如何將座標保存到文本文件？

Question

我想在每次按下「Get My」時，將緯度/經度座標保存在「var/mobile/Documents」文件夾中的名爲「Location.txt」的文本文件中（該文件首先必須被創建）位置「按鈕，每次覆蓋舊的座標。這可能嗎？有人可以給我舉例說明如何做到這一點。謝謝。

#import "ViewController.h" 

@interface ViewController() 
@end 

@implementation ViewController { 
CLLocationManager *locationManager; 
} 

- (void)viewDidLoad { 
[super viewDidLoad]; 
// Do any additional setup after loading the view, typically from a nib. 
locationManager = [[CLLocationManager alloc] init]; 
} 

- (void)didReceiveMemoryWarning { 
[super didReceiveMemoryWarning]; 
// Dispose of any resources that can be recreated. 
} 

- (IBAction)getCurrentLocation:(id)sender { 
locationManager.delegate = (id)self; 
locationManager.desiredAccuracy = kCLLocationAccuracyBest; 

[locationManager startUpdatingLocation]; 
} 

#pragma mark - CLLocationManagerDelegate 

- (void)locationManager:(CLLocationManager *)manager didFailWithError:(NSError *)error 
{ 
NSLog(@"didFailWithError: %@", error); 
UIAlertView *errorAlert = [[UIAlertView alloc] 
          initWithTitle:@"Error" message:@"Failed to Get Your Location" delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil]; 
[errorAlert show]; 
} 

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation 
{ 
NSLog(@"didUpdateToLocation: %@", newLocation); 
CLLocation *currentLocation = newLocation; 

if (currentLocation != nil) { 
    _LongitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude]; 
    _LatitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude]; 
} 

// Stop Location Manager 
[locationManager stopUpdatingLocation]; 
} 

@end 

Answer 1

您可以創建一個NSString，讓您的應用知道如何閱讀。例如：

NSString *newLocString = [NSString stringWithFormat:@"%f,%f",currentLocation.coordinate.longitude, currentLocation.coordinate.latitude]; 
NSString *path = //File Path.txt 
NSError *error = nil; 
// Save string and check for error 
if (![newLocStrin writeToFile:path atomically:YES encoding:NSUTF8StringEncoding error:&error]) { 
    NSLog(@"An Error occurred: %@", error.localizedDescription); 
} 

然後像這樣閱讀：

NSString *path = //File Path.txt 
NSError *error = nil; 
NSString *location = [NSString stringWithContentsOfFile:path usedEncoding:NSUTF8StringEncoding error:&error]; 
if (!location) { 
    NSLog(@"Error reading location file: %@", error.localizedDescription); 
} 
else { 
    // Have read the string so now format it back 
    NSString *longitude = nil; 
    NSString *latitude = nil; 
    NSScanner *scanner = [NSScanner scannerWithString:location]; 
    [scanner scanUpToString:@"," intoString:&longitide]; 
    latitude = [location stringByReplacingOccurrencesOfString:[NSString stringWithFormat:@"%@,",longitude] withString:@""]; 
    NSLog(@"Location equals %f,%f", longitude.floatValue, latitude.floatValue); 
} 

這可能是更容易使用一個NSDictionary和保存無論對或NSUserDefaults的作爲的.plist文件：

NSDictionary *dict = @{@"Longitude":@(currentLocation.coordinate.longitude), @"Latitude":@(currentLocation.coordinate.latitude)}; 

然後以用戶默認值：

[[NSUserDefaults standardUserDefaults] setObject:dict forKey:@"Location"]; 
// To read... 
NSDictionary *locDict = [[NSUserDefaults standardUserDefaults] objectForKey:@"Location"]; 
float longitude = [[locDict objectForKey:@"Longitude"] floatValue]; 
// e.t.c 

要寫入.plist文件，請使用類似於上述NSString方法的NSDictionary的writeToFile: atomically:方法。

希望這足以完成工作！

編輯：所有的文件寫入方法覆蓋舊版本的文件。

編輯2：保存plist文件在你的代碼：

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation 
{ 
NSLog(@"didUpdateToLocation: %@", newLocation); 
CLLocation *currentLocation = newLocation; 

if (currentLocation != nil) { 
    _LongitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.longitude]; 
    _LatitudeLabel.text = [NSString stringWithFormat:@"%.8f", currentLocation.coordinate.latitude]; 
    NSDictionary *locDict = @{@"Long":@(currentLocation.coordinate.longitude),@"Lat":@(currentLocation.coordinate.latitude)}; 
    // Probably want to save the file in the Application Support directory 
    NSString *path = [[NSSearchPathForDirectoriesInDomains(NSApplicationSupportDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"location.plist"]; 
    if (![locDict writeToFile:path atomically:YES]) { 
     NSLog(@"An error occurred."); 
    } 
    // Or save to NSUserDefaults 
    [[NSUserDefaults standardUserDefualts] setObject:locDict forKey:@"Location"]; 
} 

// Stop Location Manager 
[locationManager stopUpdatingLocation]; 
}