[iOS]使用iOS8.0框架下URLSession对象实现断点下载功能

VideoDownLoadManager.h

//
//  VideoDownLoadManager.h
//  DowloadBreakPointDemo
//
//  Created by 郭晓敏 on 15/8/8.
//  Copyright (c) 2015年 com.jiaoxuebu.gxm. All rights reserved.
//

#import 
@class VideoModel;

@protocol VideoDownLoadManagerDelegate 

-(void)videoDidUpdatedProgressWithVideoModel:(VideoModel *)model;

@end

@interface VideoDownLoadManager : NSObject

@property(nonatomic, weak)iddelegate;

+(instancetype)sharedInstance;

@property(nonatomic, strong)NSOperationQueue *downLoadQueue;

//  用来保存创建的下载管理类，方面以后的对应管理
@property(nonatomic, strong)NSMutableDictionary *httpOperationDict;

@property(nonatomic, strong)NSMutableArray *downVideoArray;
#pragma mark 开始下载
-(void)startAVideoWithVideoModel:(VideoModel *)downLoadVideo;

#pragma mark 暂停下载
-(void)downloadPausewithModel:(VideoModel *)pauseModel;

#pragma mark 断点继续下载
-(void)downloadResumeWithModel:(VideoModel *)resumeModel;
@end

VideoDownLoadManager.m

//
//  VideoDownLoadManager.m
//  DowloadBreakPointDemo
//
//  Created by 郭晓敏 on 15/8/8.
//  Copyright (c) 2015年 com.jiaoxuebu.gxm. All rights reserved.
//

#import "VideoDownLoadManager.h"
#import "VideoModel.h"
#import "VideoDownLoadOperation.h"

@interface VideoDownLoadOperation ()

@end

static VideoDownLoadManager *manager;
@implementation VideoDownLoadManager
+(instancetype)sharedInstance
{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        if (manager == nil) {
            manager = [[VideoDownLoadManager alloc] init];
            manager.httpOperationDict = [NSMutableDictionary dictionary];
            manager.downVideoArray = [NSMutableArray array];

        }
    });

    return manager;
}
/*经过研究，AFN 的继续和暂停下载不是线程安全的，使用会经常出错*/
#pragma mark 开始下载
-(void)startAVideoWithVideoModel:(VideoModel *)downLoadVideo
{
    NSLog(@"........%@", CachesPath);
    if (!self.downLoadQueue) {
        self.downLoadQueue = [[NSOperationQueue alloc] init];
        self.downLoadQueue.maxConcurrentOperationCount = 3;
    }
    VideoDownLoadOperation *ope = [[VideoDownLoadOperation alloc] initWithDownLoadVideoModel:downLoadVideo];
    ope.updateBlock = ^(VideoModel *model){
        if (self.delegate && [self.delegate respondsToSelector:@selector(videoDidUpdatedProgressWithVideoModel:)]) {
            [self.delegate videoDidUpdatedProgressWithVideoModel:model];
        }
    };

    [self.httpOperationDict setObject:ope forKey:downLoadVideo.flv];
    [self.downLoadQueue addOperation:ope];
    [self.downVideoArray addObject:downLoadVideo];
    [[NSNotificationCenter defaultCenter] postNotificationName:k_newVideoDidStartDown object:nil];
}

#pragma mark 暂停下载
-(void)downloadPausewithModel:(VideoModel *)pauseModel
{

    
    VideoDownLoadOperation *ope = [self.httpOperationDict objectForKey:pauseModel.flv];
    if (!ope.isFinished) {
        [ope downLoadPause];
    }

}

#pragma mark 断点继续下载
-(void)downloadResumeWithModel:(VideoModel *)resumeModel
{
    VideoDownLoadOperation *ope = [self.httpOperationDict objectForKey:resumeModel.flv];
    if (!ope.isFinished) {
        [ope downLoadResume];
    }
}

