iphone http下载文件

(转 http://blog.csdn.net/rhljiayou/article/details/7616365)
头文件noteHttp.h

 1 #import <Foundation/Foundation.h>
 2 @interface NoteHttp : NSObject{
 3     //urlfbfh
 4     NSString *urlString;
 5     //下载的数据
 6     NSMutableData *dataNote;
 7 }
 8 @property(nonatomic,retain) NSString *urlString;
 9 @property(nonatomic,retain)NSMutableData *dataNote;
10 -(void)down;
11 @end

实现文件 noteHttp.m

 1 #import "NoteHttp.h"
 2 @implementation NoteHttp
 3 @synthesize urlString,dataNote,noteXml;
 4 - (id)init {
 5     self = [super init];
 6     if (!self) {
 7         [self release];
 8         return nil;
 9     }
10     urlString=[[NSString alloc]init];
11     dataNote=[[NSMutableData alloc]init];
12     return self;
13 }
14 -(void)down{
15     //http地址
16     urlString=@"http://192.168.67.3:8080/Todo/note.xml";
17     //转成NSURL，
18     NSURL *url=[NSURL URLWithString:urlString];
19     //负载请求
20     NSURLRequest *request=[[NSURLRequest alloc]initWithURL:url];
21     //异步请求，通过一个delegate来做数据的下载以及Request的接受等等消息，此处delegate:self，所以需要本类实现一些方法，并且定义receivedData做数据的接受
22     NSURLConnection *connection=[[NSURLConnection alloc]initWithRequest:request delegate:self];
23     [connection release];
24     [request release];
25     /*
26      但是异步模式下带来了一个新的问题，很多情况下，网络请求不在主线程，或者界面等待网络结果，不在主线程的时候，调用线程如果生命周期over，下面这些可能都没有调用到，导致得不到想要得效果，所以需要在NSURLConnection请求后面加点东西来阻塞
27      while(!finished) {
28      
29      [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDatedistantFuture]];
30      
31      }
32      */
33 }
34 //从网络上下载的数据,直到数据全部下载完成
35 -(void)connection:(NSURLConnection *)connection didReceiveData:(NSMutableData *)data{
36     [self.dataNote appendData:data];
37 }
38 //http交互正常，完成。
39 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
40 {
41     //沙盒路径
42     NSArray *paths= NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
43     NSString *documentsDirectory = [paths objectAtIndex:0];
44     NSString *path = [documentsDirectory stringByAppendingPathComponent:@"note.xml"];
45 
46     //当完成交互，也就是说数据下载完成时，就创建该文件
47     [[NSFileManager defaultManager]createFileAtPath:path contents:dataNote attributes:nil];
48 }
49 
50 //网络连接不成功，出现异常。
51 - (void)connection:(NSURLConnection *)connection 
52   didFailWithError:(NSError *)error
53 {
54     //如果出现异常，弹出对话框给出原因
55     UIAlertView *errorAlert = [[UIAlertView alloc]
56                                initWithTitle: [error localizedDescription]
57                                message: [error localizedFailureReason]
58                                delegate:nil
59                                cancelButtonTitle:@"OK"
60                                otherButtonTitles:nil];
61     [errorAlert show];
62     [errorAlert release];
63 
64 }
65 -(void)dealloc{
66     [urlString release];
67     [dataNote release];
68     [super dealloc];
69 }
70 @end