iOS从后台重新检查加载位置 [英] iOS re-check location on load from background

问题描述

目前，我正在使用 viewDidLoad UIViewController 的方法来启动 CLLocationManager 并获取当前位置。一旦我的位置与我想要的精度相匹配，我就会向我的Web服务请求获取结果并将其转储到 UITableView 中。

我的问题是关闭应用程序时（尽管它仍在后台运行）。如果您要开车去另一个城镇，重新打开应用程序，数据不会更新，并继续显示您旧位置的结果。

基本上当从后台加载 UIViewController ，我需要能够检查用户的位置，如果它们移动了很长的距离，请更新我的 UITableView 。

然而，因为的 viewDidAppear > UIViewController 在从后台加载应用程序时不会触发，我不确定可以使用哪种方法。

我是意识到 stopMonitoringSignificantLocationChanges 方法会在找到新位置时唤醒您的应用程序。然而，这似乎有点OTT，因为我只需要知道一旦应用程序已经加载。

有没有其他选择使用 stopMonitoringSignificantLocationChanges

code>方法

解决方案

您可以注册以接收 -viewDidLoad <从UIApplication的通知/ code>。您可能对 UIApplicationDidBecomeActiveNotification 感兴趣。注册通知很简单。

   - （void）viewDidLoad 
 {
 [super viewDidLoad]; 
 [[NSNotificationCenter defaultCenter] addObserver：self selector：@selector（applicationDidBecomeActive :) name：UIApplicationDidBecomeActiveNotification object：nil]; 
 
  

在 -viewDidLoad 我们添加自己作为 UIApplicationDidBecomeActiveNotification 并指定当接收到该特定的通知时要调用的选择器。

的观察者

  - （void）applicationDidBecomeActive：（NSNotification *）notification 
 {
 //启动CLLocationManager 
 [self updateCurrentLocation]; 
} 
 
  - （void）viewDidUnload 
 {
 [super viewDidUnload]; 
 [[NSNotificationCenter defaultCenter] removeObserver：self name：UIApplicationDidBecomeActiveNotification object：nil]; 
} 
  

最后，请记住在视图卸载时以通知的观察者的身份。以这种方式平衡你的addObserver / removeObserver调用到NSNotificationCenter是一个好习惯。

I'm building an app which displays result data based on your current location.

At the moment, I'm using the viewDidLoad method of a UIViewController to start the CLLocationManager and getting the current location. Once I have the location that matches the accuracy I desire, I do a request to my web service to get the results and dump it into a UITableView.

My problem is that when you close the app (although it's still running in the background). If you were to drive to another town, re-open the app, the data doesn't get updated and continues to show the results from your old location.

Basically when the UIViewController loads from the background, I need to be able to check the users location, and if they have moved a significant distance, update the contents of my UITableView.

However, because the viewDidAppear of the UIViewController isn't triggered when you load the app from the background, I'm not sure which method I can use.

I am aware of the stopMonitoringSignificantLocationChanges method which wakes up your app when a new location is found. However, this seems a little OTT because I only need to know once the app has loaded.

Is there any alternative to using the stopMonitoringSignificantLocationChanges method?

解决方案

You could register to receive notifications from UIApplication in -viewDidLoad. You may be interested in UIApplicationDidBecomeActiveNotification. Registering for notifications is easy.

- (void)viewDidLoad
{
    [super viewDidLoad];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(applicationDidBecomeActive:) name:UIApplicationDidBecomeActiveNotification object:nil];
}

In -viewDidLoad we add ourselves as an observer of the UIApplicationDidBecomeActiveNotification and specify a selector to be invoked when that particular notification is received.

- (void)applicationDidBecomeActive:(NSNotification *)notification
{
    // Kick off your CLLocationManager
    [self updateCurrentLocation];
}

- (void)viewDidUnload
{
    [super viewDidUnload];
    [[NSNotificationCenter defaultCenter] removeObserver:self name:UIApplicationDidBecomeActiveNotification object:nil];
}

Finally, remember to remove yourself as an observer for this notification when the view unloads. It's good practice to balance your addObserver/removeObserver calls to NSNotificationCenter in this way.

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