【网络】iOS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:0];
}

- (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

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);

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。

顶

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