Develop Reference

Uri Path getting a file list

Android 11 / Api 30
Lets say I have a path to a user selected path (URI) on an Android devices, how would I go about walking through that directory and not the sub directories that might be deeper within it, for files with the extension .pref, so that those files could be loaded later.
I've already done code for walking a path with in my own applications directory, but cannot find how I would do that from a user selected path in shared/external storage.

Lets say I have a path to a user selected path (URI)
A Uri is not a filesystem path. For example, https://stackoverflow.com/questions/68510202/uri-path-getting-a-file-list is a Uri.
how would I go about walking through that directory
I am going to assume that you obtained the Uri via ACTION_OPEN_DOCUMENT_TREE / ActivityResultContracts.OpenDocumentTree.
how would I go about walking through that directory and not the sub directories that might be deeper within it, for files with the extension .pref, so that those files could be loaded later
There is no requirement for content in a documents provider to have file extensions, so your approach will not work for all cases. But, you can wrap the Uri in a DocumentFile using fromTreeUri(), then call listFiles() on the DocumentFile:
val docRoot: DocumentFile? = DocumentFile.fromTreeUri(this, uri)
val docPrefs: List<DocumentFile> = docRoot?.listFiles().orEmpty()
.filterNot { it.isDirectory }
.filter { it.name.orEmpty().endsWith(".pref") }
val docs: List<Uri> = docPrefs.map { it.uri }
Here, docPrefs is the list of non-directory children of your root that happen to have a display name that ends in .pref.
so that those files could be loaded later
That will only work if you call takePersistableUriPermission() on the Uri that you got from ACTION_OPEN_DOCUMENT_TREE.

How do I use the root Uri of the SD card to find a file inside a folder

I need to rename files that are in subfolders in the SD card so I got the root Uri of the Sd card with the permission Intent.ACTION_OPEN_Document_TREE. Whenever I use documentFile.findFile() it only finds files that are in the root path(files that are not in subfolders).How do I find other files that are not in the root path.

String exampleAbsolutePath="/storage/sdCardName/Folder1/Folder2/myFile.mp4";
String []splitPathArray=exampleAbsolutePath.split("/");
DocumentFile documentFile= DocumentFile.fromTreeUri(myContext,sdCardRootUri);//sdCardRootUri is the **Root** Uri got from Intent.ACTION_OPEN_Document_TREE
for(int pos=3;pos<splitPath.length;++pos){//pos starts from 3 because the sdCardRootUri is pointing to the sdCardName and we need to start searching from Folder1
documentFile=documentFile.findFile(splitPath[pos]);}//findFile() can take both files and folders,it takes the file or folder display name(i.e the name of the file(with the extension e.g file.mp4,photo.png in the **exampleAbsolutePath** the file name is myFile.mp4) or the folderName e.g Music Folder,Photo Album,Videos,Documents in the **exampleAbsolutPath** the folder display names we iterate through are Folder1 and Folder2)
if(documentFile!=null){
documentFile.renameTo(newDisplayName);}//rename old file display Name to the new file dispaly name
You might want to do this file rename in a Thread as it can be a little bit slow.

Creating a writeable DocumentFile from URI

I'm trying to adapt a File-based document system to something using DocumentFile in order to allow external storage read/write access on API >= 29.
I get the user to select the SD card root using Intent.ACTION_OPEN_DOCUMENT_TREE, and I get back a Uri as expected, which I can then handle using:
getContentResolver().takePersistableUriPermission(resultData.getData(),
Intent.FLAG_GRANT_READ_URI_PERMISSION
| Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
I can browse successfully through the external storage contents up to the selected root. All good.
But what I need to be able to do is write an arbitrary file in the chosen (sub)folder, and that's where I'm running into problems.
DocumentFile file = DocumentFile.fromSingleUri(mContext, Uri.parse(toPath));
Uri uri = file.getUri();
FileOutputStream output = mContext.getContentResolver().openOutputStream(uri);
Except on the openOutputStream() call I get:
java.io.FileNotFoundException: Failed to open for writing: java.io.FileNotFoundException: open failed: EISDIR (Is a directory)
That's slightly confusing to me, but the "file not found" part suggests I might need to create the blank output file first, so I try that, like:
DocumentFile file = DocumentFile.fromSingleUri(mContext, Uri.parse(toPath));
Uri uri = file.getUri();
if (file == null) {
return false;
}
if (file.exists()) {
file.delete();
}
DocumentFile.fromTreeUri(mContext, Uri.parse(getParentPath(toPath))).createFile("", uri.getLastPathSegment());
FileOutputStream output = mContext.getContentResolver().openOutputStream(uri);
I get a java.io.IOException:
java.lang.IllegalStateException: Failed to touch /mnt/media_rw/0B07-1910/Testing.tmp: java.io.IOException: Read-only file system
at android.os.Parcel.createException(Parcel.java:2079)
at android.os.Parcel.readException(Parcel.java:2039)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:188)
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:140)
at android.content.ContentProviderProxy.call(ContentProviderNative.java:658)
at android.content.ContentResolver.call(ContentResolver.java:2042)
at android.provider.DocumentsContract.createDocument(DocumentsContract.java:1327)
at androidx.documentfile.provider.TreeDocumentFile.createFile(TreeDocumentFile.java:53)
at androidx.documentfile.provider.TreeDocumentFile.createFile(TreeDocumentFile.java:45)
Which doesn't make sense to me, since the tree should be writeable.
For what it's worth, the Uri I get back from Intent.ACTION_OPEN_DOCUMENT_TREE looks like this:
content://com.android.externalstorage.documents/tree/0B07-1910%3A
Interestingly, when I use that Uri to create a DocumentFile object to browse, using documentFile = DocumentFile.fromTreeUri(context, uri), then documentFile.getURI().toString() looks like:
content://com.android.externalstorage.documents/tree/0B07-1910%3A/document/0B07-1910%3A
i.e., it's had something appended to the end of it.
Then, I descend into what should be a writeable folder (like "Download"), and try creating a writeable file as described above. The "Download" folder gets the Uri:
content://com.android.externalstorage.documents/tree/0B07-1910%3A/document/0B07-1910%3ADownload
and the Uri I'm using for toPath, above, is then:
content://com.android.externalstorage.documents/tree/0B07-1910%3A/document/0B07-1910%3ADownload/Testing.tmp
which leads to the problems described previously trying to create it.
I haven't actually found any decent information about writing an arbitrary file under Storage Access Framework restrictions.
What am I doing wrong? Thanks. :)

