SAF: App Inventor implementation of Storage Access Framework

vknow360 · September 17, 2021, 4:05pm

1.Introduction

Description: Basically AI2 wrapper of Storage Access Framework. Using this extension, you can get read and/or write access to a single document or tree document (and all of its children recursively).
Latest Version: 1.1
Released: 2021-09-16T18:30:00Z
Last Updated: 2021-11-01T18:30:00Z

2.Blocks

3.Documentation

Docs for: SAF

Events

DocumentCreated
Event invoked after creating document.Returns document's uri if operation was successful else returns error message

Params

uriString | text

ErrorOccurred
Event indicating error/exception has occurred and returns origin method and error message.

Params

methodName | text
errorMessage | text

GotCopyResult
Event invoked after getting copy document result.Response will be target document's uri if operation was successful else returns error message

Params

successful | boolean
response | text

GotFilesList
Event invoked after getting files list

Params

filesList | list

GotMoveResult
Event invoked after getting move document result.Response will be target document's uri if operation was successful else returns error message

Params

successful | boolean
response | text

GotReadResult
Event invoked after reading from document.Returns content if operation was successful else returns error message

Params

result | any

GotUri
Event invoked when user selects a document or tree from SAF file picker

Params

uri | any
uriString | text

GotWriteResult
Event invoked after writing to document.Returns document's uri if operation was successful else returns error message

Params

response | text

Methods

BuildChildDocumentsUriUsingTree
Builds child documents id using tree (documents which is child of parent document) uri and its parent document id

Params

treeUri | text

parentDocumentId | text

Return type : text

BuildDocumentUriUsingTree
Builds document uri using tree uri and document id

Params

treeUri | text

documentId | text

Return type : text

CopyDocument
Tries to copy document from source uri to target dir

Params

sourceUri | text

targetParentUri | text

CreateDocument
Creates a new and empty document.If document already exists then an incremental value will be suffixed.

Params

parentDocumentUri | text

fileName | text

mimeType | text

CreateFlags
Combines two flags and returns resulting flag

Params

f1 | number

f2 | number

Return type : number

DeleteDocument
Tries to delete document from given uri and returns result

Params

uriString | text

Return type : boolean

GetDisplayName
Returns display name of given document uri

Params

documentUri | text

Return type : text

GetDocumentId
Returns document id of an uri (should only be grand child)

Params

uriString | text

Return type : text

GetLastModifiedTime
Returns last modified time (epoch) of given document uri

Params

documentUri | text

Return type : text

GetMimeType
Returns mime type of given document uri

Params

documentUri | text

Return type : text

GetSize
Returns size (in bytes) of given document uri

Params

documentUri | text

Return type : text

GetTreeDocumentId
Returns document id of tree uri (should be either tree uri itself or a direct child uri)

Params

uriString | text

Return type : text

IsChildDocumentUri
Returns whether second uri is child of first uri

Params

parentUri | text

childUri | text

Return type : boolean

IsCopySupported
Returns whether document can be copied or not

Params

documentUri | text

Return type : boolean

IsDeleteSupported
Returns whether document is deletable or not

Params

documentUri | text

Return type : boolean

IsDocumentUri
Returns whether given uri is a document uri

Params

uriString | text

Return type : boolean

IsMoveSupported
Returns whether document is movable or not

Params

documentUri | text

Return type : boolean

IsReadGranted
Returns whether read is available for given uri

Params

uri | text

Return type : boolean

IsRenameSupported
Returns whether document is deletable or not

Params

documentUri | text

Return type : boolean

IsTreeUri
Returns whether given uri is a tree uri

Params

uriString | text

Return type : boolean

IsWriteGranted
Returns whether write is available for given uri

Params

uri | text

Return type : boolean

ListFiles
Tries to list files from given dir

Params

dirUri | text

dirDocumentId | text

MoveDocument
Tries to move document from source uri to target dir

Params

sourceUri | text

sourceParentUri | text

targetParentUri | text

OpenDocumentTree
Prompts user to select a document tree

Params

title | text

initialDir | text

OpenSingleDocument
Prompts user to select a single file

Params

title | text

type | text

extraMimeTypes | list

ReadAsByteArray
Reads content of document as byte array

Params

uriString | text

ReadFromFile
Reads from given document as text

Params

uriString | text

ReleasePermission
Relinquish a persisted URI permission grant

Params

uri | text

flags | number

RenameDocument
Tries to rename a document and returns updated uri

Params

documentUri | text

displayName | text

Return type : text

StringFromUriObject
Convert uri to string

Params

uri | any

Return type : text

StringToUriObject
Converts string to uri

Params

uriString | text

Return type : any

TakePersistableUriPermission
Take a persistable URI permission grant that has been offered. Once taken, the permission grant will be remembered across device reboots.

