1. Monitoring battery power

2. overview Battery usage is critical on mobile apps Measuring energy usage is a bit tricky since many processes Android provides broadcast sticky intents on the battery level The intent contents various information about the battery state How can you get the current battery level? – Do you have to wait for a change in battery level to receive a new intent that contains the new information? – No, the OS generates a sticky intent, which will stay around until a new one is generated. – As soon as you register to get a battey level change intent, you will get the most recent intent. – After that, you will get the intents as they are generated If your app is able to get them?

3. Make a new app, BatteryLevelFun Add textView to UI, with Id textView1 In BatteryLevelFunActivity – Add member variable TextView textView; IntentFilter batteryLevelFilter = null; – In onCreate, add textView = (TextView)findViewById(R.id.textView1); //register to receive broadcast intents about battery level batteryLevelFilter = new IntentFilter(Intent.ACTION_BATTERY_CHANGED); – Make onResume @Override public void onResume() { – super.onResume(); – registerReceiver(batteryLevelReceiver, batteryLevelFilter); } – Make onPause @Override public void onPause() { – super.onPause(); – unregisterReceiver(batteryLevelReceiver); } – Object to receive broadcast intents BroadcastReceiver batteryLevelReceiver = new BroadcastReceiver() { – public void onReceive(Context context, Intent intent) { » processBatteryIntent(intent); – } };

4. Function to process battery intent DateTime lastTime = null; double lastLevel; public void processBatteryIntent(Intent intent) { – DateTime currentTime = new DateTime(); // needs joda time – String batteryStr = new String(); – int rawlevel = intent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1); – int scale = intent.getIntExtra(BatteryManager.EXTRA_SCALE, -1); – double level = -1; – if (rawlevel >= 0 && scale > 0) { level = (rawlevel * 100) / (double)scale; – } – double rate = 0; – if (lastTime!=null && lastLevel!=level) { rate = (level - lastLevel)/(currentTime.getMillis()-lastTime.getMillis())*1000.0; batteryStr += String.format("charging rate: %f ", rate); if (level>lastLevel) – batteryStr += String.format("fully charged in %f hours\n", (100-level)/rate/3600.0); else – batteryStr += String.format("fully discharged in %f hours\n", (level)/-rate/3600.0); – } – batteryStr += "current level: " + level + " last level: " + lastLevel + " "; – if (lastTime==null || lastLevel!=level) { lastTime = currentTime; lastLevel = level; – } – batteryStr += "\nbattery temperture: "+((double)intent.getIntExtra(BatteryManager.EXTRA_TEMPERATURE, - 1)/10.0) + " degrees C\n"; – int plugged = intent.getIntExtra(BatteryManager.EXTRA_PLUGGED, -1); – switch (plugged) { case 0: – batteryStr += "unplugged\n"; – break; case BatteryManager.BATTERY_PLUGGED_AC: – batteryStr += "Plugged into AC\n"; – break; case BatteryManager.BATTERY_PLUGGED_USB: – batteryStr += "Plugged into USB\n"; – break; default: batteryStr += "unknown plugged state\n"; – } – int health = intent.getIntExtra(BatteryManager.EXTRA_HEALTH, -1); – batteryStr += "battery health: "; – switch (health) { case BatteryManager.BATTERY_HEALTH_DEAD: – batteryStr += "dead\n"; break; case BatteryManager.BATTERY_HEALTH_GOOD: – batteryStr += "good\n"; break; case BatteryManager.BATTERY_HEALTH_OVER_VOLTAGE: – batteryStr += "over voltage\n"; break; case BatteryManager.BATTERY_HEALTH_OVERHEAT: – batteryStr += "overheat\n"; break; case BatteryManager.BATTERY_HEALTH_UNKNOWN: – batteryStr += "unknown\n"; break; case BatteryManager.BATTERY_HEALTH_UNSPECIFIED_FAILURE: – batteryStr += "some failure\n"; break; – } – int status = intent.getIntExtra(BatteryManager.EXTRA_STATUS, -1); – batteryStr += "battery status: "; – switch (status) { case BatteryManager.BATTERY_STATUS_CHARGING: – batteryStr += "charigng\n"; break; case BatteryManager.BATTERY_STATUS_DISCHARGING: – batteryStr += "discharging\n"; break; case BatteryManager.BATTERY_STATUS_FULL: – batteryStr += "full\n"; break; case BatteryManager.BATTERY_STATUS_NOT_CHARGING: – batteryStr += "not charing\n"; break; case BatteryManager.BATTERY_STATUS_UNKNOWN: – batteryStr += "unknown\n"; break; – } – int voltage = intent.getIntExtra(BatteryManager.EXTRA_VOLTAGE, -1); – batteryStr += "battery voltage: "+ voltage + "\n"; – String technology = intent.getStringExtra(BatteryManager.EXTRA_TECHNOLOGY); – batteryStr += "battery technology: "+ technology +"\n"; – boolean present = intent.getBooleanExtra(BatteryManager.EXTRA_PRESENT, false); – if (present) batteryStr += "battery is present\n"; – else batteryStr += "battery is not present\n"; – textView.setText(batteryStr); }

5. test Run it. Try plugging and unplugging usb cable It takes a while to get a new update Try registering broadcast receiver in onCreate and not in onResume and doing nothing in onPause. And then run it and back arrow – In onResume, delete registerReceiver(batteryLevelReceiver, batteryLevelFilter); – In onPause, delete unregisterReceiver(batteryLevelReceiver); – In onCreate, add registerReceiver(batteryLevelReceiver, batteryLevelFilter); – Run it, and use backward arrow. Might crash Will give error message about a problem with a broadcast receiver – The problem is that the broadcast receiver is registered, but the app is not running Get battery level immediately – In onCreate, add – Intent current = registerReceiver(null, batteryLevelFilter); – processBatteryIntent(current);