Enable listing the contents of a SAF subfolder

Author: Daniel Dunn

android/src/main/kotlin/io/lakscastro/sharedstorage/storageaccessframework/lib/DocumentCommon.kt

@@ -43,6 +43,8 @@ fun documentFromSingleUri(context: Context, uri: Uri): DocumentFile? {
   return DocumentFile.fromSingleUri(context, documentUri)
 }
 
+
+
 /**
  * Generate the `DocumentFile` reference from string `uri`
  */
@@ -161,10 +163,24 @@ fun traverseDirectoryEntries(
   rootOnly: Boolean,
   block: (data: Map<String, Any>, isLast: Boolean) -> Unit
 ): Boolean {
-  val childrenUri = DocumentsContract.buildChildDocumentsUriUsingTree(
-    rootUri,
-    DocumentsContract.getTreeDocumentId(rootUri)
-  )
+
+
+  var childrenUritmp: Uri?;
+
+
+  //https://stackoverflow.com/questions/41096332/issues-traversing-through-directory-hierarchy-with-android-storage-access-framew
+  //Credit to user: Foobnix
+  //If we were to always use getTreeDocumentId, it would apparently always only list the top level folder even if you request a subfolder
+
+  try {
+      //for childs and sub child dirs
+       childrenUritmp = DocumentsContract.buildChildDocumentsUriUsingTree(rootUri, DocumentsContract.getDocumentId(rootUri));
+  } catch (e:Exception) {
+      // for parent dir
+       childrenUritmp = DocumentsContract.buildChildDocumentsUriUsingTree(rootUri, DocumentsContract.getTreeDocumentId(rootUri));
+  }
+
+  val childrenUri = childrenUritmp as Uri;
 
   /// Keep track of our directory hierarchy
   val dirNodes = mutableListOf<Pair<Uri, Uri>>(Pair(rootUri, childrenUri))