Params

uri | any

flags | number

WriteAsByteArray
Writes byte array to given document

Params

uriString | text

byteArray | any

WriteToFile
Writes to given uri

Params

uriString | text

content | text

Properties

DocumentDirMimeType
Returns mime type of document dir

Property Type : read-only
Accepts : text

FlagGrantReadPermission
Flag to get write permission

Property Type : read-only
Accepts : number

FlagGrantWritePermission
Flag to get read permission

Property Type : read-only
Accepts : number

4.Usages

will be updated frequently

1.Open document tree

2.Get access (not necessary for one-time usage)

3.Build child document uri

if document is direct child

if document is grandchild

4.Read file/Set picture

5.Download

Aix: com.sunny.saf.aix (30.6 KB)

6.Open Source

7.Liked my work/Want to donate

Thank you

8. ChangeLog

ChangeLog Version 1.1

New Blocks

Changes

Removed category param from OpenSingleDocument method
GotCopyResult and GotMoveResult now return resulting/target document's uri

Bug Fixes

Fixed issue in write methods
Fixed null pointer exception when SAF picker was cancelled by user

Hope it helps!

Anke · September 17, 2021, 4:14pm

What an amazing extension ! Great job!
I’ve only done a few tests and it seems to be working so far.

And it's a shame that your extensions need approval in AI2.
We should change that as soon as possible!

ABG · September 17, 2021, 4:16pm

This looks important.

But I am not sure exactly what constitutes a document here.

Surely not a Microsoft .doc file?
A .html file with links to other .html files nearby?
an in-memory runtime structure ?

vknow360 · September 17, 2021, 4:21pm

We can consider document as strictive version of normal files, which are accessible only via URIs.
File class is part of java.io while Document/ Document File is implementation of Google for File System to give user more control over his device , files and privacy.

ABG · September 17, 2021, 4:25pm

That java.io link sent me into some kind of UAE discussion group.
I was expecting a documentation page for java, maybe under oracle.com?

KUMARASWAMY_B.G · September 17, 2021, 4:31pm

I guess he did not mean to link any resource but just referring the java.io system.

Salman_Dev · September 17, 2021, 4:44pm

For Real

That is the Best Extension, Good Job

Know_About_IT · September 18, 2021, 6:25am

Epic work @vknow360

TIMAI2 · September 18, 2021, 11:16am

As @ABG says, this looks important, but I am guessing that most developers (which includes me) are not in the lucky 10,000 on this one, and therefore haven't got a clue as to what this is about our how they might use it in their apps. The example blocks give an inkling, but don't really help. Could a better description be provided, in layman's terms, of What this extension does, Why/When/Where one might use it, and How it works in more detail?

I am certain the work adds value to the AI2 development experience, especially in these times of Google privacy concerns and file location lockdown, but there is little point saying "great extension" in a post, if I have no understanding of what it does.

vknow360 · September 18, 2021, 11:52am

Yes, SAF is quite complicated to understand because Google had no time to explain why they decided to strict app's access to file system. Most developers felt homely by using legacy "File" approach, but launching of Android 10 started causing troubles for them and SAF is the solution to most of their problems.
Using this, you can-

access phone storage*
access SD card*
read from/write to files created by other apps
help user in protecting his/her data and restrict Storage consumed by apps
get access to files and folders which are important to your app.
In this way, you needn't ask for MANAGE_EXTERNAL_STORAGE permission.
work with non-media files too, such as creating a CSV file of user's data or accessing a PDF file

*: Android/data and Android/obb folders are exception

One major advantage I would like to emphasize is usage of URIs instead of paths.

vknow360 · September 18, 2021, 2:03pm

Example 2

Open document picker and create document

image1036×450 46.8 KB

(Since you now know how to take persistable permission, so I'll skip that part)
Read and write to document

image761×463 29.9 KB
List files

image973×435 44.6 KB

SteveJG · September 18, 2021, 2:13pm

Developers might also find these links about SAF useful in addition to your nice explanation.

TIMAI2 · September 18, 2021, 2:16pm

Thanks @vknow360 for your explanations, making more sense now as to what one can do with your extension.

TIMAI2 · September 18, 2021, 3:08pm

Well I have fallen at the first hurdle....

Following your first image, when I click the button I am taken to the device's default file manager (or what looks like it), I went to the root folder, the file manager asked me to give permission to this area (to MIT Companion App), then returns me to the project with this error:

vknow360 · September 18, 2021, 3:13pm

I forget to mention that direct child's id should be obtained using GetTreeDocumentId method.

TIMAI2 · September 18, 2021, 3:15pm

Sorry, I used the wrong block

TIMAI2 · September 18, 2021, 3:38pm

OK that all works.

Is there no way then, in order to get started, other than the user going into their file manager and granting a permission, to get the root or other folder (tree)? (Open Document Tree)

Perhaps a uri for the ASD ?

I can see how one can traverse through a file list to find sub (folders) trees, and then list files again and so on. An image component accepts a content uri to display an image. Is this going to be the same for other components needing a file?

vknow360 · September 18, 2021, 3:50pm

No, user must grant access through Documents Picker.

I am not sure about this.
Image component works fine.
Same should be correct for audio and video player.

TIMAI2 · September 18, 2021, 4:18pm

Understood

Anke · September 18, 2021, 4:25pm

SAF is only needed for → non-media files. Media files (jpg, png, mp3, m4a, mp4,...) can be accessed from all paths (outside of the ASD or privateDir) with READ permission.