我正在寻找一种方法来获得背景位置更新每n分钟在我的iOS应用程序。我使用的是iOS 4.3，解决方案应该适用于未越狱的iphone。
我尝试/考虑了以下选项:
CLLocationManager startUpdatingLocation/startMonitoringSignificantLocationChanges: This works in the background as expected, based on the configured properties, but it seems not possible to force it to update the location every n minutes
NSTimer: Does work when the app is running in the foreground but doesn't seem to be designed for background tasks
Local notifications: Local notifications can be scheduled every n minutes, but it's not possible to execute some code to get the current location (without the user having to launch the app via the notification). This approach also doesn't seem to be a clean approach as this is not what notifications should be used for.
UIApplication:beginBackgroundTaskWithExpirationHandler: As far as I understand, this should be used to finish some work in the background (also limited in time) when an app is moved to the background rather than implementing "long-running" background processes.
如何实现这些定期的后台位置更新?
以下是我使用的方法:
import Foundation
import CoreLocation
import UIKit
class BackgroundLocationManager :NSObject, CLLocationManagerDelegate {
static let instance = BackgroundLocationManager()
static let BACKGROUND_TIMER = 150.0 // restart location manager every 150 seconds
static let UPDATE_SERVER_INTERVAL = 60 * 60 // 1 hour - once every 1 hour send location to server
let locationManager = CLLocationManager()
var timer:NSTimer?
var currentBgTaskId : UIBackgroundTaskIdentifier?
var lastLocationDate : NSDate = NSDate()
private override init(){
super.init()
locationManager.delegate = self
locationManager.desiredAccuracy = kCLLocationAccuracyKilometer
locationManager.activityType = .Other;
locationManager.distanceFilter = kCLDistanceFilterNone;
if #available(iOS 9, *){
locationManager.allowsBackgroundLocationUpdates = true
}
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.applicationEnterBackground), name: UIApplicationDidEnterBackgroundNotification, object: nil)
}
func applicationEnterBackground(){
FileLogger.log("applicationEnterBackground")
start()
}
func start(){
if(CLLocationManager.authorizationStatus() == CLAuthorizationStatus.AuthorizedAlways){
if #available(iOS 9, *){
locationManager.requestLocation()
} else {
locationManager.startUpdatingLocation()
}
} else {
locationManager.requestAlwaysAuthorization()
}
}
func restart (){
timer?.invalidate()
timer = nil
start()
}
func locationManager(manager: CLLocationManager, didChangeAuthorizationStatus status: CLAuthorizationStatus) {
switch status {
case CLAuthorizationStatus.Restricted:
//log("Restricted Access to location")
case CLAuthorizationStatus.Denied:
//log("User denied access to location")
case CLAuthorizationStatus.NotDetermined:
//log("Status not determined")
default:
//log("startUpdatintLocation")
if #available(iOS 9, *){
locationManager.requestLocation()
} else {
locationManager.startUpdatingLocation()
}
}
}
func locationManager(manager: CLLocationManager, didUpdateLocations locations: [CLLocation]) {
if(timer==nil){
// The locations array is sorted in chronologically ascending order, so the
// last element is the most recent
guard let location = locations.last else {return}
beginNewBackgroundTask()
locationManager.stopUpdatingLocation()
let now = NSDate()
if(isItTime(now)){
//TODO: Every n minutes do whatever you want with the new location. Like for example sendLocationToServer(location, now:now)
}
}
}
func locationManager(manager: CLLocationManager, didFailWithError error: NSError) {
CrashReporter.recordError(error)
beginNewBackgroundTask()
locationManager.stopUpdatingLocation()
}
func isItTime(now:NSDate) -> Bool {
let timePast = now.timeIntervalSinceDate(lastLocationDate)
let intervalExceeded = Int(timePast) > BackgroundLocationManager.UPDATE_SERVER_INTERVAL
return intervalExceeded;
}
func sendLocationToServer(location:CLLocation, now:NSDate){
