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.

Android SAF, cannot copy file, FLAG_SUPPORTS_COPY not set

I'm trying to copy a document with the SAF framework in Android by using DocumentsContract.copyDocument(ContentResolver, Uri, Uri) however this doesn't work, android returns error "Failed to copy document".
By narrowing the issue down, the FLAG_SUPPORTS_COPY is off on that document (according to DocumentsContract.Document#COLUMN_FLAGS)
(COLUMN_FLAGS value is 326 in decimal). So this explains the error.
However moving the document is allowed (flag FLAG_SUPPORTS_MOVE is on) and file is really moved when calling DocumentsContract.moveDocument(ContentResolver, Uri, Uri, Uri)
Access to the document tree (both the root of the drive, and DCIM folder) have been granted through Intent.ACTION_OPEN_DOCUMENT_TREE
Why is the FLAG_SUPPORTS_COPY set to false for the Document ? Am I missing something ?
Note: I believe I fullfill the requirements from this post https://stackoverflow.com/a/58147682/15401262
Thank you
Code (java)
// docFilesToProcess if of type "DocumentFile[]" and contains "regular files, like images" (not directories).
// Create destination dir
Uri destUri = DocumentsContract.createDocument(this.getContentResolver(), docFilesToProcess[i].getParentFile().getUri(), DocumentsContract.Document.MIME_TYPE_DIR, "destDir");
Log.i("M", "destUri: "+ destUri.toString());
// Create document
Uri docToMove = DocumentsContract.createDocument(this.getContentResolver(), docFilesToProcess[i].getParentFile().getUri(), "text/plain", "text");
Log.i("M", "docToMove: "+ docToMove.toString());
// copy document
DocumentsContract.copyDocument(this.getContentResolver(), docToMove, destUri);
Output
I/M: destUri: content://com.android.externalstorage.documents/tree/primary%3ADCIM/document/primary%3ADCIM%2FdestDir
I/M: docToMove: content://com.android.externalstorage.documents/tree/primary%3ADCIM/document/primary%3ADCIM%2Ftext.txt
W/DocumentsContract: Failed to copy document
java.lang.UnsupportedOperationException: Copy not supported
at android.database.DatabaseUtils.readExceptionFromParcel(DatabaseUtils.java:172)
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.copyDocument(DocumentsContract.java:1442)
at com.example.exifthumbnailadder.MainActivity.addThumbs(MainActivity.java:1036)
at java.lang.reflect.Method.invoke(Native Method)
Persistant permission request
Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
intent.addFlags(
Intent.FLAG_GRANT_READ_URI_PERMISSION
| Intent.FLAG_GRANT_WRITE_URI_PERMISSION
| Intent.FLAG_GRANT_PERSISTABLE_URI_PERMISSION
| Intent.FLAG_GRANT_PREFIX_URI_PERMISSION);

In general, you cannot ever rely on any SAF provider to implement any optional feature. You should check whether the feature is supported, and you should have a viable fallback plan for when it is not.
ContentResolver cr = getContentResolver();
if((flags & FLAG_SUPPORTS_MOVE) == FLAG_SUPPORTS_MOVE)
Uri newDoc = DocumentsContract.copyDocument(cr, docToCopy, destDir);
else {
Uri newDoc = DocumentsContract.createDocument(cr, destDir, mimeType, name);
manuallyCopyBytes(docToCopy, newDoc);
}
It's important to give the provider a chance to do it, because something like Google Drive may be able to perform the copy separately on the device and on the server, instead of copying it on the device and then having to upload the whole thing to the server again.

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.

java.io.IOException: Cannot make changes to file

I am using JAudioTagger library for reading and writing tags for an audio file. I am able to read the tags but unable to write them.
I am retrieving audio file path like this :
private String getSongPath(long songId) {
String path = null;
ContentResolver contentResolver = getContentResolver();
Uri uri = MediaStore.Audio.Media.EXTERNAL_CONTENT_URI;
String[] projection = {MediaStore.Audio.Media.DATA};
String selection = MediaStore.Audio.Media._ID + " == ?";
String[] selectionArgs = {String.valueOf(songId)};
Cursor cursor = contentResolver.query(uri, projection, selection, selectionArgs, null);
if (cursor != null) {
int pathCol = cursor.getColumnIndexOrThrow(projection[0]);
cursor.moveToFirst();
path = cursor.getString(pathCol);
cursor.close();
}
return path;
}
Then to write tags using JAudioTagger :
File songFile = new File(path); // path looks like /storage/3932-3434/Music/xyz.mp3
AudioFile audiofile = = AudioFileIO.read(songFile);
Tag tag = = audiofile.getTag();
tag.setField(FieldKey.TITLE, title);
// some more setField calls for different feilds
audiofile.commit();
The commit() method is giving following Exception :
org.jaudiotagger.audio.exceptions.CannotWriteException:
java.io.IOException: Cannot make changes to file xyz.mp3 at
org.jaudiotagger.audio.mp3.MP3File.commit(MP3File.java:799) at
com.techapps.musicplayerplus.MainActivity$17.onClick(MainActivity.java:2125)
at
android.support.v7.app.AlertController$ButtonHandler.handleMessage(AlertController.java:157)
at android.os.Handler.dispatchMessage(Handler.java:102) at
android.os.Looper.loop(Looper.java:148) at
android.app.ActivityThread.main(ActivityThread.java:5417) 06-18
10:59:48.134 8802-8802/com.techapps.musicplayerplus W/System.err:
at java.lang.reflect.Method.invoke(Native Method) at
com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused
by: java.io.IOException: Cannot make changes to file Saibo.mp3 at
org.jaudiotagger.audio.mp3.MP3File.precheck(MP3File.java:824) at
org.jaudiotagger.audio.mp3.MP3File.save(MP3File.java:850) at
org.jaudiotagger.audio.mp3.MP3File.save(MP3File.java:783) at
org.jaudiotagger.audio.mp3.MP3File.commit(MP3File.java:795)
I am running this code on Android 6 while my app is targeted at SDK 22. I have also mentioned following permission in manifest.
android.permission.WRITE_EXTERNAL_STORAGE
Still I am unable to write to SD card. Please help me. Thanks in advance.

