多个注释未显示（Xcode mapview）答案

【问题标题】：Multiple annotations not showing (Xcode mapview)多个注释未显示（Xcode mapview）
【发布时间】：2012-01-19 16:59:15
【问题描述】：

[super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.

NSArray *name = [NSArray arrayWithObjects:@"Marina Bay Sands", @"Sentosa", @"Singapore Polytechnic",nil];
NSArray *description = [NSArray arrayWithObjects:@"Got casino!!", @"Got Universal Studio Singapore!!", @"Best polytechnic in Singapore!",nil];    

self.mapAnnotations = [[NSMutableArray alloc] initWithCapacity:3];

//Set coordinates for pin
CLLocationCoordinate2D location;
location.latitude = (double)1.2822463547298561;
location.longitude = (double) 103.85830879211426;
MapPin *mapPin = [[MapPin alloc] init];
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:0]];
[mapPin setDescription:[description objectAtIndex:0]];
[self.mapAnnotations addObject:mapPin];

location.latitude = (double) 1.249404;
location.longitude = (double) 103.830321;
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:1]];
[mapPin setDescription:[description objectAtIndex:1]];
[self.mapAnnotations addObject:mapPin];

location.latitude = (double) 1.309976;
location.longitude = (double) 103.775921;
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:2]];
[mapPin setDescription:[description objectAtIndex:2]];
[self.mapAnnotations addObject:mapPin];

[self.mapView addAnnotations:self.mapAnnotations];

self.mapView.mapType = MKMapTypeStandard;
[self location];
mapView.showsUserLocation = YES;

嗨，Xcode 编程相当新，这是我在 viewDidLoad 中的代码。我正在尝试显示多个注释，这只是为了尝试。但是从这段代码中，我只能显示 1 个注释，它是我添加到 mapAnnotations 数组中的最后一个对象。

我可以让它工作的唯一方法是初始化 mapPin1 和 mapPin2，而不是全部使用 mapPin我要创建的两个注释。但是这种方式似乎效率很低（如果我错了，请纠正我）而且，我有数百个数据要添加。不可能对它们进行硬编码。

有人可以帮我解决这个问题吗？

谢谢你=)

【问题讨论】：

标签： ios xcode ipad annotations android-mapview

【解决方案1】：

我已将 cmets 添加到您的代码中，以显示真正正在发生的事情。

[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.

NSArray *name = [NSArray arrayWithObjects:@"Marina Bay Sands", @"Sentosa", @"Singapore 
    Polytechnic",nil];
NSArray *description = [NSArray arrayWithObjects:@"Got casino!!", @"Got Universal Studio 
    Singapore!!", @"Best polytechnic in Singapore!",nil];    

self.mapAnnotations = [[NSMutableArray alloc] initWithCapacity:3];

//here you create the properties of the pin the first time
CLLocationCoordinate2D location;
location.latitude = (double)1.2822463547298561;
location.longitude = (double) 103.85830879211426;

//here you create the pin
MapPin *mapPin = [[MapPin alloc] init];

//now you set its properties
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:0]];
[mapPin setDescription:[description objectAtIndex:0]];
//now you add it to the array
[self.mapAnnotations addObject:mapPin];

//now you are changing the properties of `mapPin`
location.latitude = (double) 1.249404;
location.longitude = (double) 103.830321;
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:1]];
[mapPin setDescription:[description objectAtIndex:1]];

//the problem with adding mapPin again here is that you are adding
//the same object again, just with different properties, so
//your array still only has one object in it, `mapPin`, but with its updated properties
[self.mapAnnotations addObject:mapPin];

//you change the properties again here
location.latitude = (double) 1.309976;
location.longitude = (double) 103.775921;
[mapPin setCoordinate:location];
[mapPin setName: [name objectAtIndex:2]];
[mapPin setDescription:[description objectAtIndex:2]];

//and the same phenomenon I previously described happens again here
[self.mapAnnotations addObject:mapPin];

[self.mapView addAnnotations:self.mapAnnotations];

self.mapView.mapType = MKMapTypeStandard;
[self location];
mapView.showsUserLocation = YES;

如果您不想在每次将它们添加到数组时创建新的 mapPins，请在每次将图钉添加到数组时尝试此操作：

代替

[self.mapAnnotations addObject:mapPin];

试试

[self.mapAnnotations addObject:[[mapPin copy] autorelease]];

这将添加您修改后的 mapPin 的副本，而不是指向原来所在的内存空间。

【讨论】：

很高兴我能帮上忙。如果我的回答解决了你的问题，请注明！

【解决方案2】：

您正在创建一个mapPin 并重复添加相同的对象。您需要为要添加到地图的每个注释 alloc/init 一个新的注释对象。

【讨论】：

【解决方案3】：

找线索试试

int howManyAreThere = [self.mapAnnotations count];

在你的 3 添加并断点它以查看实际发生的情况。

虽然 NSMutableArray 处理重复项，但它不会复制您传递给它的对象。 比这更聪明。

【讨论】：

【解决方案4】：

获取数组中的所有 lat long 并使用以下代码

for (int i = 0; i < [arrListing count]; i++) {


            List *obj = [arrList objectAtIndex:i];
            NSLog(@"Title %@  long:%@  Lat:%@",obj.Title,obj.log,obj.lat);

            CLLocationCoordinate2D annotationCoord;

            annotationCoord.latitude = [obj.lat floatValue];
            annotationCoord.longitude = [obj.log floatValue];

            MKPointAnnotation *annotationPoint = [[MKPointAnnotation alloc] init];
            annotationPoint.coordinate = annotationCoord;
            annotationPoint.title = obj.Title;
            annotationPoint.subtitle = obj.log;
            [mapView addAnnotation:annotationPoint];
        }

【讨论】：