iOS开发 -------- AFNetworking实现简单的断点下载

一 实现如下效果

---

 

二 实现代码

---

 //
 //  ViewController.m
 //  AFNetworking实现断点下载
 //
 //  Created by lovestarfish on 15/11/15.
 //  Copyright © 2015年 S&G. All rights reserved.
 //
 #define kURL @"http://v.hoto.cn/cc/45/869836.mp4?v=4"
 #import "ViewController.h"
 #import "AFNetworking.h"

 @interface ViewController ()

 @property (weak, nonatomic) IBOutlet UILabel *progressLabel;
 @property (weak, nonatomic) IBOutlet UIProgressView *progressView;
 @property (nonatomic,strong) AFHTTPRequestOperation *operation;

 - (IBAction)start:(UIButton *)sender;

 @end

 @implementation ViewController

 - (void)viewDidLoad {
     [super viewDidLoad];

     // 获取保存下载进度的缓存文件
     NSString *txtTempPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"mvTemp/mv.txt"];
     NSLog(@"%@",txtTempPath);
     NSFileManager *fileManager = [NSFileManager defaultManager];

     // 判断文件夹里面有没有之前的缓存文件
     if ([fileManager fileExistsAtPath:txtTempPath]) {
         // 有的话继续之前的下载进度下载
         self.progressView.progress = [[NSString stringWithContentsOfFile:txtTempPath encoding:NSUTF8StringEncoding error:nil] floatValue];
     } else {
         // 没有的话进度从0开始
         self.progressView.progress = ;
     }

     // 设置显示进度的label内容
     self.progressLabel.text = [NSString stringWithFormat:@"%.2f%%",self.progressView.progress * ];

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

 /**
  *  开始下载(下载的时候判断是否已经下载过该文件)
  */
 - (IBAction)start:(UIButton *)sender {
     // 创建文件管理对象
     NSFileManager *fileManager = [NSFileManager defaultManager];
     // 视频文件
     NSString *mp4Path = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches/mv/mv.mp4"];
     // 视频文件夹
     NSString *mvPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Library/Caches/mv"];
     //缓存文件夹
     NSString *mvTempPath = [NSTemporaryDirectory() stringByAppendingPathComponent:@"mvTemp"];

     // 如果存在mp4Path路径则说明已经下载该文件,此时提示用户是否需要重新下载
     if ([fileManager fileExistsAtPath:mp4Path]) {// 存在该文件
         UIAlertController *alertC = [UIAlertController alertControllerWithTitle:@"提示" message:@"文件已经存在,是否重新下载" preferredStyle:UIAlertControllerStyleAlert];
         // 确定行为
         UIAlertAction *doneAction = [UIAlertAction actionWithTitle:@"确定" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
             NSLog(@"点击了确定");
             // 重新下载,需要移除之前的视频文件夹和缓存文件夹
             [fileManager removeItemAtPath:mvPath error:nil];//视频文件夹
             [fileManager removeItemAtPath:mvTempPath error:nil];//缓存文件夹
             [self download:sender];
         }];

         // 取消行为
         UIAlertAction *cancelAction = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
             // 点击取消,直接return
             NSLog(@"点击了取消");
             return ;
         }];

         // 添加行为到控制器alertC
         [alertC addAction:doneAction];
         [alertC addAction:cancelAction];

         // 模态弹出提示框
         [self presentViewController:alertC animated:YES completion:nil];
     } else { // 不存在,直接下载
         [self download:sender];
     }
 }

 /**
  *  下载操作
  */
 - (void)download:(UIButton *)sender {
     NSFileManager *fileManager = [NSFileManager defaultManager];
     if ([sender.currentTitle isEqualToString:@"开始下载"]) {
         // 如果已经开始下载,将按钮标题置为"暂停下载"
         [sender setTitle:@"暂停下载" forState:UIControlStateNormal];

         // 下载的url
         NSURL *url = [NSURL URLWithString:kURL];
         // 获取cache文件夹
         NSString *cachePath = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) firstObject];

