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！")> _
 ic 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。

文章转载自：http://blog.csdn.net/zhuqilin0/article/details/6646743