iOS开发——网络编程OC篇&（六）数据下载

浏览数：25 / 时间：2015年06月11日

文件下载

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。

小文件下载

 1 - (void)viewDidLoad
 2 {
 3     [super viewDidLoad];
 4     
 5     // 下载小文件的方式
 6     // 1.NSData dataWithContentsOfURL
 7     // 2.NSURLConnection
 8 }
 9 
10 // 1.NSData dataWithContentsOfURL
11 - (void)downloadFile
12 {
13     dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
14         // 其实这就是一个GET请求
15         NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/images/minion_01.png"];
16         NSData *data = [NSData dataWithContentsOfURL:url];
17         NSLog(@"%d", data.length);
18     });
19 }
20 
21 // 2.NSURLConnection
22 - (void)downloadFile2
23 {
24     NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/images/minion_01.png"];
25     NSURLRequest *request = [NSURLRequest requestWithURL:url];
26     [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
27         NSLog(@"%d", data.length);
28     }];
29 }

大文件下载

一：直接下载文件数据

 1 - (void)download
 2 {
 3     // 1.URL
 4     NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos.zip"];
 5     
 6     // 2.请求
 7     NSURLRequest *request = [NSURLRequest requestWithURL:url];
 8     
 9     // 3.下载(创建完conn对象后，会自动发起一个异步请求)
10     [NSURLConnection connectionWithRequest:request delegate:self];
11     
12 //    [[NSURLConnection alloc] initWithRequest:request delegate:self];
13 //    [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:YES];
14     
15 //    NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:request delegate:self startImmediately:NO];
16 //    [conn start];
17 }
18 
19 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
20 {
21     [self download];
22 }
23 
24 #pragma mark - NSURLConnectionDataDelegate代理方法
25 /**
26  *  请求失败时调用（请求超时、网络异常）
27  *
28  *  @param error      错误原因
29  */
30 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
31 {
32     NSLog(@"didFailWithError");
33 }
34 
35 /**
36  *  1.接收到服务器的响应就会调用
37  *
38  *  @param response   响应
39  */
40 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
41 {
42     NSLog(@"didReceiveResponse");
43     
44     // 初始化数据
45     self.fileData = [NSMutableData data];
46     
47     // 取出文件的总长度
48 //    NSHTTPURLResponse *resp = (NSHTTPURLResponse *)response;
49 //    long long fileLength = [resp.allHeaderFields[@"Content-Length"] longLongValue];
50     self.totalLength = response.expectedContentLength;
51 }
52 
53 /**
54  *  2.当接收到服务器返回的实体数据时调用（具体内容，这个方法可能会被调用多次）
55  *
56  *  @param data       这次返回的数据
57  */
58 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
59 {
60     // 拼接数据
61     [self.fileData appendData:data];
62     
63     // 设置进度值
64     // 0 ~ 1
65 //    self.progressView.progress = (double)self.fileData.length / self.totalLength;
66     self.circleView.progress = (double)self.fileData.length / self.totalLength;
67 }
68 
69 /**
70  *  3.加载完毕后调用（服务器的数据已经完全返回后）
71  */
72 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
73 {
74     NSLog(@"connectionDidFinishLoading");
75     
76     // 拼接文件路径
77     NSString *cache = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
78     NSString *file = [cache stringByAppendingPathComponent:@"videos.zip"];
79     
80     // 写到沙盒中
81     [self.fileData writeToFile:file atomically:YES];
82 }

