added lock feature

[danger-ahead]

• tested on Android
• tested on iOS
• added all the necessary code changes for both Android and iOS for the feature to work

Lets the user to use biometrics as well as pin or pattern.
Also adds the ability to lock or unlock the app from the Profile section.

Uses shared_preferences to check if the user has turned on locking.
Uses local_auth for the actual authorisation feature to work.

Addresses #2

[danger-ahead]

Do not merge this now. It has a bug. Will fix this tomorrow.

[31Carlton7]

So far so good! However, is it possible that you could use hive instead of shared_preferences for local storage, as hive's performance is much better and I just recently migrated the app from using shared_preferences to hive.

[danger-ahead]

is it possible that you could use hive

Okay will be changing that too.

[danger-ahead]

@31Carlton7 Don't merge this PR yet. This needs further testing and polishing.

[danger-ahead]

@31Carlton7 Don't merge this PR yet. This needs further testing and polishing.

Hi @31Carlton7
Would you please test this PR on your emulator (or device)?

Actually I think it's much consistent to work with local_auth if we're working with a stateful widget. However, in our case, the root widget of our app is a stateless widget.
Though I think it's working fine. Let me know if you encounter any error or bug.
Also one possible fix could be migrating the root widget to a stateful widget (I might be wrong here, just learning Flutter).

[danger-ahead]

@31Carlton7 I tried to fix most of the bugs.

One still remains:

Here, the contents of the top most note remains visible prior to authorization. I'm not much well accustomed to state management. Perhaps this bug can be solved by delaying the render of home_view till authenticate() has returned true. This portion resides in home_view.dart.

Also you can now MERGE this PR.

[31Carlton7]

I'll take a look at it either tonight or tomorrow!

[danger-ahead]

I'll take a look at it either tonight or tomorrow!

I didn't change back to hive because only one pair of key-value is being used for the locking algorithm. And shared_preferences performs better when it comes to reading data. I found out about this from here.

[31Carlton7]

I just went through the code and tested it, and the feature doesn't work. None of the notes are locked, and it didn't exactly do anything. Please review your code and update the app to lock the notes and require password auth when trying to view a note.

[danger-ahead]

VID-20211117-WA0038.mp4

I tested this on multiple devices.
Which device are you using? And what's the error log?
Kindly upload the console log.

[danger-ahead]

@31Carlton7 awaiting your reply.