iPhone开发技巧总结----使用NSConnection下载数据

使用NSConnection下载数据 1.创建NSConnection对象，设置委托对象 NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:[self urlString]]]; [NSURLConnection connectionWithRequest:request delegate:self]; 2. NSURLConnection delegate委托方法 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response; - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error; - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data; - (void)connectionDidFinishLoading:(NSURLConnection *)connection; 3. 实现委托方法 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response { [self.receivedData setLength:0]; //通常在这里先清空接受数据的缓存 } - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data { [self.receivedData appendData:data]; //可能多次收到数据，把新的数据添加在现有数据最后 } - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error { // 错误处理 } - (void)connectionDidFinishLoading:(NSURLConnection *)connection { // disconnect [UIApplication sharedApplication].networkActivityIndicatorVisible = NO; NSString *returnString = [[NSString alloc] initWithData:self.receivedData encoding:NSUTF8StringEncoding]; NSLog(returnString); [self urlLoaded:[self urlString] data:self.receivedData]; firstTimeDownloaded = YES; } 三：使用NSXMLParser解析xml文件 1. 设置委托对象，开始解析 NSXMLParser *parser = [[NSXMLParser alloc] initWithData:data]; //或者也可以使用initWithContentsOfURL直接下载文件，但是有一个原因不这么做： // It's also possible to have NSXMLParser download the data, by passing it a URL, but this is not desirable // because it gives less control over the network, particularly in responding to connection errors. [parser setDelegate:self]; [parser parse]; 2. 常用的委托方法 - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict; - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName; - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string; - (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError; static NSString *feedURLString = @"http://www.yifeiyang.net/test/test.xml"; 3. 应用举例 - (void)parseXMLFileAtURL:(NSURL *)URL parseError:(NSError **)error { NSXMLParser *parser = [[NSXMLParser alloc] initWithContentsOfURL:URL]; [parser setDelegate:self]; [parser setShouldProcessNamespaces:NO]; [parser setShouldReportNamespacePrefixes:NO]; [parser setShouldResolveExternalEntities:NO]; [parser parse]; NSError *parseError = [parser parserError]; if (parseError && error) { *error = parseError; } [parser release]; } - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString*)qName attributes:(NSDictionary *)attributeDict{ // 元素开始句柄 if (qName) { elementName = qName; } if ([elementName isEqualToString:@"user"]) { // 输出属性值 NSLog(@"Name is %@ , Age is %@", [attributeDict objectForKey:@"name"], [attributeDict objectForKey:@"age"]); } } - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName { // 元素终了句柄 if (qName) { elementName = qName; } } - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { // 取得元素的text } NSError *parseError = nil; [self parseXMLFileAtURL:[NSURL URLWithString:feedURLString] parseError:&parseError];