[shared_preferences] [windows,linux] Data can be corrupted due to lack of atomic file writes

[krll-kov]

 SharedPreferences _preferences = await SharedPreferences.getInstance();

This code simply fails with an error if config file is broken. Maybe it's good to clear preferences file if it contains an error. I do not know why the preferences file breaks but since i've published my app, there were some users, who reported this issue.

Platform where i faced this issue: Windows.

Flutter version: 2.2.3 from stable channel.

I have no idea why but file becomes something like this

[darshankawar]

@kirill-21
Please provide a complete minimal code sample.
Also can you elaborate on if config file is broken. with an example ?

[krll-kov]

@kirill-21
Please provide a complete minimal code sample.
Also can you elaborate on if config file is broken. with an example ?

Rename .txt -> .json (github does not allow to upload .json) (if you open it with notepad++, you'll see a lot of NUL NUL NUL NUL...)
shared_preferences.txt

add this to dependencies

dependencies:
  shared_preferences: ^2.0.7

place renamed shared preferences file to your's application folder (%appdata%/com.yourname/yourname [Example: C:\Users\user\AppData\Roaming\com.gskinner\flutter_folio\shared_preferences.json]) and add this into the main() function

SharedPreferences _preferences = await SharedPreferences.getInstance();

[darshankawar]

@kirill-21
Sorry where do I need to put the file again ?
I renamed it to shared_preferences.json.

[krll-kov]

@kirill-21
Sorry where do I need to put the file again ?
I renamed it to shared_preferences.json.

%appdata%/com.yourname/yourname
com.yourname you specify when you create a flutter project
yourname you specify when you create a flutter project

[darshankawar]

That seems to be a Windows path. I am using Mac and tried putting the file in project's root path and called SharedPreferences _preferences = await SharedPreferences.getInstance(); in main() function, but didn't see the issue. Maybe something is still missing.
Please be descriptive while providing details.

[krll-kov]

That seems to be a Windows path. I am using Mac and tried putting the file in project's root path and called SharedPreferences _preferences = await SharedPreferences.getInstance(); in main() function, but didn't see the issue. Maybe something is still missing.
Please be descriptive while providing details.

I have no idea where settings files for application is stored on macOs, but i specified, that i face issue on Windows

When you call

SharedPreferences _preferences = await SharedPreferences.getInstance();

method(and save at least one parameter), shared preferences creates a shared_preferences file on your device and stores all setting there. Find this file and replace it with the provided one. On windows this file is stored in %appdata%/com.yourdeveloper/yourappname

[stuartmorgan]

I am using Mac and tried [...]

Windows and macOS have completely unrelated implementations of preference storage. You cannot reproduce a Windows storage issue on macOS regardless of where you try to put that file.