Migrate user account management to UserAccountManager

[ezaquarii]

Situation

Currently user account can be represented by 4 different types:

• android.accounts.Account
• com.owncloud.android.lib.common.OwnCloudAccount
• String id
• int id

Accounts are being juggled in activities that try to track which account is currently active and perform ad-hoc reinitialization of UI on change.

The logic responsible for reconciliation of currently selected account and UI state is virtually impossible to track due to large amount of flags, conditions and out-of-band state modification.

Additionally, we discovered some issues with android account manager, causing accounts to disappear from the android.accounts.AccountManager on phones that allow installing the application on external storage (despite we forbid it in the manifest).

Solution

1. Make UserAccountManager a single point of truth regarding currently selected account
2. Eliminate ad-hoc UI patching in life cycle callbacks
3. Seal OwnCloudAccount and Account behind new unified interface
4. Migrate application components to new unified account type

No visible user impact, or impact minimized up to this point.

5. Make decision about new account manager implementation (platform? custom? library? app? sso?)

Roadmap

Due to current state of code, extensive refactoring and cleanup around account handling is necessary, as it contains too much state mutation dispersed through many functional areas.
Managing risk in such environment is not economical.

Proposal (incomplete):

• Deprecate setAccount and onAccountSet logic: Deprecate setAccount logic and remove accounWasSet flag #4677
• Remove deprecated onAccountSet callback from activities: Remove onAccountSet from UploadPathActivity  #4685 Remove onAccountSet from image and video preview activities #4686 Remove onAccountSet from UploadFilesActivity #4687 Remove onAccountSet from ShareActivity #4688 Remove onAccountSet from FolderPickerActivity #4689 Remove onAccountSet from FileDisplayActivity #4693 Remove onAccountSet from ConflictsResolveActivity #4694 Remove onAccountSet from ReceiveExternalFilesActivity #4700
• Eliminate account status flags from BaseActivity and derived classes Eliminate account status flags from BaseActivity #4710
• Refactor all activities performing or reacting to account switch to stop using setAccount and manually calling onAccountSet callback out of band. Remove out of band setAccount/onAccountSet calls #4713
• Extend UserAccountManager with notification API, allowing UI layer to react on account swap
• Finish activities stack and restart with new account instead of trying to switch internal state
  Enable assumption that account cannot change while being inside lifecycle activity.
• Start migrating to new account type (details to follow...)

[tobiasKaminsky]

Very good approach!
I guess the idea of OwnCloudAccount is to handle the most basic infos within library, so that other apps can also use this. Something similar is OCFile (in our app) vs RemoteFile (in library) for representing a server file.