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iPhone开发下载网络数据的几种方法总结

2013-01-18 12:14  三戒1993  阅读(119)  评论(0)  编辑  收藏  举报

  • view source
    print?
    01.NSString *urlAsString = @"http://www.jouhu.com/json/info.zip";－－－要下载的全路径名
    02.NSURL *url = [NSURL URLWithString:urlAsString];
    03.NSURLRequest *request = [NSURLRequest requestWithURL:url];
    04.NSError *error = nil;
    05. 
    06.NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];
    07./*下载的数据*/
    08.if (data!=nil) {
    09.NSLog(@"下载成功");
    10.if ([data writeToFile:@"/Users/sunningning/Desktop/activation.zip"atomically:YES]) {－－下载到目的路径名
    11.NSLog(@"保存成功！");
    12.}
    13.else
    14.{
    15.NSLog(@"保存失败！");
    16.}
    17.}
    18.else{
    19.NSLog(@"%@",error);
    20.}

    2 使用NSURLConnection的异步方法下载


    view source
    print?
    01.NSString *urlAsString = @"http://www.apple.com";
    02.NSURL *url = [NSURL URLWithString:urlAsString];
    03.NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];
    04.NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    05. 
    06.[NSURLConnection sendAsynchronousRequest:urlRequest queue:queue completionHandler:^(NSURLResponse *response,NSData *data, NSError *error)
    07.{
    08.if ([data length] >0 && error == nil){
    09.NSString *html = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    10.NSLog(@"HTML = %@", html); }
    11. 
    12.else if ([data length] == 0 && error == nil){
    13.NSLog(@"Nothing was downloaded.");
    14.}
    15. 
    16.else if (error != nil){
    17.NSLog(@"Error happened = %@", error); }
    18.}];

    3 使用NSURLConnection的异步+GCD的方法下载


    view source
    print?
    01.+ (void)performRequestWithUri:(NSString *)requestUri params:(NSDictionary *)params completionHandler:(void (^)(NSDictionary *, NSError *))completionBlock
    02.{
    03. 
    04.// Generate the URL
    05.NSString *requestUrl = [NSString stringWithFormat:@"http://the.api.com%@", requestUri];
    06. 
    07.// Create the connection
    08.NSURLRequest *request = [[NSURLRequest alloc] initWithURL:[NSURL URLWithString:requestUrl]];
    09. 
    10.// Make an NSOperationQueue
    11.NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    12.[queue setName:@"com.your.unique.queue.name"];
    13. 
    14.// Send an asyncronous request on the queue
    15.[NSURLConnection sendAsynchronousRequest:request queue:queue completionHandler:^(NSURLResponse *response, NSData *data, NSError *error) {
    16. 
    17.// If there was an error getting the data
    18.if (error) {
    19. 
    20.dispatch_async(dispatch_get_main_queue(), ^(void) {
    21.completionBlock(nil, error);
    22.});
    23.return;
    24.}
    25. 
    26.// Decode the data
    27.NSError *jsonError;
    28.NSDictionary *responseDict = [NSJSONSerialization JSONObjectWithData:data options:0 error:&jsonError];
    29. 
    30.// If there was an error decoding the JSON
    31.if (jsonError) {
    32. 
    33.dispatch_async(dispatch_get_main_queue(), ^(void) {
    34. 
    35.});
    36.return;
    37.}
    38. 
    39.// All looks fine, lets call the completion block with the response data
    40.dispatch_async(dispatch_get_main_queue(), ^(void) {
    41.completionBlock(responseDict, nil);
    42.});
    43.}];
    44.}

    具体调用方法：


    view source
    print?
    1.[SHAPIController performRequestWithUri:@"http://www.jouhu.com/json/info.php"params:nil completionHandler:^(NSDictionary *response, NSError *error) {
    2. 
    3.if (error) {
    4.NSLog(@"%@", error);
    5.}
    6. 
    7.NSLog(@"%@", response);
    8.}];

    返回的数据根据我们而定.
    4 实现delegate的方法实现异步


    view source
    print?
    01.NSURLConnection *conn= [[NSURLConnection alloc]
    02.initWithRequest:theRequest delegate:self];
    03.[conn start];
    04.if(conn)
    05.{
    06.NSLog(@"Connection Successful");
    07.}
    08.else
    09.{
    10.NSLog(@"Connection could not be made");
    11.}
    12.}

    view source
    print?
    01.- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)theResponse {
    02.self.response = theResponse;
    03.[data setLength:0]; // reset data
    04.}
    05. 
    06.- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)theData {
    07.[data appendData:theData]; // append incoming data
    08.}
    09. 
    10.- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
    11.[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    12.self.data = nil;
    13.if (handler) { [queue addOperationWithBlock:^{ handler(response, nil, error); }]; }
    14.}
    15. 
    16.- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    17.[UIApplication sharedApplication].networkActivityIndicatorVisible = NO;
    18.// TODO: Are we passing the arguments to the block correctly? Should we copy them?
    19.handleData(self.data);//处理数据，需要定义方法
    20.}

    我们自身的应用采用的是最后一种方法，对于很多图片更新的，可以采取第三种方法，第一种方法是同步数据下载，容易造成UI阻塞。需要注意。