Tuesday 29 October 2013

Droidcon 2013: App to App — design & surface local APIs

Ty Smith, Twitter (ex-Evernote) @tsmith

  • e.g. Samsung Note S Note app — locally synced with S Note grouping in built-in Evernote
  • tapping on a note in Evernote, opens it in S Note; then back button goes back to Evernote


  • when sharing content to another activity, need to provide URI permission
  • when offering edit, you shouldn’t send your original file
    • the third party might crash, corrupt, etc
  • also can’t rely on setResult
  • user might hit back and think their changes will be saved
  • set last modified — when activity returns can check to see if changed — then offer user to save if they want

content providers

  • can provide temporary permissions to access provider in an intent
  • can pass through file handles

account manager

  • see an example in the open source github app
  • can request an authenticated token
  • makes accounts visible to user in a standard place
  • can do OAuth1 or 2
  • has method to refresh OAuth2 token automatically

sync adapter

  • does a lot of management for you automatically (network, battery)
  • again, can expose to third parties
  • can be scheduled & started with cloud messaging
  • requires content provider & account manager
  • but watch out for all the syncs coming at once
    • especially as networks often send out heartbeats on the hour every hour
    • devices wake up and think: I might as well sync now…
    • Evernote received DDoS load spikes…
  • so add a jitter to the sync period (random 1hr -> 1hr5min)
  • also add a “wait until” in the sync adapter — do your own checking

bound service

  • much stronger contract than others
  • other apps need to include your AIDL source code
  • example: plugins for DashClock


  • testing is hard
    • use mock integrations
    • hard to debug integrations
  • add analytics to the lower level components so you know what’s going on
    • might want to consider rate limiting
  • use crash reporting (plug for crashlytics, now owned by twitter)

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