What permissions do I need to download files?

Question

I am trying to download a file using the DownloadManager class.

public void downloadFile(View view) {

    String urlString = "your_url_here";
    try {
        // Get file name from the url
        String fileName = urlString.substring(urlString.lastIndexOf("/") + 1);
        // Create Download Request object
        DownloadManager.Request request = new DownloadManager.Request(Uri.parse((urlString)));
        // Display download progress and status message in notification bar
        request.setNotificationVisibility(Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
        // Set description to display in notification
        request.setDescription("Download " + fileName + " from " + urlString);
        // Set title
        request.setTitle("DownloadManager");
        // Set destination location for the downloaded file
        request.setDestinationUri(Uri.parse("file://" + Environment.getExternalStorageDirectory() + "/" + fileName));
        // Download the file if the Download manager is ready
        did = dManager.enqueue(request);

    } catch (Exception e) {
    }
}

// BroadcastReceiver to receive intent broadcast by DownloadManager
private BroadcastReceiver downloadReceiver = new BroadcastReceiver() {

    @Override
    public void onReceive(Context arg0, Intent arg1) {
        // TODO Auto-generated method stub
        Query q = new Query();
        q.setFilterById(did);
        Cursor cursor = dManager.query(q);
        if (cursor.moveToFirst()) {
            String message = "";
            int status = cursor.getInt(cursor.getColumnIndex(DownloadManager.COLUMN_STATUS));
            if (status == DownloadManager.STATUS_SUCCESSFUL) {
                message = "Download successful";
            } else if (status == DownloadManager.STATUS_FAILED) {
                message = "Download failed";
            }
            tvMessage.setText(message);
        }


    }
};

I am using dexter to obtain permissions

 Dexter.withActivity(this)
                .withPermission(Manifest.permission.READ_EXTERNAL_STORAGE)
                .withListener(new PermissionListener() {
                    @Override
                    public void onPermissionGranted(PermissionGrantedResponse response) {

I also have both in my manifest

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

But I still get this error while trying to download files (ONLY on Oreo). It works on android 7

No permission to write to /storage/emulated/0/download: Neither user 10205 nor current process has android.permission.WRITE_EXTERNAL_STORAGE.

Answer 1

You only need internet permission.

<uses-permission android:name="android.permission.INTERNET" />

and

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

if you want to store and read this downloaded file.

Answer 2

You are getting this error because your app is running in Android 6.0(API level 23). From API level >= 23 you will need to check for the permission in run time. Your code is just fine for below level 23. So please check first if your user has given the permission to use the storage:

if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE) == PackageManager.PERMISSION_GRANTED) {
    Log.e("Permission error","You have permission");
    return true;
}

If not then prompt the request:

ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_CODE);

Total things looks like this:

public  boolean haveStoragePermission() {
    if (Build.VERSION.SDK_INT >= 23) {
        if (checkSelfPermission(android.Manifest.permission.WRITE_EXTERNAL_STORAGE)
                == PackageManager.PERMISSION_GRANTED) {
            Log.e("Permission error","You have permission");
            return true;
        } else {

            Log.e("Permission error","You have asked for permission");
            ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, 1);
            return false;
        }
    }
    else { //you dont need to worry about these stuff below api level 23
        Log.e("Permission error","You already have the permission");
        return true;
    }
}

And receive the result by callback:

    @Override
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
        if(grantResults[0]== PackageManager.PERMISSION_GRANTED){
            //you have the permission now.
            DownloadManager.Request request = new DownloadManager.Request(Uri.parse(myurl));
            request.setTitle("Vertretungsplan");
            request.setDescription("wird heruntergeladen");
            request.allowScanningByMediaScanner();
            request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
            String filename = URLUtil.guessFileName(myurl, null, MimeTypeMap.getFileExtensionFromUrl(myurl));
            request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, filename);
            DownloadManager manager = (DownloadManager) c.getSystemService(Context.DOWNLOAD_SERVICE);
            manager.enqueue(request);
        }
    }

Answer 3

The internet permission is required:

<uses-permission android:name="android.permission.INTERNET" />

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You can use getExternalFilesDir if you want to save file without any storage permission. As stated in the documentation:

getExternalFilesDir

Added in API level 8

File getExternalFilesDir (String type)

Returns the absolute path to the directory on the primary shared/external storage device where the application can place persistent files it owns. These files are internal to the applications, and not typically visible to the user as media.

This is like getFilesDir() in that these files will be deleted when the application is uninstalled, however there are some important differences: Shared storage may not always be available, since removable media can be ejected by the user. Media state can be checked using getExternalStorageState(File). There is no security enforced with these files. For example, any application holding WRITE_EXTERNAL_STORAGE can write to these files.

If a shared storage device is emulated (as determined by isExternalStorageEmulated(File)), it's contents are backed by a private user data partition, which means there is little benefit to storing data here instead of the private directories returned by getFilesDir(), etc.

Starting in KITKAT, no permissions are required to read or write to the returned path; it's always accessible to the calling app. This only applies to paths generated for package name of the calling application.

To access paths belonging to other packages, WRITE_EXTERNAL_STORAGE and/or READ_EXTERNAL_STORAGE are required. On devices with multiple users (as described by UserManager), each user has their own isolated shared storage. Applications only have access to the shared storage for the user they're running as.

The returned path may change over time if different shared storage media is inserted, so only relative paths should be persisted.

https://developer.android.com/reference/android/content/Context#getExternalFilesDir(java.lang.String)

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This link may be useful:

Save files on device storage