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 = [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、异步下载文件：DownLoadingViewController.h

// // DownLoadingViewController.h // DownLoading // // Created by skylin zhu on 11-7-30. // Copyright 2011年 mysoft. All rights reserved. // #import <UIKit/UIKit.h> @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 = [[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:0]; } - (void) viewDidUnload{ [super viewDidUnload]; [self.connection cancel]; self.connection = nil; self.connectionData = nil; } @end

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。

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，我们可以从Request.Files中获取上传上来的文件数据。代码如下。

<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

定义一个类PicOperation用于处理上传图片：PicOperation.h

// // PicOperation.h // DownLoading // // Created by skylin zhu on 11-7-30. // Copyright 2011年 mysoft. All rights reserved. // #import <Foundation/Foundation.h> @interface PicOperation : NSOperation { UIImage *theImage; } @property (retain) UIImage *theImage; @end

PicOperation.m：

// // 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 data NSString *formstring = [NSString stringWithFormat:IMAGE_CONTENT, [keys objectAtIndex:i]]; [result appendData: DATA(formstring)]; [result appendData:value]; } else { // all non-image fields assumed to be strings NSString *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:UIImageJPEGRepresentation(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：

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。