iOS - 使用“设置”和“取消”按钮打开“位置服务” - “如何捕获取消”按钮单击

Question

When the user launches the app for the first time and attempts to login, they are prompted with the iOS dialog - "Turn On Location Services".

I need to capture when the user clicks "cancel". Is there a Notification sent? If so, what is its name? I've been unable to locate it.

The CLAUthorizationStatus is kCLAuthorizationDenied when Location Services are Disabled OR the user clicked "Don't allow". When the user clicks "Cancel", it does not fire the authorizationChange event. When user clicks "Cancel", the app just hangs.

Answer 1

Short answer: You can't catch that notification. You can infer about the user choice and act consequently by using CLLocationManager methods (the longer answer below).

Longer answer:

Firstly, welcome on Stack Overflow. Before kindly posing your question, and trying to be collaborative with people that are here to help, it's a good idea to search if somebody else previously posed the same question.

A brief search gave (just to mention some of them):

• How to handle “Cancel” button on Alert pop up for Location services
• How to get location services to reprompt the user for location permission if they accidentally refused it?
• locationManager:didFailWithError: not called if user Location Services are off
• How to prompt user to turn on Location Services…again
• How can I prompt the user to turn on location services after user has denied their use
• How to ask permission from user for second time to allow to access the current location?

Now, let's try to summarize them all, starting from iOS docs:

If your app relies on location services to function properly, you should include the UIRequiredDeviceCapabilities key in the app's Info.plist file. You use this key to specify the location services that must be present in order for your app to run. The App Store uses the information in this key from preventing users from downloading apps to devices that do not contain the listed features.

Important: If your app uses location services but is able to operate successfully without them, do not include the corresponding strings in the UIRequiredDeviceCapabilities key.

So, if your app really needs to access the user's position you should add location-services and eventually gps to UIRequiredDeviceCapabilities .

Then, somewhere in your code - when needed, you have to check if the location services are enabled.

[CLLocationManager locationServicesEnabled]

they may be disallowed for three reasons:

• The user can disable location services in the Settings app.
• The user can deny location services for a specific app.
• The device might be in Airplane mode and unable to power up the necessary hardware.

You are interested in the second case: the user refused to allow your app to use the location services.

Again, from the docs:

Important: In addition to hardware not being available, the user has the option of denying an application's access to location service data. During its initial uses by an application, the Core Location framework prompts the user to confirm that using the location service is acceptable. If the user denies the request, the CLLocationManager object reports an appropriate error to its delegate during future requests. You can also check the application's explicit authorization status using the authorizationStatus method.

[CLLocationManager authorizationStatus]

That may return:

• kCLAuthorizationStatusNotDetermined if the user has not yet made a choice regarding whether this application can use location services.
• kCLAuthorizationStatusRestricted this application is not authorized to use location services. The user cannot change this application's status, possibly due to active restrictions such as parental controls being in place.
• kCLAuthorizationStatusDenied The user explicitly denied the use of location services for this application or location services are currently disabled in Settings.
• kCLAuthorizationStatusAuthorized This application is authorized to use location services.

If [CLLocationManager locationServicesEnabled] returns NO and you attempt to start location services anyway (ie calling [locationManager startUpdatingLocation] ), the system prompts the user to confirm whether location services should be re-enabled. Given that location services are very likely to be disabled on purpose, the user might not welcome this prompt.

I suppose you know, and did all the previous steps (I'm only sure you checked the authorizationStatus ). You refused to show us the significant code of your app so I can only suppose the overall logic behind. Now you said your app hangs. This should be because you didn't catch the error properly? Catching the error is the way to re-prompt the user, if you wish.

After calling [locationManager startUpdatingLocation] , if not authorized, your delegate should define a locationManager:didFailWithError: in order to catch the kCLErrorDenied .

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error

You may show, at this point, a UIAlert to insist asking the user to give you access to its position, or trigger a change in the UI or whatever you like.

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Final notes

I hope you understand why I was asking for the code: the reason was to offer you an alternative solution instead of reply "You can't catch the 'Cancel' notification".

If this answer does not satisfy your question please elaborate why you need to catch the pushing of the "Cancel"/"Do not allow" button, so we can provide alternatives.

Clearly my advice is to not annoy people to death by continuously ask them for enabling location services if they don't want.

Post scriptum: Maybe that the answer looks pedantic and obvious in certain parts if not all to you, but we are here to provide answers also for future readers.