(title: Text("Folder Picker")),
      body: Column(
        children: [
          Padding(
            padding: const EdgeInsets.all(16.0),
            child: Text(
              "Selected Folder: ${selectedFolderUri ?? 'None'}",
              style: Theme.of(context).textTheme.bodyLarge,
            ),
          ),
          ElevatedButton(
            onPressed: pickNewFolder,
            child: Text("Pick New Folder"),
          ),
          if (persistedFolders.isNotEmpty) ...[
            Padding(
              padding: const EdgeInsets.all(16.0),
              child: Text(
                "Previously Selected Folders:",
                style: Theme.of(context).textTheme.titleMedium,
              ),
            ),
            Expanded(
              child: ListView.builder(
                itemCount: persistedFolders.length,
                itemBuilder: (context, index) {
                  final folder = persistedFolders[index];
                  return ListTile(
                    title: Text(folder['name'] as String),
                    subtitle: Text(folder['uri'] as String),
                    onTap: () => usePersistedFolder(folder['uri'] as String),
                  );
                },
              ),
            ),
          ],
        ],
      ),
    );
  }
}