监控iPhone上的电池电量

Question

I'm using the basic battery monitoring code on iOS and I've read somewhere that it drains battery to do so.

UIDevice *device = [UIDevice currentDevice];
    device.batteryMonitoringEnabled = YES;
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(batteryChanged) name:@"UIDeviceBatteryLevelDidChangeNotification" object:device];

I can't really find any good reference with actual data on this.

Is it really bad to check the changes in battery level? What other possibilities do I have? I would like to do much less treatment when the battery is low so that I don't finish it off.

Answer 1

Use this:

 UIDevice *myDevice = [UIDevice currentDevice];
 [myDevice setBatteryMonitoringEnabled:YES];
 double batLeft = (float)[myDevice batteryLevel] * 100;

Answer 2

I can think that the continous battery level monitoring is expensive. You may want to not monitor the battery continously .

Set a timer to every 5 minutes. In the tick method, set monitoring to YES, get level, then set monitoring to NO again. Don't need to subscribe to any notifications this way.

You may increase the interval below 20% battery, or so.

-(void)tick:(NSTimer*) timer
{
    [[UIDevice currentDevice] setBatteryMonitoringEnabled:YES];
    self.batteryPercentace = [[UIDevice currentDevice] batteryLevel];
    [[UIDevice currentDevice] setBatteryMonitoringEnabled:NO];
}

I'm not sure if it needs to be monitored at all, you may try out just simply read battery level.