Add update check mechanism in the Google Play build

[emanuele-f]

The recent issues with crashes in PCAPdroid 1.8.0 and the inability to delivery prompt fixes to the users, due to the reliance on unreliable and slow Google Play review process, make it necessary to create a secondary channel to deliver critical fixes to the users or even normal updates in the case of long-standing Google Play policy issues.

In the Google Play build, It's necessary to add a method to periodically check for updates and prompt the user to install them. Here is how it should work:

• PCAPdroid will periodically request a JSON file at pcapdroid.org, containing the info about the latest version
• the JSON contains:
  • version number, type of update (feature, bugfix, critical)
  • possibly a changelog for the user
  • an optional recheck interval, which will override the default interval in the client
• consider also including the ability to display a custom message to the user, even without a version change, to notify him of important stuff

[kevin0t]

The update check should be an opt-in requirement and possibly presented to the user as a checkbox in the on-boarding menu and in settings. As a user may not like an app calling home without them opting into it.

Also a consideration that an update notification to a google play user may confuse them as normaly they would update from playstore but playstore update may not be available at this time. Usually this app update notifications are required for apks installed from github or website apk.

Ideally changing distribution channel should not be recommended to normal users , unless a very critical bug fix is there or other critical issues pop-up.
Changing the distribution channel would also involve uninstalling the play build and then installing it from new source due to signature conflicts, which is not a user friendly experience.
Usually i would recommend users to stick to one distribution channel for security and convenience reasons.

Still this feature could be useful for other notifications as pointed out in your 3rd point.

[emanuele-f]

I would agree with your points, in particular regarding the calling home stuff. But if no uniquely identifiable data is exchanged (e.g. I would just send the PCAPdroid version), I think it could be acceptable. Also asking too many things to the user on the first start does not look a good idea. I would have a toggle in the settings "check for updates" which is enabled by default.

Changing the distribution channel would also involve uninstalling the play build and then installing it from new source due to signature conflicts

Actually the apk is still signed with my signature and the user can update normally, keeping his user data. The only thing is that he will get a warning from Google Play, telling him that the apk is from a different channel. Also I'm not sure if installing it would prevent the user from receiving auto-updates from Google Play (e.g. he may have to manually install new app updates from Google Play to enable auto-updates again).

Anyway, I still have some doubts on this feature, but I really want to prevent the same situation happening in the future. Maybe staged rollouts is just enough, as they give you the ability to stop a rollout if something critical is found. Overall I can just say that the apps review process on Google Play is a jungle, and it's impossible to know if and when an update will be accepted; even if it's just a single byte change, they may come out with a policy violation which takes weeks (hopefully just weeks) to understand how to fix.