（七十五）CoreLocation（一）在iOS7和iOS8設備上獲取受權

蘋果在iOS8上更新了CoreLocation的受權獲取方式，在原來的基礎上，不只須要調用受權函數，還須要對info.plist進行相應的配置。

在iOS上獲取經緯度使用的是CoreLocationManager，它來自CoreLocation.framework框架，使用時應當包含框架的總頭文件：

#import <CoreLocation/CoreLocation.h>

通常是先建立管理者，而後成爲其代理，對於iOS7，直接調用 startUpdatingLocation便可開始監聽，而對於iOS8，還須要調用一個方法進行受權，根據使用情況的不一樣，有兩種受權，分別是使用時獲取位置和持續獲取位置，根據須要的不一樣進行調用：

[self.manager requestAlwaysAuthorization];
[self.manager requestWhenInUseAuthorization];

通常直接獲取第一個便可，應用面更廣。

除此以外，在info.plist中加入兩個鍵，值爲string，string中的內容就是請求受權時顯示的說明：

對應於兩種受權，有NSLocationWhenInUseUsageDescription和NSLocationAlwaysUsageDescription兩個鍵。

在每次開啓應用時，會調用一個代理方法來判斷受權狀態：經過這個方法判斷是否受權成功，若是成功則調用startUpdatingLocation來開始定位。

// 受權狀態發生改變時調用
-(void)locationManager:(CLLocationManager *)manager didChangeAuthorizationStatus:(CLAuthorizationStatus)status{
    /*
    typedef NS_ENUM(int, CLAuthorizationStatus) {
        // User has not yet made a choice with regards to this application
        kCLAuthorizationStatusNotDetermined = 0,
        
        // This application is not authorized to use location services.  Due
        // to active restrictions on location services, the user cannot change
        // this status, and may not have personally denied authorization
        kCLAuthorizationStatusRestricted,
        
        // User has explicitly denied authorization for this application, or
        // location services are disabled in Settings.
        kCLAuthorizationStatusDenied,
        
        // User has granted authorization to use their location at any time,
        // including monitoring for regions, visits, or significant location changes.
        kCLAuthorizationStatusAuthorizedAlways NS_ENUM_AVAILABLE(NA, 8_0),
        
        // User has granted authorization to use their location only when your app
        // is visible to them (it will be made visible to them if you continue to
        // receive location updates while in the background).  Authorization to use
        // launch APIs has not been granted.
        kCLAuthorizationStatusAuthorizedWhenInUse NS_ENUM_AVAILABLE(NA, 8_0),
        
        // This value is deprecated, but was equivalent to the new -Always value.
        kCLAuthorizationStatusAuthorized NS_ENUM_DEPRECATED(10_6, NA, 2_0, 8_0, "Use kCLAuthorizationStatusAuthorizedAlways") = kCLAuthorizationStatusAuthorizedAlways
    };*/
    
    switch (status) {
        case kCLAuthorizationStatusAuthorizedAlways:
            NSLog(@"持續使用受權");
            [self.manager startUpdatingLocation];
            break;
        case kCLAuthorizationStatusAuthorizedWhenInUse:
            NSLog(@"使用中受權");
            [self.manager startUpdatingLocation];
            break;
        case kCLAuthorizationStatusDenied:
            NSLog(@"受權被拒絕");
            break;
        case kCLAuthorizationStatusNotDetermined:
            NSLog(@"等待用戶受權");
            break;
        default:
            break;
    }
    
    
}

由於iOS7直接開始獲取位置便可，所以應當對兩種系統區分對待，用UIDevice獲取到系統版本，針對不一樣的系統進行不一樣的處理，若是是iOS8之前的系統，直接開始獲取位置：

- (void)viewDidLoad {

    [super viewDidLoad];
    
    // 1.建立CoreLocationManager
    CLLocationManager *manager = [[CLLocationManager alloc] init];
    self.manager = manager;
    // 2.成爲其代理
    self.manager.delegate = self;
    
    if ([[UIDevice currentDevice].systemVersion doubleValue] >= 8.0) {
        [self.manager requestAlwaysAuthorization];
    }else{
        // iOS8之前直接開始定位
        [self.manager startUpdatingLocation];
    }
    
}

要判斷是否成功的開始定位，實現代理方法 locationManager: didUpdateLocations:來觀察。

有關經緯度、方向、區域判斷等請見下節。