import android.content.Intent;
import android.content.IntentFilter;
import android.os.BatteryManager;

static int androidGetBattery() {
  Intent batteryIntent = androidContext().registerReceiver(null, new IntentFilter(Intent.ACTION_BATTERY_CHANGED));
  int level = batteryIntent.getIntExtra(BatteryManager.EXTRA_LEVEL, -1);
  int scale = batteryIntent.getIntExtra(BatteryManager.EXTRA_SCALE, -1);

  // Error checking that probably isn't needed but I added just in case.
  if(level == -1 || scale == -1) {
      return -1;
  }

  return (int) (((float)level / (float)scale) * 100.0f);
}

Began life as a copy of #1004076