@end

VideoDownLoadOperation.h

//
//  VideoDownLoadOperation.h
//  DowloadBreakPointDemo
//
//  Created by 郭晓敏 on 15/8/9.
//  Copyright (c) 2015年 com.jiaoxuebu.gxm. All rights reserved.
//

#import 
@class VideoModel;
typedef void(^VIDEODidUpateBlcok)(VideoModel *);

@interface VideoDownLoadOperation : NSOperation
-(instancetype)initWithDownLoadVideoModel:(VideoModel *)videoModel;

@property(nonatomic, copy)VIDEODidUpateBlcok updateBlock;
// 暂停
-(void)downLoadPause;
// 恢复
-(void)downLoadResume;
@end

VideoDownLoadOperation.m

//
//  VideoDownLoadOperation.m
//  DowloadBreakPointDemo
//
//  Created by 郭晓敏 on 15/8/9.
//  Copyright (c) 2015年 com.jiaoxuebu.gxm. All rights reserved.
//

#import "VideoDownLoadOperation.h"
#import "VideoModel.h"
@interface VideoDownLoadOperation ()
{
    // 用于判断一个任务是否正在下载
    BOOL _isDownLoading;

}
@property(nonatomic, strong)VideoModel *downLoadVideoModel;
// 定义 session
@property(nonatomic, strong)NSURLSession *currentSession;
// 用于可恢复的下载任务的数据
@property(nonatomic, strong)NSData *partialData;
// 可恢复的下载任务
@property(nonatomic, strong)NSURLSessionDownloadTask *task;
@end

@implementation VideoDownLoadOperation
-(instancetype)initWithDownLoadVideoModel:(VideoModel *)videoModel
{
    self = [super init];
    if (self) {
        self.downLoadVideoModel = videoModel;
    }
    return self;
}

-(void)main
{

    NSURLSessionConfiguration *configure = [NSURLSessionConfiguration defaultSessionConfiguration];

    self.currentSession = [NSURLSession sessionWithConfiguration:configure delegate:self delegateQueue:nil];
    self.currentSession.sessionDescription = self.downLoadVideoModel.flv;
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:self.downLoadVideoModel.flv]];
    self.task = [self.currentSession downloadTaskWithRequest:request];
    [self.task resume];
    _isDownLoading = YES;
    while (_isDownLoading) {
        [[NSRunLoop currentRunLoop] runUntilDate:[NSDate distantFuture]];
    }
    self.partialData = nil;
}
// 暂停
-(void)downLoadPause
{
    NSLog(@"暂停");
    [self.task suspend];
}
// 恢复
-(void)downLoadResume
{
    NSLog(@"恢复下载");
    [self.task resume];
}

#pragma mark delegate(task)
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{

    NSLog(@"path = %@", location.path);
    // 将临时文件剪切或者复制到 caches 文件夹
    NSFileManager *manager = [NSFileManager defaultManager];

    NSString *appendPath = [NSString stringWithFormat:@"/%@.mp4",self.downLoadVideoModel.title];
    NSString *file = [CachesPath stringByAppendingString:appendPath];

    [manager moveItemAtPath:location.path toPath:file error:nil];
    
    _isDownLoading = NO;

    // 下载完成发送通知
    dispatch_async(dispatch_get_main_queue(), ^{
        [[NSNotificationCenter defaultCenter] postNotificationName:k_videoDidDownedFinishedSuccess object:self.downLoadVideoModel];
        self.downLoadVideoModel.isDownFinished = YES;
    });

}

-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
    NSLog(@"-----%f", bytesWritten  * 1.0 / totalBytesExpectedToWrite);
    self.downLoadVideoModel.progressValue = totalBytesWritten / (double)totalBytesExpectedToWrite;
    dispatch_async(dispatch_get_main_queue(), ^{
        if (self.updateBlock) {
            self.updateBlock(self.downLoadVideoModel);
        }
    });
    
}

-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{
    NSLog(@"%.0f", fileOffset /(CGFloat) expectedTotalBytes);
}

@end