You have to use Storage Access Framework (SAF) to access SD Card from API 19 (Kitkat) onward.
First we need to ask user to provide a URI of the folder we want to access. If we want access to entire SD card, user needs to provide URI of SD card's root folder.
For example, when user hits Edit button, we have to first show hint dialog box, asking user to select required directory in SD Card which we want to access. You can display following image in hint dialog box to ask user to select root directory of SD Card :
When user dismisses hint dialog box, you need to trigger Storage Access Framework :
private void triggerStorageAccessFramework() {
Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT_TREE);
startActivityForResult(intent, REQUEST_CODE_STORAGE_ACCESS);
}
public final void onActivityResult(final int requestCode, final int resultCode, final Intent resultData) {
if (resultCode == Activity.RESULT_OK) {
if (requestCode == REQUEST_CODE_STORAGE_ACCESS) {
Uri treeUri = null;
// Get Uri from Storage Access Framework.
treeUri = resultData.getData();
pickedDir= DocumentFile.fromTreeUri(this, treeUri);
if (!isSDCardRootDirectoryUri(treeUri)) {
Toast.makeText(this, "Wrong directory selected. Please select SD Card root directory.", Toast.LENGTH_LONG).show();
createSDCardHintDialog().show();
return;
}
// Persist URI in shared preference so that you can use it later.
SharedPreferences sharedPreferences = getSharedPreferences(App.PREFERENCE_FILENAME, Context.MODE_PRIVATE);
SharedPreferences.Editor editor = sharedPreferences.edit();
editor.putString(App.SDCARD_URI_KEY, treeUri.toString());
editor.apply();
// Persist access permissions, so you dont have to ask again
final int takeFlags = resultData.getFlags() & (Intent.FLAG_GRANT_READ_URI_PERMISSION | Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
getContentResolver().takePersistableUriPermission(treeUri, Intent.FLAG_GRANT_WRITE_URI_PERMISSION);
}
}
private boolean isSDCardRootDirectoryUri(Uri treeUri) {
String uriString = treeUri.toString();
return uriString.endsWith("%3A");
}
Once you get Uri of user picked directory, you can perform write operation using SAF : (creadit : this answer )
public void writeFile(DocumentFile pickedDir) {
try {
DocumentFile file = pickedDir.createFile("image/jpeg", "try2.jpg");
OutputStream out = getContentResolver().openOutputStream(file.getUri());
try {
// write the image content
} finally {
out.close();
}
} catch (IOException e) {
throw new RuntimeException("Something went wrong : " + e.getMessage(), e);
}
}

It could be that you pointing to non existing file.
Check your path file by using Log.
Log.d("Activity", "path = " + path);

Android-M or API 23 introduced Runtime Permissions for reducing security flaws in android device.
To update your apps using Google Play services to handle Android 6.0 permissions, it’s good practice to manage the user’s expectations in setting permissions that the runtime may require. The following link will help you avoid potential issues.
https://developer.android.com/training/permissions/requesting.html

have you declared the permission
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/> ?

I saw that you already created an issue in the JAudioTagger GitHub repository which was advisable, but never got a universally working solution. My findings so far:
The answer mentioning SAF is correct, but it won't help you as SAF will provide a DocumentFile, not a File.
You might try to modify JAudioTagger to your needs, replacing File with DocumentFile, but the latter one has not all functions you will need.
Also InputStream and OutputStream will not help you, as JAudioTagger needs File and internally heavily uses RandomAccessFile which is not available either.
Google "forgot" to provide some getRandomAccessFileFromUri() which makes things even worse (Yes, there are hacks using Java reflection to work around this limitation...).
The "/proc/self/fd" method (How to handle SAF when I can only handle File or file-path?) will also not work immediately, as JAudioTagger needs copy and renaming functions that are not applicable to this kind of files. Particularly JAudioTagger will not find a suitable file name extension like ".m4a". Of course you could try to change JAudioTagger accordingly.
You might follow the advice to make a copy of the file to your personal storage, then apply JAudioTagger to it and finally copy it back to SD card, but:
If you want to use JAudioTagger to read from SD card, this will, as announced by Google, fail with Android 10. Starting with that version, you will not even have read access to the SD card via the File interface.
Further, the File interface gives you read access to SD cards with Android 9 and below, but not to other SAF devices, like USB OTG memory or SMB shares etc.
Of course you could also copy each file in order to read its metadata, but this will be awfully slow and is not suitable if you have more than a few files.
So my current advices are:
Try the "/proc/self/fd" method and modify JAudioTagger accordingly.
If the changes are too heavy, use the fd method for reading the tags and the copy method for writing.
BTW: I am currently modifying an older version of JAudioTagger for using both File and DocumentFile transparently, but the changes are tremendous, bear a high risk, need some help classes, and the work is unfinished, yet.
BTSW: The DocumentFile functions are painfully slow, compared to the File functions.