[笔记] 使用 CLLocationManager 实现 RunKeeper

这篇难度系数极低，主要关于如何维护使用者已经跑出的距离(distance 变量)……
算两个CLLocation之间的距离本来想用一个地球半径相关复杂公式算的，但是既然有现成的，还是省省吧……

用这个初始化CLLocationManager：

- (void)startLocationUpdates
{
    // Create the location manager if this object does not
    // already have one.
    if (self.locationManager == nil) {
        self.locationManager = [[CLLocationManager alloc] init];
    }
 
    self.locationManager.delegate = self;
    self.locationManager.desiredAccuracy = kCLLocationAccuracyBest;
    self.locationManager.activityType = CLActivityTypeFitness;
 
    // Movement threshold for new events.
    self.locationManager.distanceFilter = 10; // meters
 
    [self.locationManager startUpdatingLocation];
}

用这段更新已经跑出的距离：

- (void)locationManager:(CLLocationManager *)manager
     didUpdateLocations:(NSArray *)locations
{
    for (CLLocation *newLocation in locations) {
        if (newLocation.horizontalAccuracy < 20) {
 
            // update distance
            if (self.locations.count > 0) {
                self.distance += [newLocation distanceFromLocation:self.locations.lastObject];
            }
 
            [self.locations addObject:newLocation];
        }
    }
}

注意：在使用CLLocationManager时，需要在Supporting File 的 info.plist 中加这样两行，否则没有办法用（调了好久才发现，还没搞清楚为啥）。

<!-- for requestAlwaysAuthorization -->
    <key>NSLocationAlwaysUsageDescription</key>
    <string>Explain for what are you using the user location</string>
    <!-- for requestWhenInUseAuthorization -->
    <key>NSLocationWhenInUseUsageDescription</key>
    <string>Explain for what are you using the user location</string>

代码链接：https://gist.github.com/1992chenlu/2ec71e9dc5d3d6588160

Reference: http://www.raywenderlich.com/73984/make-app-like-runkeeper-part-1