         // 在cache文件夹创建mv文件夹,用来存放下载成功地资料
         NSString *folderPath = [cachePath stringByAppendingPathComponent:@"mv"];
         // 在缓存文件夹里创建mvTemp文件夹用来临时存放下载信息
         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]) {// 如果不存在视频文件夹
             [fileManager createDirectoryAtPath:folderPath withIntermediateDirectories:YES attributes:nil error:nil];
         }
         if (![fileManager fileExistsAtPath:tempPath]) { // 如果不存在缓存文件夹
             [fileManager createDirectoryAtPath:tempPath withIntermediateDirectories:YES attributes:nil error:nil];
         }

         // 缓存路径(缓存当前下载的容量值)
         NSString *tempFilePath = [tempPath stringByAppendingPathComponent:@"mv.temp"];

         // 保存重启程序下载的进度(保存当前下载的进度值)
         NSString *txtFilePath = [tempPath stringByAppendingPathComponent:@"mv.txt"];

         // 文件保存路径
         NSString *mvFilePath = [folderPath stringByAppendingPathComponent:@"mv.mp4"];

         // 初始化下载字节数为0
         unsigned long long downloadedBytes = ;
         // 创建请求
         NSURLRequest *request = [NSURLRequest requestWithURL:url];
         if ([fileManager fileExistsAtPath:tempFilePath]) {//如果存在,说明有缓存文件
             // 计算缓存文件的大小
             downloadedBytes = [self fileSizeAtPath:tempFilePath];
             NSLog(@"%llu",downloadedBytes);
             // 创建可变请求
             NSMutableURLRequest *mutableRequest = [request mutableCopy];
             NSString *requestRange = [NSString stringWithFormat:@"bytes=%llu-",downloadedBytes];

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

         if (![fileManager fileExistsAtPath:mvFilePath]) {
             [[NSURLCache sharedURLCache] removeCachedResponseForRequest:request];
             self.operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
             [self.operation setOutputStream:[NSOutputStream outputStreamToFileAtPath:tempFilePath append:YES]];

             // 设置下载进度的block
             __block ViewController *vc = self;
             [self.operation setDownloadProgressBlock:^(NSUInteger bytesRead, long long totalBytesRead, long long totalBytesExpectedToRead) {
                 // 更新进度
                 vc.progressView.progress = ((float)totalBytesRead + downloadedBytes)/ (totalBytesExpectedToRead + downloadedBytes);
                 vc.progressLabel.text = [NSString stringWithFormat:@"%.2f%%",self.progressView.progress * ];
                 // 将进度写入缓存文件
                 NSString *progress = [NSString stringWithFormat:@"%.3f",((float)totalBytesRead + downloadedBytes) / ( totalBytesExpectedToRead + downloadedBytes)];
                 [progress writeToFile:txtFilePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
             }];

             // 下载完成时调用
             [self.operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation * _Nonnull operation, id  _Nonnull responseObject) {
                 //把下载完成的文件转移到保存的路径
                 [fileManager moveItemAtPath:tempFilePath toPath:mvFilePath error:nil];
                 //删除保存进度的txt文档
                 [fileManager removeItemAtPath:txtFilePath error:nil];
                 [sender setTitle:@"下载完成" forState:UIControlStateNormal];
             } failure:^(AFHTTPRequestOperation * _Nonnull operation, NSError * _Nonnull error) {

             }];

             // 开始操作
             [self.operation start];
         }
     } else {
         [sender setTitle:@"开始下载" forState:UIControlStateNormal];
         [self.operation cancel];
         self.operation = nil;
     }

 }

 /**
  *  计算缓存文件的大小
  *
  *  @param fileAbsolutePath 文件的绝对路径
  *
  *  @return 文件的大小
  */
 - (unsigned long long)fileSizeAtPath:(NSString *)fileAbsolutePath {
     signed long long fileSize = ;
     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