Building Battery-Conscious Apps

Das ist mein Konspekt von dem Online-Kurs Android Development: Building Battery-Conscious Apps

…

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/principles-of-battery-conscious-apps

Wake-Up has costs:

• CPU on
• Screen on
• Data (Wi-Fi or cellular) on

Official documentation: http://developer.android.com/topic/performance/power/#lazy

Smart Design (aka Lazy First design)

1. Reduce (e.g. resolution of photos for upload/download)
2. Defer
3. Coalesce (combining transactions to a “batch”)
4. Rethink

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/considerations-for-using-alarmmanager

• Schedule asynchronous operations
• Time-based
• Single or repetitive
• Perfect for exact time-based scheduling
• Periodic background tasks
• Combined effects cause battery drain
• Wake up has a cost

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/pitfalls-of-poor-alarmmanager-usage

1. Background network operations (AlarmManager does not have intelligent dispatch logic)
2. Alarms does not survive reboots (Extra logic required, e.g. BroadcastReceiver)
3. Exact Alarm may not be exact
   • Since Kitkat
   • setExactAndAllowWhileIdle → is affected by Doze Mode
4. Doze Mode introduces complexity (e.g. setExact can drift)

Takeaways:

• Avoid network operations
• Doze Mode affects AlarmManager
• Maybe better would be to switch to JobScheduler (because it is not time driven, but event driven)

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/considerations-for-using-background-started-services

• Background Started Services
  • typically long running operations with no UI (e.g. music player)
  • started via an API call
  • contract:
    • client calls Context.startService()
    • system calls Service.onStartCommand()
    • Service stops
      • service stops itself with Service.stopSelf()
      • OR:
      • client calls Service.stopService()
  • System requires service to remain running until stopped explicitly
  • Note: in production IntentService would be better as simple Service
• When to Use Background Started Service
  • intense, low-priority tasks not noticed by user
  • irregular, user-driven background tasks
  • stateless reentrant operations (e.g. refreshing news content)
  • work queue processor pattern (IntentService)
  • Note: if task is periodic scheduled job may be a better choice

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/pitfalls-of-poor-background-started-service-usage

• Pitfall 1: Android
  • Google is tightening restrictions
• Pitfall 2: No Rules or Policy Support
  • Connectivity checks
    • Active connection
    • Airplane mode
    • Remote server availability
  • Appropriateness checks
    • Battery level
    • Roaming status
    • Metered connection
  • Back off and retry policy
    • Retry when?
    • Retry how often?
• Pitfall 3: No intelligent batching
  • No batching unlike AlarmManager
  • Cannot differentiate between services and different apps
• Pitfall 4: Other reasons
  • Idle processes are wasteful
  • Fragmentation is a problem

• Takeaway
  • Use job scheduler for most cases
  • Use started services for simple one-shot background tasks

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/a-review-of-broadcast-receivers

• Introduction to Broadcast Receivers
  • support event-driven programming
  • used for many system events
  • Interprocess communication (IPC)
  • delivered via Intent
  • Intents specify actions and optional extras
  • should extend BroadcastReceiver
  • should implement onReceive()

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/registering-a-broadcast-receiver

• Statically registered (AndroidManifest.xml)
• Dynamically registered (through the Java code)

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/triggering-a-broadcast-receiver

Two posibilities to trigger a broadcast receiver:

1. Call implicit trigger
   • Candidates matched via filter
   • Recipients unknown until match
   • Recipients may change
2. Explicit trigger
   • Invocation via code
   • Recipients known
   • Recipients never change

• Any app can define its own intent

Example of triggering explicitly:

Intent i = new Intent("my.action.name")
                .setComponent(new ComponentName(context.getPackageName(), className));
context.setBroadcast(i);

https://www.linkedin.com/learning/android-development-building-battery-conscious-apps/considerations-of-static-implicit-broadcast-receivers

This post scriptum is not based on the online course, but on other articles.

From Android Battery Optimization for Avoiding Doze Mode and App Standby

if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
    Intent intent = new Intent();
    String packageName = getPackageName();
    PowerManager pm = (PowerManager) getSystemService(POWER_SERVICE);
    if (!pm.isIgnoringBatteryOptimizations(packageName)) {
        intent.setAction(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS);
        intent.setData(Uri.parse("package:" + packageName));
        startActivity(intent);
    }
}