Question

我编写了以下代码来查找当前位置。当我在lat2下面打印logg2和NSLOg时，它运行良好并打印当前位置，但它没有为标签赋值。当我打印label时，该值为null。

我想访问方法didUpdateToLocation之外的lat2和logg2值。尽管如此，我无法在didUpdateToLocation方法之外访问这些值我已经全局声明了logg2和lat2。在此方法之外，它给出null值。我怎样才能做到这一点？这有什么问题？是否有任何示例代码或教程？

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil {
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) {
        // Custom initialization.
    }
    return self;
}

-(void)awakeFromNib {
    [self update];
}

- (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation
{
    if (wasFound) return;
    wasFound = YES;

    CLLocationCoordinate2D loc = [newLocation coordinate];

    lat2 = [NSString stringWithFormat: @"%f", loc.latitude];
    logg2= [NSString stringWithFormat: @"%f", loc.longitude];
    NSLog(@"latitude is %@",lat2);
    NSLog(@"longitude is  %@",logg2);
    NSLog(@"*******This is the login view controller did update locationmethod of loginview controller.");
    NSLog(@"latitude is %f",[lat2 floatValue]);
    NSLog(@"longitude  is %f",[logg2 floatValue]);
    labellat.text = [NSString stringWithFormat: @"%f", loc.latitude];
    labellog.text= [NSString stringWithFormat: @"%f", loc.longitude];
    //NSLog(@"text of label is %@",labellat.text);
    //NSLog(@"text of label is %@",labellog.text);

    //lat=loc.latitude;
    //log=loc.longitude;
    //altitude.text = [NSString stringWithFormat: @"%f", newLocation.altitude];

    //    NSString *mapUrl = [NSString stringWithFormat: @"http://maps.google.com/maps?q=%f,%f", loc.latitude, loc.longitude];
    //    NSURL *url = [NSURL URLWithString:mapUrl];
    //    [[UIApplication sharedApplication] openURL:url];
}

- (IBAction)update {
    locmanager = [[CLLocationManager alloc] init];
    [locmanager setDelegate:self];
    [locmanager setDesiredAccuracy:kCLLocationAccuracyBest];
    NSLog(@"*********This is the location update method of login view controller.");
    [locmanager startUpdatingLocation];
}

Answer 1

基本内存管理：

lat2 = [NSString stringWithFormat: @"%f", loc.latitude];
logg2= [NSString stringWithFormat: @"%f", loc.longitude];

这些字符串在创建后几乎就被销毁（解除分配）。阅读内存管理指南。不要使用全局变量。如果必须，这应该可以解决你的字符串消失的问题：

[lat2 release];
[logg2 release];
lat2 = [[NSString stringWithFormat: @"%f", loc.latitude] retain]; // keep string alive until we release it
logg2= [[NSString stringWithFormat: @"%f", loc.longitude] retain];

哦，你还记得在Interface Builder中将插座连接到你的标签吗？

Answer 2

您可以使用

labellat.text = [NSString stringWithFormat: @"%@", lat2];
labellog.text= [NSString stringWithFormat: @"%@", logg2];

但我认为最好将纬度和经度值作为浮动本身存储在实例变量中，从而轻松访问它。如果您想在标签中显示它，请使用方法stringWithFormat:，就像您一样。

<强>更新

教程 Hello There: A CoreLocation Tutorial 可以为您提供帮助。

Answer 3

用此标签显示标签中的纬度和经度。

labellat.text = [NSString stringWithFormat: @"%.6f", loc.latitude];

labellog.text= [NSString stringWithFormat: @"%.6f", loc.longitude];

如果你想从任何其他地方调用这个值，请保留位置坐标以获取值，否则它可能是autorelase。

如何在iPhone中找到当前位置？

3 个答案: