opening an external "file explorer" app: how to get absolute path from a uri pointing to a folder

In my app, the user can choose where the created files (text files) are created. This part is working fine. But now, I want to open an external "file explorer" app, pointing directly to the chosen folder. The "file explorer " apps I know accept an absolute path as input (like /storage/emulated/0/Documents/test_folder)

When the user chooses a folder (with Intent.ACTION_OPEN_DOCUMENT_TREE), I get a content uri (like content://com.android.externalstorage.documents/tree/home%3Atest_folder)

Another example with an external sd card:

• uri: content://com.android.externalstorage.documents/tree/3877-DB74%3ADocuments%2Ftest_folder
• expected path: /storage/3877-DB74/Documents/test_folder

The uri points to a folder, not a file, so I can't use something like openInputStream

I have tried :

File f = new File(uri.getPath());
String path = f.getAbsolutePath();

but it gives: /tree/home:test_folder or /tree/3877-DB74:Documents/test_folder if on sd card

How can I get the real absolute path?

The code I use to call a file explorer:

Intent intent = new Intent(Intent.ACTION_VIEW);
String path = getExternalFilesDir(null).getAbsolutePath();
intent.setDataAndType(Uri.parse(path), "resource/folder");
if (intent.resolveActivityInfo(getPackageManager(), 0) != null)
{
    startActivity(intent);
}

I finally wrote my own method to get the absolute path for a folder from a Uri. It is surely not fully generic, but it meets my need.

if it can help someone, here is my code:

Note: VOLUME_MAP is a map containing all mounted external volumes

    /**************************************************************************/
    public static String getRealPathFromContentUri(final Uri uri)
    {
        if (!isExternalStorageDocument(uri))
        {
            return null;
        }

        List<String> segs = uri.getPathSegments();
        if (!"tree".equalsIgnoreCase(segs.get(0)))
        {
            return null;
        }

        String path = uri.getLastPathSegment();
        final String[] split = path.split(":");
        final String volumeId = split[0];
        String userPath = "";
        if (split.length > 1)
        {
            userPath = "/" + split[1];
        }
        if ("primary".equalsIgnoreCase(volumeId))
        {
            return Environment.getExternalStorageDirectory().getAbsolutePath() + userPath;
        }

        if ("home".equalsIgnoreCase(volumeId))
        {
            return Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS).getAbsolutePath() + userPath;
        }

        // look for real volumeId
        final String volumeName = VOLUME_MAP.get(volumeId);
        if (volumeName == null)
        {
            return null;
        }
        path = "/storage";
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.R)
        {
            path = Environment.getStorageDirectory().getAbsolutePath();
        }
        return path  + "/" + volumeId + userPath;
    }

Here is how to get VOLUME_MAP:

private static Map<String, String> initVolumeMap()
{
    final Map<String, String> volumeMap = new HashMap<>();
    volumeMap.put("primary", null); 
    volumeMap.put("home", "Documents"); 

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N && PadocApp.getInstance() != null)
    {
        final Context context = MyApp.getInstance().getApplicationContext();
        final StorageManager storageManager = ContextCompat.getSystemService(context, StorageManager.class);
        assert storageManager != null;
        final List<StorageVolume> storageVolumes = storageManager.getStorageVolumes();
        for (StorageVolume sv : storageVolumes)
        {
            volumeMap.put(sv.getUuid(), sv.getDescription(context));
        }
    }
    else
    {
        //at least we create a default entry for the primary drive
        volumeMap.put(null, "internal shared storage");
    }
    return volumeMap;
}

Thanks to all contributors on this topic.