iOS文件下载

jopen 12年前

iOS</span>开发中会经常用到文件上传下载的功能，这篇文件将介绍一下如何结合asp.net webservice实现文件上传下载。 
首先，让我们看下文件下载。

这里我们下载cnblogs上的一个zip文件。使用NSURLRequest+NSURLConnection可以很方便的实现这个功能。在 asp.net webservice中可以将文件的地址返回到iOS系统，iOS系统再通过这个url去请求下载该文件。这里为了简单起见，直接将url写道代码里面了。我们可以使用两种方式去下载文件。

1、同步下载文件：

    NSString *urlAsString = @"http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip";                 NSURL    *url = [NSURL URLWithString:urlAsString];                 NSURLRequest *request = [NSURLRequest requestWithURL:url];                 NSError *error = nil;                 NSData   *data = http://www.cnblogs.com/zhwl/archive/2012/07/13/[NSURLConnection sendSynchronousRequest:request                                                        returningResponse:nil                                                                    error:&error];                 /* 下载的数据 */                 if (data != nil){                     NSLog(@"下载成功");                     if ([data writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {                         NSLog(@"保存成功.");                     }                     else                     {                         NSLog(@"保存失败.");                     }                 } else {                     NSLog(@"%@", error);                 }
2.异步下载
    DownLoadingViewController.h                //  DownLoadingViewController.h         //  DownLoading         //         //  Created by skylin zhu on 11-7-30.         //  Copyright 2011年 mysoft. All rights reserved.         //                 #import                 @interface DownLoadingViewController : UIViewController {             NSURLConnection *connection;              NSMutableData *connectionData;         }         @property (nonatomic,retain) NSURLConnection *connection;           @property (nonatomic,retain) NSMutableData *connectionData;         @end                 DownLoadingViewController.m                //  DownLoadingViewController.m         //  DownLoading         //         //  Created by skylin zhu on 11-7-30.         //  Copyright 2011年 mysoft. All rights reserved.         //                 #import "DownLoadingViewController.h"                 @implementation DownLoadingViewController         @synthesize connection,connectionData;         - (void)dealloc         {             [super dealloc];         }                 - (void)didReceiveMemoryWarning         {             // Releases the view if it doesn't have a superview.             [super didReceiveMemoryWarning];                         // Release any cached data, images, etc that aren't in use.         }                 #pragma mark - View lifecycle                         // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.         - (void)viewDidLoad         {             [super viewDidLoad];             //文件地址             NSString *urlAsString = @"http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip";             NSURL    *url = [NSURL URLWithString:urlAsString];             NSURLRequest *request = [NSURLRequest requestWithURL:url];             NSMutableData *data = http://www.cnblogs.com/zhwl/archive/2012/07/13/[[NSMutableData alloc] init];             self.connectionData = http://www.cnblogs.com/zhwl/archive/2012/07/13/data;             [data release];             NSURLConnection *newConnection = [[NSURLConnection alloc]                                               initWithRequest:request                                               delegate:self                                               startImmediately:YES];             self.connection = newConnection;             [newConnection release];             if (self.connection != nil){                NSLog(@"Successfully created the connection");             } else {                 NSLog(@"Could not create the connection");             }         }                                         - (void) connection:(NSURLConnection *)connection                     didFailWithError:(NSError *)error{             NSLog(@"An error happened");             NSLog(@"%@", error);         }         - (void) connection:(NSURLConnection *)connection                       didReceiveData:(NSData *)data{             NSLog(@"Received data");             [self.connectionData appendData:data];         }         - (void) connectionDidFinishLoading         :(NSURLConnection *)connection{             /* 下载的数据 */                         NSLog(@"下载成功");                 if ([self.connectionData writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {                     NSLog(@"保存成功.");                 }                 else                 {                     NSLog(@"保存失败.");                 }                       /* do something with the data here */         }         - (void) connection:(NSURLConnection *)connection                   didReceiveResponse:(NSURLResponse *)response{             [self.connectionData setLength:0];         }                 - (void) viewDidUnload{             [super viewDidUnload];             [self.connection cancel];             self.connection = nil;             self.connectionData = http://www.cnblogs.com/zhwl/archive/2012/07/13/nil;         }                 @end
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