Access Files on a USB OTG device (SD Card reader) via MediaStore

Question

Can I access the Images on a USB OTG device (SD card reader) connected to my Android device with MediaStore?

I am able to access the files using the Storage Access Framework with this code. I'm trying to find specific images on the external USB device based on their last modified date and their file size. However the performance with SAF is terrible and I thought maybe MediaStores querying options might be more performant.

I tried to use MediaStore (MediaStore.Images.Media.EXTERNAL_CONTENT_URI) but it only seems to find files on the Android device.

I'm building for Android 12+

fun startIntent() {
    val storageManager = context.getSystemService(Context.STORAGE_SERVICE) as StorageManager
    storageManager.storageVolumes.map {
        if(it.isRemovable) {
            val intent = it.createOpenDocumentTreeIntent()
            currentActivity?.startActivityForResult(intent, USB_STORAGE_ACCESS_CODE)
        }
    }
}


override fun onActivityResult(activity: Activity, requestCode: Int, resultCode: Int, data: Intent?) {
    scope.launch {
        val treeUri = data?.data
        treeUri?.let { uri ->
            val documentFile = DocumentFile.fromTreeUri(activity, uri)
            val files = documentFile.listFiles()
            files.forEach { file ->
                this.filesToMatch?.forEach { fileToMatch ->
                    if (
                        file.length() == fileToMatch.length() &&
                        file.lastModified() == fileToMatch.lastModified()
                        ) {
                            // perform some operation
                    }
                }
            }
        }
    }
}

Answer 1

the performance with SAF is terrible val files = documentFile.listFiles()

Yes if you use DocumentFile its about twenty times as slow as the classic File class.

Better use DocumentsContract as it has about the same speed.