iOS 通过URL网络获取XML数据的两种方式

下面简单介绍如何通过url获取xml的两种方式。

第一种方式相对简单，使用NSData的构造函数dataWithContentsOfURL；不多解释，直接上代码咯。

    NSURL *url = [NSURL URLWithString:@"http://222.73.161.212/ispace2/servlet/com.lemon.xml.XmlAction"];         //A Boolean value that turns an indicator of network activity on or off.    [UIApplication sharedApplication].networkActivityIndicatorVisible = YES;        NSData *xmlData = [NSData dataWithContentsOfURL:url];        [UIApplication sharedApplication].networkActivityIndicatorVisible = NO;        NSString *xmlString = [[NSString alloc] initWithData:xmlData encoding:NSUTF8StringEncoding];        if (xmlData == nil) {        NSLog(@"File read failed!:%@", xmlString);    }    else {        NSLog(@"File read succeed!:%@",xmlString);    }

上面的  NSData *xmlData = [NSData dataWithContentsOfURL:url];就是获取xml的关键啦。

    注意：如果直接输出xmlData的话会是一对unicode，所以用UTF-8编码转换成是String进行输出就好啦。

第二种方式：通过NSURLConnection建立网络连接，并实现它的几个委托方法，从而获取数据。

代码如下，应该可以看懂的。

@implementation ViewController {    BOOL getXmlDone;  //是否停止获取xml数据的标志    NSMutableData *xmlData;  //存储获得的xml数据}//自定义的一个方法- (void) getXML {//获取xmlxmlData = [NSMutableData data];    //Clears the receiver’s cache, removing all stored cached URL responses.    //清除接收器的缓存，删除所有存储的高速缓存的URL的响应。    [[NSURLCache sharedURLCache] removeAllCachedResponses];NSURL *url = [NSURL URLWithString:@"http://222.73.161.212/ispace2/servlet/com.lemon.xml.XmlAction"];    NSURLRequest *theRequest = [NSURLRequest requestWithURL:url];    //create the connection with the request and start loading the data    NSURLConnection *urlConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];    [self performSelectorOnMainThread:@selector(downloadStarted) withObject:nil waitUntilDone:NO];    if (urlConnection != nil) {        do {            [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];        } while (!getXmlDone);    }}#pragma mark NSURLConnection Delegate methods- (NSCachedURLResponse *)connection:(NSURLConnection *)connection willCacheResponse:(NSCachedURLResponse *)cachedResponse {    return nil;}// Forward errors to the delegate.- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {    getXmlDone = YES;}// Called when a chunk of data has been downloaded.- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {    // Append the downloaded chunk of data.    [xmlData appendData:data];}- (void)connectionDidFinishLoading:(NSURLConnection *)connection {    [self performSelectorOnMainThread:@selector(downloadEnded) withObject:nil waitUntilDone:NO];    getXmlDone = YES;}- (void)downloadStarted {[UIApplication sharedApplication].networkActivityIndicatorVisible = YES;}- (void)downloadEnded {[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;}- (void)viewDidLoad{    [super viewDidLoad];// Do any additional setup after loading the view, typically from a nib.        [self getXML];    NSString *xmlString = [[NSString alloc] initWithData:xmlData encoding:NSUTF8StringEncoding];    NSLog(@"data: %@",xmlString);}- (void)didReceiveMemoryWarning{    [super didReceiveMemoryWarning];    // Dispose of any resources that can be recreated.}@end

小结一下，第一种简单，一次性获取所有的xml数据，第二种有点复杂，当然其灵活性也更好。

要验证获取的数据的准确性的话，就点击你的url吧！http://222.73.161.212/ispace2/servlet/com.lemon.xml.XmlAction

OK，下一篇文章将会介绍如何解析xml。come on!