二：下载数据的保存

 1 - (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
 2 {
 3     // 1.URL
 4     NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/music.zip"];
 5     
 6     // 2.请求
 7     NSURLRequest *request = [NSURLRequest requestWithURL:url];
 8     
 9     // 3.下载(创建完conn对象后，会自动发起一个异步请求)
10     [NSURLConnection connectionWithRequest:request delegate:self];
11 }
12 
13 #pragma mark - NSURLConnectionDataDelegate代理方法
14 /**
15  *  请求失败时调用（请求超时、网络异常）
16  *
17  *  @param error      错误原因
18  */
19 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
20 {
21     NSLog(@"didFailWithError");
22 }
23 
24 /**
25  *  1.接收到服务器的响应就会调用
26  *
27  *  @param response   响应
28  */
29 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
30 {
31     // 文件路径
32     NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
33     NSString *filepath = [caches stringByAppendingPathComponent:@"videos.zip"];
34     
35     // 创建一个空的文件 到 沙盒中
36     NSFileManager *mgr = [NSFileManager defaultManager];
37     [mgr createFileAtPath:filepath contents:nil attributes:nil];
38     
39     // 创建一个用来写数据的文件句柄
40     self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:filepath];
41     
42     // 获得文件的总大小
43     self.totalLength = response.expectedContentLength;
44 }
45 
46 /**
47  *  2.当接收到服务器返回的实体数据时调用（具体内容，这个方法可能会被调用多次）
48  *
49  *  @param data       这次返回的数据
50  */
51 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
52 {
53     // 移动到文件的最后面
54     [self.writeHandle seekToEndOfFile];
55     
56     // 将数据写入沙盒
57     [self.writeHandle writeData:data];
58     
59     // 累计文件的长度
60     self.currentLength += data.length;
61     
62     NSLog(@"下载进度：%f", (double)self.currentLength/ self.totalLength);
63     self.circleView.progress = (double)self.currentLength/ self.totalLength;
64 }
65 
66 /**
67  *  3.加载完毕后调用（服务器的数据已经完全返回后）
68  */
69 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
70 {
71     self.currentLength = 0;
72     self.totalLength = 0;
73     
74     // 关闭文件
75     [self.writeHandle closeFile];
76     self.writeHandle = nil;
77 }

断点下载：

 1 #pragma mark - NSURLConnectionDataDelegate代理方法
 2 /**
 3  *  请求失败时调用（请求超时、网络异常）
 4  *
 5  *  @param error      错误原因
 6  */
 7 - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
 8 {
 9     NSLog(@"didFailWithError");
10 }
11 
12 /**
13  *  1.接收到服务器的响应就会调用
14  *
15  *  @param response   响应
16  */
17 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
18 {
19     if (self.currentLength) return;
20     
21     // 文件路径
22     NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
23     NSString *filepath = [caches stringByAppendingPathComponent:@"videos.zip"];
24     
25     // 创建一个空的文件 到 沙盒中
26     NSFileManager *mgr = [NSFileManager defaultManager];
27     [mgr createFileAtPath:filepath contents:nil attributes:nil];
28     
29     // 创建一个用来写数据的文件句柄
30     self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:filepath];
31     
32     // 获得文件的总大小
33     self.totalLength = response.expectedContentLength;
34 }
35 
36 /**
37  *  2.当接收到服务器返回的实体数据时调用（具体内容，这个方法可能会被调用多次）
38  *
39  *  @param data       这次返回的数据
40  */
41 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
42 {
43     // 移动到文件的最后面
44     [self.writeHandle seekToEndOfFile];
45     
46     // 将数据写入沙盒
47     [self.writeHandle writeData:data];
48     
49     // 累计文件的长度
50     self.currentLength += data.length;
51     
52     self.circleView.progress = (double)self.currentLength/ self.totalLength;
53 }
54 
55 /**
56  *  3.加载完毕后调用（服务器的数据已经完全返回后）
57  */
58 - (void)connectionDidFinishLoading:(NSURLConnection *)connection
59 {
60     self.currentLength = 0;
61     self.totalLength = 0;
62     
63     // 关闭文件
64     [self.writeHandle closeFile];
65     self.writeHandle = nil;
66 }
67 
68 - (IBAction)download:(UIButton *)sender {
69     // 状态取反
70     sender.selected = !sender.isSelected;
71     
72     // 断点续传
73     // 断点下载
74     
75     if (sender.selected) { // 继续（开始）下载
76         // 1.URL
77         NSURL *url = [NSURL URLWithString:@"http://localhost:8080/MJServer/resources/videos.zip"];
78         
79         // 2.请求
80         NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
81         
82         // 设置请求头
83         NSString *range = [NSString stringWithFormat:@"bytes=%lld-", self.currentLength];
84         [request setValue:range forHTTPHeaderField:@"Range"];
85         
86         // 3.下载(创建完conn对象后，会自动发起一个异步请求)
87         self.conn = [NSURLConnection connectionWithRequest:request delegate:self];
88     } else { // 暂停
89         [self.conn cancel];
90         self.conn = nil;
91     }
92 }

iOS开发中文件下载可以使用同步和异步下载，但是一般开发中为了良好的用户交互，很少使用同步。

同步下载

 1 NSString *urlAsString = @"http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip";  
 2         NSURL    *url = [NSURL URLWithString:urlAsString];  
 3         NSURLRequest *request = [NSURLRequest requestWithURL:url];  
 4         NSError *error = nil;  
 5         NSData   *data = http://www.cnblogs.com/zhwl/archive/2012/07/13/[NSURLConnection sendSynchronousRequest:request  
 6                                                returningResponse:nil  
 7                                                            error:&error];  
 8         /* 下载的数据 */  
 9         if (data != nil){  
10             NSLog(@"下载成功");  
11             if ([data writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {  
12                 NSLog(@"保存成功.");  
13             }  
14             else  
15             {  
16                 NSLog(@"保存失败.");  
17             }  
18         } else {  
19             NSLog(@"%@", error);  
20         }

