ios kmlviewer 加载远程 url 而不是本地文件

Question

我使用的是 Apple 的 kmlviewer 示例，但它从本地目录中获取 kml 文件。我想要做的是使用 url 远程调用该文件。

这是来自 Apple 的原始代码：

NSString *path = [[NSBundle mainBundle] pathForResource:@"KML_Sample" ofType:@"kml"];
NSURL *url = [NSURL fileURLWithPath:path];
kmlParser = [[KMLParser alloc] initWithURL:url];
[kmlParser parseKML];

如何调用位于 url 中的远程文件为：http://www.domain.com/route.kml？

最好的问候。

Answer 1

我在 KMLParser 中添加了一个 Initializer 来使用 NSData：

在 KMLParser.h 文件中，添加：

-(id) initWithData: (NSData *) data;

在 KMLParser.m 文件中添加：

-(id) initWithData: (NSData *)data
{
    if (self = [super init]) {
        _styles = [[NSMutableDictionary alloc] init];
        _placemarks = [[NSMutableArray alloc] init];
        _xmlParser = [[NSXMLParser alloc] initWithData:data];

        [_xmlParser setDelegate:self];
    }
    return self;
}

Answer 2

MapViewController.h：

    .....
    NSMutableData   *webData;
    KMLParser       *kml;
    .....
    @property (nonatomic, retain) NSMutableData   *webData;

MapViewController.m：

- (IBAction)showKmlData:(id)sender  //Let's say you want to download kml data with a button tap, you create a method for that (you may not act like this, but the content is the same):
{
    NSURL *path = [NSURL URLWithString:@"http://www.domain.com/route.kml"];
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:path];
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

    [connection release];
    [request release];
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
   self.webData =[NSMutableData data];
}


-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{   
    [webData appendData:data];
}

-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *fileName = [[[NSURL URLWithString:kmlStr] path] lastPathComponent];
    //NSString *fileName = @"route.kml"; 
    NSArray *pathArr = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *folder = [pathArr objectAtIndex:0];

    NSString *filePath = [folder stringByAppendingPathComponent:fileName];
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];  
    NSError *writeError = nil;

    [webData writeToURL: fileURL options:0 error:&writeError];

    if( writeError) {
        NSLog(@" Error in writing file %@' : \n %@ ", filePath , writeError );
        return;
    }

    kml = [[KMLParser parseKMLAtPath:filePath] retain];

    NSArray *annotations = [kml points];

    if ([[mapview overlays] count] == 0) {
        [mapview addAnnotations:annotations];

        NSArray *overlays = [kml overlays];
        [mapview addOverlays:overlays];
        MKMapRect flyTo = MKMapRectNull;

        for (id <MKOverlay> overlay in overlays) {
            if (MKMapRectIsNull(flyTo)) {
                flyTo = [overlay boundingMapRect];
            } else {
                flyTo = MKMapRectUnion(flyTo, [overlay boundingMapRect]);
            }
        }

        for (id <MKAnnotation> annotation in annotations) {
            MKMapPoint annotationPoint = MKMapPointForCoordinate(annotation.coordinate);
            MKMapRect pointRect = MKMapRectMake(annotationPoint.x, annotationPoint.y, 0, 0);
            if (MKMapRectIsNull(flyTo)) {
                flyTo = pointRect;
            } else {
                flyTo = MKMapRectUnion(flyTo, pointRect);
            }
        }

        mapview.visibleMapRect = flyTo;
    }

    [mapview addAnnotations:annotations];
    NSArray *overlays = [kml overlays];
    [mapview addOverlays:overlays];
}

-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"Error!" message:@"An error has occured." delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    [alert show];
    [alert release];
}

Answer 3

我会下载文件并将其保存在本地文档或临时目录中。基本步骤是：

• 用你想要的 URL 创建一个 NSURLRequest
• 使用该 NSURLRequest 创建一个 NSURLConnection
• 创建一个 NSMutableData 成员变量来存储从 NSURLConnection 接收到的数据。
• 实现 NSURLConnection 委托的方法：
  • connection:didReceiveResponse（确保成功，即 http 200）
  • connection:didReceiveData（将接收到的数据附加到您的 NSMutableData 变量中）
  • connection:didFailWithError（处理错误）
  • connectionDidFinishLoading（现在收到所有数据，将其写入本地文件）

请参阅 Apple 提供的这个非常有用的示例项目，其中展示了如何按照我上面概述的步骤下载文件并将其保存在本地： http://developer.apple.com/library/ios/#samplecode/URLCache/Introduction/Intro.html

这里的 Apple 文档中也有一个很好的分步指南： https://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/URLLoadingSystem/Tasks/UsingNSURLConnection.html

然后，一旦您在本地拥有文件，使用 KMLParser 使用指向您将文件保存到的任何位置的 URL 打开将是微不足道的。

Answer 4

没有NSURLRequest 和NSURLConnection 很简单：

NSURL *url = [NSURL URLWithString:@"http://www.domain.com/route.kml"];
kmlParser = [[KMLParser parseKMLAsURL:url] retain];

NSArray *overlays = [kmlParser overlays];
[mapView addOverlays:overlays];

等等。用于注释。

至于parseKMLAtURL，它在Apple SDK的KMLViewer的另一个版本（1.1）中实现为：

+ (KMLParser)parseKMLAtURL:(NSURL *)url
{
    NSXMLParser *xml = [[NSXMLParser alloc] initWithContentsOfURL:url];
    KMLParser *parser = [[KMLParser alloc] init];
    [xmlParser setDelegate:parser];
    [xml parse];
    [parser _assignStyles];
    return [parser autorelease];
}