iOS AFN进行断点下载

//
//  ViewController.m
//  Download

//

//  Created by Congwang on 14/6/29.

//  Copyright (c) 2014年 Congwang. All rights reserved.

//

#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 =  [[NSStringstringWithContentsOfFile:txtTempPathencoding:NSUTF8StringEncoding error:nil] floatValue];
    }
   
    else _sliderView.progress = 0;
    _progress.text = [NSStringstringWithFormat:@"%.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 = [NSURLURLWithString:@"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:folderPathwithIntermediateDirectories:YES attributes:nil error:nil];
    }
//
    if (![fileManager fileExistsAtPath:tempPath])
    {
        [fileManager createDirectoryAtPath:tempPathwithIntermediateDirectories: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 = [requestmutableCopy];
        NSString *requestRange = [NSStringstringWithFormat:@"bytes=%llu-", downloadedBytes];
       
        [mutableURLRequest setValue:requestRangeforHTTPHeaderField:@"Range"];
        request = mutableURLRequest;
        NSLog(@"==============断点下载");
    }

   
    if (![fileManager  fileExistsAtPath:mvFilePath]) {
       
        [[NSURLCache sharedURLCache] removeCachedResponseForRequest:request];
       self.operation= [[AFHTTPRequestOperation alloc]initWithRequest:request];
        [_operation setOutputStream:[NSOutputStreamoutputStreamToFileAtPath: tempFilePath append:YES]];
     
        [_operation  setDownloadProgressBlock:^(NSUIntegerbytesRead, long long totalBytesRead, long longtotalBytesExpectedToRead) {
            _sliderView.progress = ((float)totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes);
            _progress.text = [NSStringstringWithFormat:@"%.2f%%",_sliderView.progress *100];
         
            NSString * progress = [NSStringstringWithFormat:@"%.3f",((float)totalBytesRead + downloadedBytes) / (totalBytesExpectedToRead + downloadedBytes)];
            [progress writeToFile:txtFilePath atomically:YESencoding:NSUTF8StringEncoding error:nil];
        }];
       
        [_operation  setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
         {
            
             [fileManager moveItemAtPath:tempFilePathtoPath:mvFilePath error:nil];//把下载完成的文件转移到保存的路径
              [fileManager removeItemAtPath:txtFilePatherror: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 = [fileManagerattributesOfItemAtPath:fileAbsolutePath error:&error];
        if (!error && fileDict) {
            fileSize = [fileDict fileSize];
        }
    }
    return fileSize;
}

@end