ios UIDeviceBattery【电池的状态处理:电池状态获取及监测、电池电量获取及监测、低电量模式切换监测】

前言 需求:电量低于 <= 50 %进行报警 name:NSProcessInfoPowerStateDidChangeNotification UIDeviceBatteryLevelDidChangeNotification [[NSNotificationCenter defaultCenter] addObserverForName:UIDeviceBatteryLevelDidChangeNotification object:nil queue:[NSOperationQueue mainQueue] usingBlock:^(NSNot