文件下载 ios

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。

    <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：

@interface PicOperation : NSOperation
{
    UIImage *theImage;
}
@property (retain) UIImage *theImage;
@end

 //
 //  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);