How to get external usb mass storage path in Android?

Question

I need to import / export some data from / to a usb stick. Is there a way to get the path of the mounted usb devices?

My code looks something like this:

UsbManager manager = (UsbManager) getSystemService(Context.USB_SERVICE);
HashMap<String, UsbDevice> deviceList = manager.getDeviceList();
Iterator<UsbDevice> deviceIterator = deviceList.values().iterator();

while(deviceIterator.hasNext()){

    UsbDevice device = deviceIterator.next();
    UsbInterface deviceInterface = device.getInterface(0);

    if(deviceInterface != null && deviceInterface.getInterfaceClass() == UsbConstants.USB_CLASS_MASS_STORAGE){
        // check if path "mnt/usb_storage/*" exist
    }
}

I can search if the path "mnt/usb_storage/*" exists when the device is a mass storage. This works fine if only one usb mass storage is attached or the app is in foreground when a second usb mass storaged is attached. If you wonder, yes there are Android devices with multiple usb ports.

Is there no way to get the path when I have the UsbManager/UsbDevice/UsbInterface? Is the path on all devices like "mnt/usb_storage/*"?

Update 1:

Target Android Version 5.1 Requirement: "Filechooser" has to be integrated inside the app, filter for folders, file names und file types have to be applied.

Update 2:

As suggested by @greenapps I gave "ACTION_OPEN_DOCUMENT_TREE" a try:

Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
intent.putExtra("android.content.extra.SHOW_ADVANCED", true);
intent.putExtra("android.content.extra.FANCY", true);
intent.putExtra("android.content.extra.SHOW_FILESIZE", true);
startActivityForResult(intent, OPEN_DOCUMENT_TREE_REQUEST_CODE);

This does not show the usb stick neither was I able to filter the files and folders.

Same device: es-datei explorer is able to display the usb device.

My requirements are to display a custom file chooser where the user can select files from a customer specific cloud, internal storage or usb devices similar to the es datei explorer.

My solution with searching if the path: "mnt/usb_storage/*" exists works as required I am just wondering if there is a better way.

Answer 1

There mostly is no path on modern Android systems. Nowadays you will try to get a document tree scheme.

There are several options.

You could have a look at the second or third item returned by getExternalFilesDirs(). (Will give a path. But writing not possible.)

For Android 6+ use Intent.ACTION_OPEN_DOCUMENT_TREE to let the user choose the drive. This will give you a content sheme. No file path.

For Android 7+ have a look at Storage Volumes.

Answer 2

So I have searched quite a number of SO questions to get the path of a USB devices. I have not quite found an answer yet, but since this is top of the Google search and a fairly recent question, I will post what I have found.

Attempt (fleshed out)

So initially I tried (with my own implementation) as the question contains:

public static String getUSBProblematic(Context context){
    UsbManager usbManager = (UsbManager) context.getSystemService(Context.USB_SERVICE);
    if (usbManager == null) {
        Log.e(TAG, "Unable to get USB_SERVICE");
        return "";
    }
    UsbAccessory[] accessoryList = usbManager.getAccessoryList();
    if (accessoryList != null) {
        for (UsbAccessory usbAccessory : accessoryList) {
            // here we check the vendor
            Log.d(TAG, "getUSBProblematic: " + usbAccessory.toString());
        }
    }

    HashMap<String, UsbDevice> deviceList = usbManager.getDeviceList();
    if(deviceList != null) {
        List<UsbDevice> usbDeviceList = new ArrayList<>(deviceList.values());

        for (Iterator<UsbDevice> iterator = usbDeviceList.iterator(); iterator.hasNext();) {
            UsbDevice next = iterator.next();

            boolean isMassStorage = false;
            for (int i = 0; i < next.getInterfaceCount(); i++) {
                // Check USB interface type is mass storage
                UsbInterface usbInterface = next.getInterface(i);
                if(usbInterface.getInterfaceClass() == UsbConstants.USB_CLASS_MASS_STORAGE && usbInterface.getEndpointCount() == 2) {

                    // Check endpoints support bulk transfer
                    for (int j = 0; j < usbInterface.getEndpointCount(); j++) {
                        UsbEndpoint endpoint = usbInterface.getEndpoint(j);
                        if(endpoint != null) {
                            if(endpoint.getType() == UsbConstants.USB_ENDPOINT_XFER_BULK){

                                // Valid mass storage
                                isMassStorage = true;
                            }
                        }
                    }
                }
            }

            if(!isMassStorage) {
                iterator.remove();
            }
        }

        for (UsbDevice usbDevice : usbDeviceList) {
            Log.d(TAG, "getUSBProblematic: Device Name" + usbDevice.getDeviceName());
            Log.d(TAG, "getUSBProblematic: Device Desc" + usbDevice.toString());
        }
    }
    return "";
}

So the best I can get out of this is something like /dev/bus/usb/003, but nothing more than that.

So looking over my mounts file in /proc/mounts (found on the device, see Device File Explorer in Android Studio, I saw that USB specific storage devices are mounted at /mnt/media_rw/. But browsing to /storage, I saw the USB devices I expected or was looking for.

I am not sure if this is a good strategy or device specific (I use a Huawei Mate 10 Pro), but I am using

Possible Solution

public static String getUSB(){
    File storageDirectory = new File("/storage");
    if(!storageDirectory.exists()) {
        Log.e(TAG, "getUSB: '/storage' does not exist on this device");
        return "";
    }

    File[] files = storageDirectory.listFiles();
    if(files == null) {
        Log.e(TAG, "getUSB: Null when requesting directories inside '/storage'");
        return "";
    }

    List<String> possibleUSBStorageMounts = new ArrayList<>();
    for (File file : files) {
        String path = file.getPath();
        if (path.contains("emulated") ||
                path.contains("sdcard") ||
                path.contains("self")) {
            Log.d(TAG, "getUSB: Found '" + path + "' - not USB");
        } else {
            possibleUSBStorageMounts.add(path);
        }
    }

    if (possibleUSBStorageMounts.size() == 0) {
        Log.e(TAG, "getUSB: Did not find any possible USB mounts");
        return "";
    }
    if(possibleUSBStorageMounts.size() > 1) {
        Log.d(TAG, "getUSB: Found multiple possible USB mount points, choosing the first one");
    }

    return possibleUSBStorageMounts.get(0);
}

EDIT 1

This may also be useful (search for USB)