iOS.Location-Based Service
基于位置区域的服务
1. 背景
Ref[1]
在iOS设备锁屏的状态下，App的icon会出现在屏幕的左下角。
iOS 8 Feature: Location-based Lockscreen App Shortcuts Appearing on iPhone
http://www.igeeksblog.com/ios-8-feature-location-based-lockscreen-app-shortcuts-appearing-on-iphone/
Can I get my iOS app to appear on the lower left corner of the lock screen?
http://stackoverflow.com/questions/25897219/can-i-get-my-ios-app-to-appear-on-the-lower-left-corner-of-the-lock-screen
2. 区域监控和iBeacon
Ref[1]
2.1 Core Location framework提供两种方式来检测(detect)一个用户进入和退出某个区域：
A) geographical region monitoring (iOS 4.0+ OS X v10.8+)
B) beacon region monitoring (iOS 7+)
geographical region is an area defined by a circle of a specified radius around a known point on the Earth’s surface.
beacon region is an area defined by the device’s proximity to Bluetooth low-energy beacons.
Apps can use region monitoring to be notified when a user crosses geographic boundaries or when
a user enters or exits the vicinity of a beacon.
In iOS, regions associated with your app are tracked at all times, including when the app isn’t running.
If a region boundary is crossed while an app isn’t running, that app is relaunched into the background to handle the event.
Similarly, if the app is suspended when the event occurs, it’s woken up and given a short amount of time (around 10 seconds)
to handle the event.
2.2 判断Region Monitoring(区域监控)是否可用
A) 设备没有必要的硬件来支持RM。
B) 用户拒绝App的使用RM的授权。
C) 用户在"设置"App中关闭了定位服务。
D) 用户在"设置"App中关闭了"后台App刷新"的功能。
E) 设备在Airplane模式时不能启动必须的硬件。
以上原因都会导致RM不可用。
在iOS 7.0+, 在监控区域之前调用isMonitoringAvailableForClass: and authorizationStatus(CLLocationManager)。
在之前的iOS中，调用regionMonitoringAvailable。
方法isMonitoringAvailableForClass:通过返回值来告诉App硬件是否支持某类的RM。如果返回YES, 进而调用
authorizationStatus来决定App是否已被授权使用定位服务。如果status是kCLAuthorizationStatusAuthorized，
则App可以接收"穿越边界"(boundary crossing)的通知。如果status是其它的值，则App不会收到这些通知。
"Finally, if your app needs to process location updates in the background, be sure to check the
backgroundRefreshStatus property of the UIApplication class. You can use the value of this property
to determine if doing so is possible and to warn the user if it is not. Note that the system doesn’t wake
your app for region notifications when the Background App Refresh setting is disabled globally
or specifically for your app." Ref[1]
2.3 监控地理区域 (Monitoring Geographical Regions)
Geographical region monitoring uses location services to detect entry and exit into known geographical locations.
2.3.1 定义一个被监控的地理区域
在监控地理区域之前，必须定义一个区域(region)并将它注册到系统中。
iOS 7.0+, 使用CLCircularRegion类来定义。在以前的iOS版本中，使用CLRegion类。
每个region包括定义地理区域的数据和唯一的一个ID。这个ID用来在App中来标识一个区域。
使用CLLocationManager的方法startMonitoringForRegion: 来注册区域。
Demo-1: Creating and registering a geographical region based on a Map Kit overlay
Monitoring of a geographical region begins immediately after registration for authorized apps.
However, don’t expect to receive an event right away, because only boundary crossings generate an event.
To check whether the user is already inside the boundary of a region, use the requestStateForRegion: method of the CLLocationManager class.
"Regions are a shared system resource, and the total number of regions available systemwide is limited.
For this reason, Core Location limits to 20 the number of regions that may be simultaneously monitored
by a single app. To work around this limit, consider registering only those regions in the user’s immediate vicinity.
As the user’s location changes, you can remove regions that are now farther way and add regions coming
up on the user’s path. If you attempt to register a region and space is unavailable, the location manager calls thelocationManager:monitoringDidFailForRegion:withError: method of its delegate with
thekCLErrorRegionMonitoringFailure error code."
2.3.2 处理穿越地理区域边界的事件
3. 监控Beacon区域
beacon由以下信息标识：
proximity UUID: a 128-bit value that uniquely identifies one or more beacons as a certain type or from a certain organization.
major value: is a 16-bit unsigned integer that can be used to group related beacons that have the same proximity UUID.
minor value: is a 16-bit unsigned integer that differentiates beacons with the same proximity UUID and major value.
一个beacon区域可以代表多个beacon。
(Note that although every beacon must advertise a proximity UUID, major and minor values are optional.)
3.1 定义被监控的beacon区域
定义beacon区域使用CLBeaconRegion类。
"Note that a region’s identifier is unrelated to the identifying information that a beacon advertises."
Demo-2: Creating and registering a beacon region
"When a user’s device detects a beacon that is advertising the identifying information defined by
the registered beacon region (proximity UUID, major value, and minor value), the system generates
an appropriate region event for your app."
3.2 处理Beacon区域的穿越边界事件
3.3 Determining the Proximity of a Beacon Using Ranging
startRangingBeaconsInRegion:
Demo-3: Determining the relative distance between a beacon and a device
4. 将iOS设备转换为iBeacon
Ref[1]
"Any iOS device that supports sharing data using Bluetooth low energy can be used as an iBeacon.
In Core Bluetooth, a peripheral is a device that advertises and shares data using Bluetooth low energy. Advertising your beacon’s data is the only way other devices can detect and range your beacon. " Ref[1]
Reference
1. <<Location and Maps Programming Guide>> Region Monitoring and iBeacon
https://developer.apple.com/library/mac/documentation/UserExperience/Conceptual/LocationAwarenessPG/RegionMonitoring/RegionMonitoring.html
2. iOS 8 pushes location context to a new level: lock screen notifications triggered by iBeacon
http://blog.estimote.com/post/97824495825/ios-8-pushes-location-context-to-a-new-level-lock
3. Core Bluetooth Programming Guide
Item
Region Monitoring: 区域监控，RM
