NSUserDefault 更新公式

Question

对如何通过 NSUserDefault 更新我的公式有疑问。所以我有两个文本字段需要让我的公式保持最新。所以用户在那里输入数字（值）然后这些数字需要进入我的公式，但公式只显示距离值:)。

Answer 1

我对您的代码进行了一些更改。这是我的.h 文件和.m 文件。试试这个。现在我也不明白你想找出什么，但这段代码给我的值不是nan。在编写代码时，不要忘记以小写字母开头变量名，这是一种标准方式。如果您将变量设置为属性，也可以使用self。

ViewController.h

#import <UIKit/UIKit.h>
#import <MapKit/MapKit.h>
#import <CoreLocation/CoreLocation.h>

@interface ViewController : UIViewController
<UITextFieldDelegate,CLLocationManagerDelegate>{
    IBOutlet MKMapView *mapView;
    IBOutlet UITextField *textGas;
    IBOutlet UITextField *textMoney;
    IBOutlet UITextField *textTotal;
    IBOutlet UITextField *textDistance;
}

@property (nonatomic, retain) CLLocationManager *locationManager;
@end

ViewController.m

 #import "ViewController.h"



    @interface ViewController ()
    {
        double totalDistance;
        float gas,money;
    }
    @end

    @implementation ViewController
    @synthesize locationManager;


    - (void)viewDidLoad
    {
        [super viewDidLoad];
        self.locationManager = [[CLLocationManager alloc] init];
        self.locationManager.delegate = self;
        self.locationManager.desiredAccuracy = kCLLocationAccuracyHundredMeters;
        [self.locationManager startUpdatingLocation];

//set default value for Gas
        if (![[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"]) {
            [[NSUserDefaults standardUserDefaults] setObject:@"1.0" forKey:@"Gas"];
            [[NSUserDefaults standardUserDefaults] synchronize];
        }

//set default value for Money
        if (![[NSUserDefaults standardUserDefaults] objectForKey:@"Money"]) {
            [[NSUserDefaults standardUserDefaults] setObject:@"1.0" forKey:@"Money"];
            [[NSUserDefaults standardUserDefaults] synchronize];
        }

        gas = [[[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"] floatValue];
        money =  [[[NSUserDefaults standardUserDefaults] objectForKey:@"Money"] floatValue];

        textGas.text = [NSString stringWithFormat:@"%.1f",gas];
        textMoney.text = [NSString stringWithFormat:@"%.1f",money];

        // Do any additional setup after loading the view, typically from a nib.
    }

    -(void)viewDidAppear:(BOOL)animated
    {
        [super viewDidAppear:animated];
        if ([[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"])
            textGas.text = [[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"];
        else
            textGas.text = @"0";//set default value

        if ([[NSUserDefaults standardUserDefaults] objectForKey:@"Money"])
            textMoney.text = [[NSUserDefaults standardUserDefaults] objectForKey:@"Money"];
        else
            textMoney.text = @"0.01";//set default value



    }

    -(void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
    {
        [textMoney resignFirstResponder];
        [textGas resignFirstResponder];
    }

    - (void)alertView:(UIAlertView *)alertView didDismissWithButtonIndex:(NSInteger)buttonIndex
    {
        if (buttonIndex == 1)
        {
            exit(0);
        }
        if (buttonIndex == 0) {
            [self.locationManager stopUpdatingLocation];
            mapView.showsUserLocation = NO;
        }

    }
    #pragma mark - UITextFieldDelegate
    -(void)textFieldDidEndEditing:(UITextField *)textField
    {

        if ([textField.text intValue] == 0) {
            textGas.text = [NSString stringWithFormat:@"%.1f",gas];
            textMoney.text = [NSString stringWithFormat:@"%.1f",money];
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@""
                                                            message:@"Value cann't be zero."
                                                           delegate:self
                                                  cancelButtonTitle:@"OK"
                                                  otherButtonTitles:nil];
            [alert show];
            alert = nil;
            return;
        }

        if (![textField.text length]) {
            textGas.text = [NSString stringWithFormat:@"%.1f",gas];
            textMoney.text = [NSString stringWithFormat:@"%.1f",money];
            UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@""
                                                            message:@"Value cann't be empty."
                                                           delegate:self
                                                  cancelButtonTitle:@"OK"
                                                  otherButtonTitles:nil];
            [alert show];
            alert = nil;
            return;
        }

        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        if (textField == textGas) {
            [defaults setObject:textGas.text forKey:@"Gas"];
            gas = [textGas.text floatValue];
        }
        else if (textField == textMoney)
        {
            [defaults setObject:textMoney.text forKey:@"Money"];
            money = [textMoney.text floatValue];
        }
        [defaults synchronize];
    }

    - (BOOL) textFieldShouldReturn:(UITextField *)textField
    {
        [textField resignFirstResponder];
        return YES;
    }

    #pragma mark -
    #pragma mark CLLocationManagerDelegate Methods

    - (void)locationManager:(CLLocationManager *)manager
        didUpdateToLocation:(CLLocation *)newLocation
               fromLocation:(CLLocation *)oldLocation {
        {
            // Zoom to the current user location.
            MKCoordinateRegion userLocation = MKCoordinateRegionMakeWithDistance(newLocation.coordinate, 1200.0, 1200.0);
            [mapView setRegion:userLocation animated:NO];
            mapView.showsUserLocation = YES;
        }



        if (!oldLocation)
            totalDistance = 0.0;
        else
            totalDistance += [newLocation distanceFromLocation:oldLocation];


        double distance = totalDistance*0.00062137119;
        textTotal.text = [[ NSString alloc] initWithFormat:@"$%.2f", distance/gas*money];
        textDistance.text = [NSString stringWithFormat:@"%.2f Miles", distance];

    }


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

模拟器中的结果是

不要忘记从界面生成器连接delegates 和IBOutlet。

Answer 2

我认为问题可能出在这里：

int gas = [[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"];
int money =  [[NSUserDefaults standardUserDefaults] objectForKey:@"Money"];

您直接从您的textField.text 写出您的NSUserDefaults，通常使用0.00 格式，但您正在以int 的形式读取它。它可能存储为NSString。您应该将其存储为NSNumber。

进入：

NSNumber *foo = [NSNumber numberWithInteger:TextGas.text.integerValue];
NSNumber *bar = [NSNumber numberWithDouble:TextMoney.text.doubleValue];    
[defaults setObject:foo forKey:@"Gas"];
[defaults setObject:bar forKey:@"Money"];

出来：

NSNumber *gas = [[NSUserDefaults standardUserDefaults] objectForKey:@"Gas"];
NSNumber *money =  [[NSUserDefaults standardUserDefaults] objectForKey:@"Money"];
gas.integerValue;
money.doubleValue;