Uri uri = uri obtained from ACTION_OPEN_DOCUMENT_TREE
String folderName = "questions.59189631";
DocumentFile documentDir = DocumentFile.fromTreeUri(context, uri);
DocumentFile folder = documentDir.createDirectory(folderName);
return folder.getUri();
Use createFile() for a writable file.

How to delete a file in /download (ora any other folder) in the android external storage with DocumentProvider through Kotlin?

I'm [still] new on android development and about Java and about Kotlin (also an explanation in Java could be ok, however, I'm studying it also, Kotlin is prefered) and I'm struggling for deleting a simple downloaded file into the ExternalStorage.
Of course I enabled permission for read & write, and, even if this code returns a "True", I still can see the untouched file into my Download folder
here the code:
___UPDATE
// uri of my file in external storage ~/Download dir
var uri = Uri.parse (Environment.getExternalStorageDirectory().getPath() + "/Download/$myFilename$myExtensionVar")
// file object pointing at uri of file in external storage
val downloadedFile = File(uri.toString())
var deletedBool:Boolean = downloadedFile.delete()
println("myTag - deleted Boolean: $deletedBool")
if (deletedBool){
println("myTag - uri of file-to-be-deleted: $uri")
var secondStepToDelete:Int = context.getContentResolver().delete(uri, null, null)
println("myTag - second Step for deletion: $secondStepToDelete")
}
The file i am trying to rid of is a multimedia file (.mp3) and I added the second block of code (the one inside the IF statement) since I found that should work, having to do with the "DocumentProvider" (I'm new and I still don't know how to proper call its methods..) but, of course, It doesn't work at all.
I think I do need the ID (long type i guess) for the file stored into the external storage, however I haven't found yet how to get it
Thanks in advance for the help!

To build a File object, use the File constructor. To build a File object for a location off of a certain root directory, use the two-parameter File(File, String) constructor:
val downloadedFile = File(Environment.getExternalStorageDirectory(), "Download/$myFilename$myExtensionVar")
Unless you are getting a Uri from DownloadManager or something, there is no Uri that you need to delete().
I have more written here on external storage and how to work with it.

In Kotlin
file.deleteRecursively()

Get File Uri from Document Id in Storage Access Framework

I am using directory selection as described in this Google Sample. It does provide file name and mime type of the children of the selected directory. I can get Document ID of the file too, if I use COLUMN_DOCUMENT_ID on the Cursor Query.
I am interested in the file URI of the children instead. When I use ACTION_OPEN_DOCUMENT instead of ACTION_OPEN_DOCUMENT_TREE, I get the child uri easily which is just obtained from adding a %2Fchildfile.extention (%2F is just a forward slash). So I tried to get child file uri using the following code -
uri = Uri.parse(docUri.toString()+"%2F"+fileName);
I got the file name, however when I run exists() method on it (By converting it into DocumentFile), it returns false. That means, either I don't have the permission of the file or it's not the correct way to get children uri.
Am I missing something here or is there any other way I can select a folder and get file uri of all of it's children easily.
PS: I am currently checking it in Marshamallow.

After reading the doc and trying out certain examples, I got the following way to get a single file Uri from a selected docUri/treeUri
uri = DocumentsContract.buildDocumentUriUsingTree(docUri,docId);
And then you can convert it anytime into a DocumentFile using following code -
DocumentFile file = null;
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.KITKAT) {
if (DocumentsContract.isDocumentUri(context, uri)) {
file = DocumentFile.fromSingleUri(context, uri);
} else {
file = DocumentFile.fromTreeUri(context, uri);
}
}
fromTreeUri() method is required for the selected Tree Directory, so that it can return true on file.exists() method call.
You need to remember that if the children contain any directory, then you can't call childDirectory.listFiles() on it. It'll give UnsupportedOperationException, because you don't have permission to access the child directory's file. Read more about this here.