//TODO
}
func beginNewBackgroundTask(){
var previousTaskId = currentBgTaskId;
currentBgTaskId = UIApplication.sharedApplication().beginBackgroundTaskWithExpirationHandler({
FileLogger.log("task expired: ")
})
if let taskId = previousTaskId{
UIApplication.sharedApplication().endBackgroundTask(taskId)
previousTaskId = UIBackgroundTaskInvalid
}
timer = NSTimer.scheduledTimerWithTimeInterval(BackgroundLocationManager.BACKGROUND_TIMER, target: self, selector: #selector(self.restart),userInfo: nil, repeats: false)
}
}
我像这样在AppDelegate中开始跟踪:
BackgroundLocationManager.instance.start()
我使用了xs2bush获取间隔的方法(使用timeIntervalSinceDate)，并对其进行了一点扩展。我想确保我得到了我所需要的精度，同时我也没有因为保持gps收音机开得太久而耗尽电池。
我保持位置运行持续与以下设置:
locationManager.desiredAccuracy = kCLLocationAccuracyThreeKilometers;
locationManager.distanceFilter = 5;
这是一个相对低的电池消耗。当我准备好获得下一个周期性位置读数时，我首先检查位置是否在我期望的精度范围内，如果是，然后使用该位置。如果不是，那么我用这个来提高准确性:
locationManager.desiredAccuracy = kCLLocationAccuracyNearestTenMeters;
locationManager.distanceFilter = 0;
get my location and then once I have the location I turn the accuracy back down again to minimize the drain on the battery. I have written a full working sample of this and also I have written the source for the server side code to collect the location data, store it to a database and allow users to view gps data in real time or retrieve and view previously stored routes. I have clients for iOS, android, windows phone and java me. All clients are natively written and they all work properly in the background. The project is MIT licensed.
iOS项目的目标是iOS 6，使用iOS 7的基础SDK。你可以在这里得到代码。
如果你看到任何问题，请在github上提交一个问题。谢谢。
现在iOS6已经发布了，永远运行位置服务的最好方法是……
- (void)applicationWillResignActive:(UIApplication *)application
{
/*
Sent when the application is about to move from active to inactive state. This can occur for certain types of temporary interruptions (such as an incoming phone call or SMS message) or when the user quits the application and it begins the transition to the background state.
Use this method to pause ongoing tasks, disable timers, and throttle down OpenGL ES frame rates. Games should use this method to pause the game.
*/
NSLog(@"to background");
app.isInBackground = TRUE;
UIApplication *app = [UIApplication sharedApplication];
// Request permission to run in the background. Provide an
// expiration handler in case the task runs long.
NSAssert(bgTask == UIBackgroundTaskInvalid, nil);
bgTask = [app beginBackgroundTaskWithExpirationHandler:^{
// Synchronize the cleanup call on the main thread in case
// the task actually finishes at around the same time.
dispatch_async(dispatch_get_main_queue(), ^{
if (bgTask != UIBackgroundTaskInvalid)
{
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}
});
}];
// Start the long-running task and return immediately.
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
// Do the work associated with the task.
locationManager.distanceFilter = 100;
locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
[locationManager startMonitoringSignificantLocationChanges];
[locationManager startUpdatingLocation];
NSLog(@"App staus: applicationDidEnterBackground");
// Synchronize the cleanup call on the main thread in case
// the expiration handler is fired at the same time.
dispatch_async(dispatch_get_main_queue(), ^{
if (bgTask != UIBackgroundTaskInvalid)
{
[app endBackgroundTask:bgTask];
bgTask = UIBackgroundTaskInvalid;
}
});
});
NSLog(@"backgroundTimeRemaining: %.0f", [[UIApplication sharedApplication] backgroundTimeRemaining]);
}
就像这样测试:
我打开应用程序，进入后台，几分钟后开车。然后我回家1小时，再次开始移动(没有再次打开应用程序)。重新开始定位。然后停了两个小时，又重新开始。一切都好了……
不要忘记在iOS6中使用新的位置服务
- (void)locationManager:(CLLocationManager *)manager didUpdateLocations:(NSArray *)locations
{
CLLocation *loc = [locations lastObject];
// Lat/Lon
float latitudeMe = loc.coordinate.latitude;
float longitudeMe = loc.coordinate.longitude;
}
