iOS AFN进行断点下载-优快云博客

本文介绍了一个iOS应用中实现断点续传功能的具体方法。使用AFNetworking库进行网络请求，并通过缓存文件来实现断点续传。文章详细解释了如何创建缓存文件夹、读取缓存文件、计算已下载字节数以及更新下载进度。

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//
// ViewController.m
// Download

// Created by Congwang on 14/6/29.

//

#import "ViewController.h"
#import "AFNetworking.h"
@interface ViewController ()
@property ( retain , nonatomic ) IBOutlet UIProgressView *sliderView;
@property ( retain , nonatomic ) IBOutlet UILabel *progress;
@property ( nonatomic , retain ) AFHTTPRequestOperation   * operation;
@end

@implementation ViewController

- ( void )viewDidLoad {
    [ super viewDidLoad ];
     NSString * txtTempPath =[ NSTemporaryDirectory () stringByAppendingPathComponent : @"mvTemp/mv.txt" ];
NSFileManager *  fileManager =[ NSFileManager defaultManager ];
     if ([fileManager fileExistsAtPath :txtTempPath])
    {
         _sliderView . progress =  [[ NSString stringWithContentsOfFile :txtTempPath encoding : NSUTF8StringEncoding error : nil ] floatValue ];
    }

     else _sliderView . progress = 0 ;
     _progress . text = [ NSString stringWithFormat : @"%.2f%%" , _sliderView . progress * 100 ];
     // Do any additional setup after loading the view from its nib.

     NSLog ( @"%@" , NSHomeDirectory ());
}

- ( void )didReceiveMemoryWarning {
    [ super didReceiveMemoryWarning ];
     // Dispose of any resources that can be recreated.
}

- ( IBAction )start:( UIButton *)sender
{
    if ([sender. currentTitle isEqualToString : @" 开始下载 " ])
      {
          [sender setTitle : @" 暂停下载 " forState : UIControlStateNormal ];

     NSURL * url = [ NSURL URLWithString : @"http://www.demaxiya.com/app/index.php?m=play&vid=29996&quality=1" ];
     NSString * CachePath =[ NSSearchPathForDirectoriesInDomains ( NSCachesDirectory , NSUserDomainMask , YES ) firstObject ];
     NSFileManager *  fileManager =[ NSFileManager defaultManager ];
    NSLog ( @"%@" ,CachePath);
     NSString * folderPath = [CachePath stringByAppendingPathComponent : @"mv" ];
     NSString * tempPath =[ NSTemporaryDirectory () stringByAppendingPathComponent : @"mvTemp" ];
   // 判断缓存文件夹和视频存放文件夹是否存在 , 如果不存在 , 就创建一个文件夹
     if (![fileManager fileExistsAtPath :folderPath])
    {
        [fileManager createDirectoryAtPath :folderPath withIntermediateDirectories : YES attributes : nil error : nil ];
    }
//
     if (![fileManager fileExistsAtPath :tempPath])
    {
        [fileManager createDirectoryAtPath :tempPath withIntermediateDirectories : YES attributes : nil error : nil ];
    }

     NSString * tempFilePath = [tempPath stringByAppendingPathComponent : @"mv.temp" ]; // 缓存路径
     NSString * mvFilePath = [folderPath stringByAppendingPathComponent : @"mv.mp4" ]; // 文件保存路径
     NSString * txtFilePath = [tempPath stringByAppendingPathComponent : @"mv.txt" ]; // 保存重启程序下载的进度

        unsigned long long   downloadedBytes = 0 ;
     NSURLRequest * request = [ NSURLRequest    requestWithURL :url];

     if ([fileManager fileExistsAtPath :tempFilePath]) // 如果存在 , 说明有缓存文件
    {
        downloadedBytes = [ self fileSizeAtPath :tempFilePath]; // 计算缓存文件的大小
         NSMutableURLRequest *mutableURLRequest = [request mutableCopy ];
         NSString *requestRange = [ NSString stringWithFormat : @"bytes=%llu-" , downloadedBytes];

        [mutableURLRequest setValue :requestRange forHTTPHeaderField : @"Range" ];
        request = mutableURLRequest;
         NSLog ( @"============== 断点下载 " );
    }


     if (![fileManager   fileExistsAtPath :mvFilePath]) {

        [[ NSURLCache sharedURLCache ] removeCachedResponseForRequest :request];
        self . operation = [[ AFHTTPRequestOperation alloc ] initWithRequest :request];
        [ _operation setOutputStream :[ NSOutputStream outputStreamToFileAtPath : tempFilePath append : YES ]];

        [ _operation    setDownloadProgressBlock :^( NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {
             _sliderView . progress = (( float )totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes);
             _progress . text = [ NSString stringWithFormat : @"%.2f%%" , _sliderView . progress * 100 ];

             NSString * progress = [ NSString stringWithFormat : @"%.3f" ,(( float )totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes)];
            [progress writeToFile :txtFilePath atomically : YES encoding : NSUTF8StringEncoding error : nil ];
        }];

        [ _operation    setCompletionBlockWithSuccess :^( AFHTTPRequestOperation *operation, id responseObject)
         {

             [fileManager moveItemAtPath :tempFilePath toPath :mvFilePath error : nil ]; // 把下载完成的文件转移到保存的路径
              [fileManager removeItemAtPath :txtFilePath error : nil ]; // 删除保存进度的 txt 文档


         } failure :^( AFHTTPRequestOperation *operation, NSError *error)

         {


         }];
        [ _operation start ];
    } else
    {

    }
      }
       else
      {

          [sender setTitle : @" 开始下载 " forState : UIControlStateNormal ];
          [ self . operation cancel ];
            self . operation = nil ;

      }

}
// 计算缓存文件大小的方法
- ( unsigned long long )fileSizeAtPath:( NSString *)fileAbsolutePath {
     signed long long fileSize = 0 ;
     NSFileManager *fileManager = [ NSFileManager new ];
     if ([fileManager fileExistsAtPath :fileAbsolutePath]) {
         NSError *error = nil ;
         NSDictionary *fileDict = [fileManager attributesOfItemAtPath :fileAbsolutePath error :&error];
         if (!error && fileDict) {
            fileSize = [fileDict fileSize ];
        }
    }
     return fileSize;
}

@end