异步下载

  1 DownLoadingViewController.h 
  2    
  3 //  DownLoadingViewController.h  
  4 //  DownLoading  
  5 //  
  6 //  Created by skylin zhu on 11-7-30.  
  7 //  Copyright 2011年 mysoft. All rights reserved.  
  8 //  
  9    
 10 #import  
 11    
 12 @interface DownLoadingViewController : UIViewController {  
 13     NSURLConnection *connection;   
 14     NSMutableData *connectionData;  
 15 }  
 16 @property (nonatomic,retain) NSURLConnection *connection;    
 17 @property (nonatomic,retain) NSMutableData *connectionData;  
 18 @end  
 19    
 20 DownLoadingViewController.m 
 21    
 22 //  DownLoadingViewController.m  
 23 //  DownLoading  
 24 //  
 25 //  Created by skylin zhu on 11-7-30.  
 26 //  Copyright 2011年 mysoft. All rights reserved.  
 27 //  
 28    
 29 #import "DownLoadingViewController.h"  
 30    
 31 @implementation DownLoadingViewController  
 32 @synthesize connection,connectionData;  
 33 - (void)dealloc  
 34 {  
 35     [super dealloc];  
 36 }  
 37    
 38 - (void)didReceiveMemoryWarning  
 39 {  
 40     // Releases the view if it doesn‘t have a superview.  
 41     [super didReceiveMemoryWarning];  
 42        
 43     // Release any cached data, images, etc that aren‘t in use.  
 44 }  
 45    
 46 #pragma mark - View lifecycle  
 47    
 48    
 49 // Implement viewDidLoad to do additional setup after loading the view, typically from a nib.  
 50 - (void)viewDidLoad  
 51 {  
 52     [super viewDidLoad];  
 53     //文件地址  
 54     NSString *urlAsString = @"http://files.cnblogs.com/zhuqil/UIWebViewDemo.zip";  
 55     NSURL    *url = [NSURL URLWithString:urlAsString];  
 56     NSURLRequest *request = [NSURLRequest requestWithURL:url];  
 57     NSMutableData *data = http://www.cnblogs.com/zhwl/archive/2012/07/13/[[NSMutableData alloc] init];  
 58     self.connectionData = http://www.cnblogs.com/zhwl/archive/2012/07/13/data;  
 59     [data release];  
 60     NSURLConnection *newConnection = [[NSURLConnection alloc]  
 61                                       initWithRequest:request  
 62                                       delegate:self  
 63                                       startImmediately:YES];  
 64     self.connection = newConnection;  
 65     [newConnection release];  
 66     if (self.connection != nil){  
 67        NSLog(@"Successfully created the connection");  
 68     } else {  
 69         NSLog(@"Could not create the connection");  
 70     }  
 71 }  
 72    
 73    
 74    
 75    
 76 - (void) connection:(NSURLConnection *)connection  
 77             didFailWithError:(NSError *)error{  
 78     NSLog(@"An error happened");  
 79     NSLog(@"%@", error);  
 80 }  
 81 - (void) connection:(NSURLConnection *)connection  
 82               didReceiveData:(NSData *)data{  
 83     NSLog(@"Received data");  
 84     [self.connectionData appendData:data];  
 85 }  
 86 - (void) connectionDidFinishLoading  
 87 :(NSURLConnection *)connection{  
 88     /* 下载的数据 */  
 89    
 90         NSLog(@"下载成功");  
 91         if ([self.connectionData writeToFile:@"UIWebViewDemo.zip" atomically:YES]) {  
 92             NSLog(@"保存成功.");  
 93         }  
 94         else  
 95         {  
 96             NSLog(@"保存失败.");  
 97         }  
 98      
 99     /* do something with the data here */  
100 }  
101 - (void) connection:(NSURLConnection *)connection  
102           didReceiveResponse:(NSURLResponse *)response{  
103     [self.connectionData setLength:0];  
104 }  
105    
106 - (void) viewDidUnload{  
107     [super viewDidUnload];  
108     [self.connection cancel];  
109     self.connection = nil;  
110     self.connectionData = http://www.cnblogs.com/zhwl/archive/2012/07/13/nil;  
111 }  
112    
113 @end