HealthKit (iOS) won't deliver data in background (objC)

问题

We're currently trying to get HealthKit to work in the background, in order to deliver steps data to our server when the App is closed.

For experimental purposes we've created a brand new iOS project in XCode, enabled HealhtKit and all background modes in Compabilities. After that, we pretty much run the code (see further down).

So what happens first is that the app ofcourse asks for the permissions, which we grant. What we're expecting is that the app should keep deliver the steps data every hour, to the server. But it doesnt do that, it seems like the app cant do anything when it's not active.

The app only deliver data when it gets resumed or started, but not at all from the background (Soft-closed / Hard-closed)

appdelegate.m:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [self setTypes];
    return YES;
}


-(void) setTypes
{
    self.healthStore = [[HKHealthStore alloc] init];

    NSMutableSet* types = [[NSMutableSet alloc]init];
    [types addObject:[HKObjectType quantityTypeForIdentifier:HKQuantityTypeIdentifierStepCount]];

    [self.healthStore requestAuthorizationToShareTypes: types
                                             readTypes: types
                                            completion:^(BOOL success, NSError *error) {

                                                dispatch_async(dispatch_get_main_queue(), ^{
                                                    [self observeQuantityType];
                                                    [self enableBackgroundDeliveryForQuantityType];
                                                });
                                            }];
}

-(void)enableBackgroundDeliveryForQuantityType{
    [self.healthStore enableBackgroundDeliveryForType: [HKQuantityType quantityTypeForIdentifier: HKQuantityTypeIdentifierStepCount] frequency:HKUpdateFrequencyImmediate withCompletion:^(BOOL success, NSError *error) {
    }];
}


-(void) observeQuantityType{

    HKSampleType *quantityType = [HKSampleType quantityTypeForIdentifier:HKQuantityTypeIdentifierStepCount];

    HKObserverQuery *query =
    [[HKObserverQuery alloc]
     initWithSampleType:quantityType
     predicate:nil
     updateHandler:^(HKObserverQuery *query,
                     HKObserverQueryCompletionHandler completionHandler,
                     NSError *error) {

         dispatch_async(dispatch_get_main_queue(), ^{
             if (completionHandler) completionHandler();
             [self getQuantityResult];

         });
     }];
    [self.healthStore executeQuery:query];
}


-(void) getQuantityResult{

    NSInteger limit = 0;
    NSPredicate* predicate = nil;

    NSString *endKey =  HKSampleSortIdentifierEndDate;
    NSSortDescriptor *endDate = [NSSortDescriptor sortDescriptorWithKey: endKey ascending: NO];

    HKSampleQuery *query = [[HKSampleQuery alloc] initWithSampleType: [HKQuantityType quantityTypeForIdentifier:HKQuantityTypeIdentifierStepCount]
                                                           predicate: predicate
                                                               limit: limit
                                                     sortDescriptors: @[endDate]
                                                      resultsHandler:^(HKSampleQuery *query, NSArray* results, NSError *error){

                                                          dispatch_async(dispatch_get_main_queue(), ^{
                                                                // sends the data using HTTP
                                                              [self sendData: [self resultAsNumber:results]];

                                                          });
                                                      }];
    [self.healthStore executeQuery:query];
}

回答1:

I see something that might be causing an issue in your AppDelegate, particularly this line:

[[NSURLConnection alloc] initWithRequest:request delegate:self];

This is creating an NSURLConnection, but not starting it. Try changing it to this:

NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];
[connection start];

Edit: After taking a second look at the docs

They recommend setting up your observer queries in your application didFinishLaunchingWithOptions: method. In your code above, you set the HKObserverQuery up in the authorization handler, which is called on a random background queue. Try making this change to set it up on the main thread:

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    [self setTypes];
    [self observeQuantityType];
    return YES;
}

HKObserverQuery Reference

回答2:

I found this out a little while ago when talking to someone from Apple. Apparently you can't access HK data in the background if the device is locked:

NOTE

Because the HealthKit store is encrypted, your app cannot read data from the store when the phone is locked. This means your app may not be able to access the store when it is launched in the background. However, apps can still write data to the store, even when the phone is locked. The store temporarily caches the data and saves it to the encrypted store as soon as the phone is unlocked.

from: https://developer.apple.com/library/ios/documentation/HealthKit/Reference/HealthKit_Framework/

来源：https://stackoverflow.com/questions/27593429/healthkit-ios-wont-deliver-data-in-background-objc