iOS开发之结合asp.net webservice实现文件上传下载

iOS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使用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。

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 = [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);
}

异步下载文件：

- ( 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 = [[NSMutableData alloc] init];
self.connectionData = 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: ];
}

- ( void ) viewDidUnload{
[super viewDidUnload];
[self.connection cancel];
self.connection = nil;
self.connectionData = nil;
}

从上面两段代码中可以看到同步与异步下载的区别，大部分时候我们使用异步下载文件。在asp.net webservice中可以将文件的地址返回到iOS系统，iOS系统在去请求下载该文件。

上传文件

我们先使用VB.Net写一个webservice方法，用于接收上传上来的文件数据，代码如下。

< class="brush:vbnet;gutter:false;"> <WebMethod(Description:="上传文件！")> _Public Function UploadFile() As XmlDocument Dim doc As XmlDocument = New XmlDocument() Try Dim postCollection As HttpFileCollection = Context.Request.Files Dim aFile As HttpPostedFile = postCollection("media") aFile.SaveAs(Server.MapPath(".") + "/" + Path.GetFileName(aFile.FileName)) doc.LoadXml("<xml>ok</xml>") Return doc Catch ex As Exception doc.LoadXml("<xml>fail</xml>") Return doc End Try End Function

文件上传接口

定义一个类PicOperation用于处理上传图片：

< class="brush:vbnet;gutter:false;">@interface PicOperation : NSOperation {UIImage *theImage;}@property (retain) UIImage *theImage;@end

< class="brush:objc;gutter:false;">//// PicOperation.m// DownLoading//// Created by skylin zhu on 11-7-30.// Copyright 2011年 mysoft. All rights reserved.//#import "PicOperation.h"#define NOTIFY_AND_LEAVE(X) {[self cleanup:X]; return;}#define DATA(X)[X dataUsingEncoding:NSUTF8StringEncoding]// Posting constants#define IMAGE_CONTENT @"Content-Disposition: form-data; name=\"%@\"; filename=\"image.jpg\"\r\nContent-Type: image/jpeg\r\n\r\n"#define STRING_CONTENT @"Content-Disposition: form-data; name=\"%@\"\r\n\r\n"#define MULTIPART @"multipart/form-data; boundary=------------0x0x0x0x0x0x0x0x"@implementation PicOperation@synthesize theImage;//创建postdata- (NSData*)generateFormDataFromPostDictionary:(NSDictionary*)dict{ id boundary = @"------------0x0x0x0x0x0x0x0x"; NSArray* keys = [dict allKeys]; NSMutableData* result = [NSMutableData data]; for (int i = 0; i < [keys count]; i++) { id value = [dict valueForKey: [keys objectAtIndex:i]]; [result appendData:[[NSString stringWithFormat:@"--%@\r\n", boundary] dataUsingEncoding:NSUTF8StringEncoding]];if ([value isKindOfClass:[NSData class]]) {// handle image dataNSString *formstring = [NSString stringWithFormat:IMAGE_CONTENT, [keys objectAtIndex:i]];[result appendData: DATA(formstring)];[result appendData:value];}else {// all non-image fields assumed to be stringsNSString *formstring = [NSString stringWithFormat:STRING_CONTENT, [keys objectAtIndex:i]];[result appendData: DATA(formstring)];[result appendData:DATA(value)];}NSString *formstring = @"\r\n"; [result appendData:DATA(formstring)]; }NSString *formstring =[NSString stringWithFormat:@"--%@--\r\n", boundary]; [result appendData:DATA(formstring)]; return result;}//上传图片- (NSString *) UpLoading{if (!self.theImage)NOTIFY_AND_LEAVE(@"Please set image before uploading."); NSMutableDictionary* post_dict = [[NSMutableDictionary alloc] init]; [post_dict setObject:@"Posted from iPhone" forKey:@"message"];[post_dict setObject:UIImageJPEGResentation(self.theImage, 0.75f) forKey:@"media"]; NSData *postData = [self generateFormDataFromPostDictionary:post_dict]; [post_dict release]; NSString *baseurl = @"http://10.5.23.121:7878/WorkflowService.asmx/UploadFile"; NSURL *url = [NSURL URLWithString:baseurl]; NSMutableURLRequest *urlRequest = [NSMutableURLRequest requestWithURL:url]; if (!urlRequest) NOTIFY_AND_LEAVE(@"Error creating the URL Request"); [urlRequest setHTTPMethod: @"POST"]; [urlRequest setValue:MULTIPART forHTTPHeaderField: @"Content-Type"]; [urlRequest setHTTPBody:postData]; // Submit & retrieve results NSError *error; NSURLResponse *response; NSLog(@"Contacting TwitPic...."); NSData* result = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error]; if (!result) { [self cleanup:[NSString stringWithFormat:@"Submission error: %@", [error localizedDescription]]]; return; } // Return results NSString *outstring = [[[NSString alloc] initWithData:result encoding:NSUTF8StringEncoding] autorelease]; return outstring; } @end

这里我主要定义了两个方法，一个是generateFormDataFromPostDictionary用于创建post form data，一个是UpLoading供调用的类上传图片，这个类需要一个UIimage的对象。

类定义好了，上传图片就非常方便了，看下面代码：

< class="brush:objc;gutter:false;"> PicOperation *pic = [[PicOperation alloc] init]; pic.theImage=[UIImage imageNamed:@"meinv4.jpg"];; NSString *result = [pic UpLoading]; NSLog(result);

总结：这篇文章讲述了如何在iOS中结合asp.net webservice实现文件的上传和下载功能。

原文链接： http://www.cnblogs.com/zhuqil/archive/2011/07/30/2122019.html