呼叫用戶座標，加載PHP文件，並在UIApplicationDidBecomeActiveNotification上更新UI

Question

我需要我的應用程序調用任何時間從前臺不「回來」的方法。我正在使用UIApplicationDidBecomeActiveNotification來完成此操作，如下所示。該方法似乎調用正確，因爲如果我在我的appReturnsActive方法中放置一個警報，它警報就好了。

但是，在appReturnsActive中，我試圖根據用戶的位置更新UI，而不是簡單的警報。我將用戶的地理座標傳遞給PHP文件，並返回1或0.如果PHP文件返回1，我想顯示按鈕1和2.如果PHP文件返回0，我想顯示按鈕3和2.

這似乎並沒有正確更新每次。這是因爲UI在應用程序有機會找到用戶的位置之前正在更新？任何幫助將是偉大的！

謝謝！

ViewDidAppear：當應用程序恢復時

[[NSNotificationCenter defaultCenter] addObserver:self 
selector:@selector(appReturnsActive) name:UIApplicationDidBecomeActiveNotification 
object:nil]; 

方法叫：

- (void)appReturnsActive{ 

NSString *userLatitude =[(AppDelegate *)[UIApplication sharedApplication].delegate 
getUserLatitude]; 

NSString *userLongitude =[(AppDelegate *)[UIApplication sharedApplication].delegate 
getUserLongitude]; 

NSString *placeLatitude = [[NSUserDefaults standardUserDefaults] 
           stringForKey:@"savedLatitude"];  

NSString *placeLongitude = [[NSUserDefaults standardUserDefaults] 
           stringForKey:@"savedLongitude"]; 

NSString *distanceURL = [NSString 
stringWithFormat:@"http://www.website.com/location.php? 
lat1=%@&lon1=%@&lat2=%@&lon2=%@",userLatitude, userLongitude, placeLatitude, 
placeLongitude]; 

NSData *distanceURLResult = [NSData dataWithContentsOfURL:[NSURL 
URLWithString:distanceURL]]; 

NSString *distanceInFeet = [[NSString alloc] initWithData:distanceURLResult 
encoding:NSUTF8StringEncoding]; 

if ([distanceInFeet isEqualToString:@"1"]) 
{ 
    UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 1" 
    style:UIBarButtonItemStyleBordered target:self action:@selector(buttoneOneAction)]; 
    self.navigationItem.rightBarButtonItem = btnGo; 
    [self.navigationItem.rightBarButtonItem setTintColor:[UIColor colorWithRed:44.0/255.0 
    green:160.0/255.0 blue:65.0/255.0 alpha:1.0]]; 

    UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 2" 
    style:UIBarButtonItemStyleBordered target:self action:@selector(buttonTwoAction)]; 
    self.navigationItem.rightBarButtonItem = btnGoTwo; 

    self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, btnGoTwo, 
    nil]; 
} 

if ([distanceInFeet isEqualToString:@"0"]) 
{ 
    UIBarButtonItem *btnGo = [[UIBarButtonItem alloc] initWithTitle:@"Button 3" 
    style:UIBarButtonItemStyleBordered target:self action:@selector(buttonThreeAction)]; 
    self.navigationItem.rightBarButtonItem = btnGo; 
    [self.navigationItem.rightBarButtonItem setTintColor:[UIColor colorWithRed:44.0/255.0 
    green:160.0/255.0 blue:65.0/255.0 alpha:1.0]]; 

    UIBarButtonItem *btnGoTwo = [[UIBarButtonItem alloc] initWithTitle:@"Button 2" 
    style:UIBarButtonItemStyleBordered target:self action:@selector(buttonTwoAction)]; 
    self.navigationItem.rightBarButtonItem = btnGoTwo; 

    self.navigationItem.rightBarButtonItems = [NSArray arrayWithObjects:btnGo, btnGoTwo, 
    nil]; 
} 

} 

緯度和經度的方法在AppDelegate中：

- (NSString *)getUserLatitude 
{ 
    NSString *userLatitude = [NSString stringWithFormat:@"%f", 
    locationManager.location.coordinate.latitude]; 
    return userLatitude; 
} 

- (NSString *)getUserLongitude 
{ 
    NSString *userLongitude = [NSString stringWithFormat:@"%f", 
    locationManager.location.coordinate.longitude]; 
    return userLongitude; 
} 

在應用程序委託

位置經理：

- (NSString *)getUserCoordinates 
{ 
    NSString *userCoordinates = [NSString stringWithFormat:@"latitude: %f longitude: %f", 
    locationManager.location.coordinate.latitude, 
    locationManager.location.coordinate.longitude]; 
    locationManager = [[CLLocationManager alloc] init]; 
    locationManager.distanceFilter = kCLDistanceFilterNone; // whenever we move 
    locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters; // 100 m 
    [locationManager startUpdatingLocation]; 

    return userCoordinates; 

} 

Answer 1

獲取用戶位置的過程是異步的，所以你需要更新獲取用戶的位置後，才UI。從您當前的實施中，UI可能會在獲取位置之前更新。

您需要實現位置管理的委託和使用NSNotificationCenter做的更新有，例如：

//iOS 5 and before 
- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation 
{ 
    self.currentLocation = newLocation; 
    [[NSNotificationCenter defaultCenter] postNotificationName:@"CurrentLocationObtained" object:nil]; 
} 

//iOS 6 
- (void)locationManager:(CLLocationManager *)manager 
    didUpdateLocations:(NSArray *)locations { 

    self.currentLocation = [locations objectAtIndex:0]; 
    [[NSNotificationCenter defaultCenter] postNotificationName:@"CurrentLocationObtained" object:nil]; 
} 

根據您當前的代碼，你需要設置的AppDelegate爲CLLocationManagerDelegate。然後，當你實例位置管理，設定的委託：

locationManager.delegate = self; 

看看這裏特別是關於如何正確設置委託的第一個答案：Set delegate of CLLocationManager (Two different ways, are they equal?)