初始化下载管理器

1、遍历正下载Plist的所有字典成模型数组

2、给所有下载模型赋值Task

3、计算所有模型的已下载大小

4、将模型数组赋值给下载管理器的临时数组

添加下载

1、判断当前url文件的下载状态（已下载、正下载、未下载）

2、

下载数据管理

1、临时下载信息路径
/Library/Caches/DownLoad/CacheList/自行车.mp4.plist

2、下载完成文件路径
/Library/Caches/DownLoad/LocalList/自行车.mp4

3、FinishedPlist.plist
[self.filelist addObject:_fileInfo];

4、临时.plist文件Path->下载信息Model

5、计算已下载文件的大小，方便继续断点下载

创建请求

• Get

//   NSURL
NSURL *url = [NSURL URLWithString:@""];
//   NSURLRequest
NSURLRequest *request = [NSURLRequest requestWithURL:url];
//   NSURLSession
NSURLSession *session = [NSURLSession sessionWithConfiguartion:[NSURLSessionConfiguration defaultSessionConfiguration]  delegate:self  delegateQueue:[[NSOpertationQueue alloc] init]];
//   NSURLSessionDataTask
NSURLSessionDataTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) {
     NSLog(@"%@", [NSJSONSerialazation JSONObjectWithData:data options:kNilOptions error:nil]);
}];
[task resume];

• Post

• Delegate

#pragma mark --------------------------------------- <NSURLSessionDataDelegate>
/**
 *  服务器开始响应
 */
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSHTTPURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
    // url标识符->请求模型
    JHDownloadInfo *info = [self downloadInfoForURL:dataTask.taskDescription];
    
    // 请求模型->准备开始
    [info didReceiveResponse:response];
    
    // 更新本地Plist表
    [self addToLocalPlist:info];
    
    // 回调开始下载
    if([self.downloadDelegate respondsToSelector:@selector(startDownload:)]) {
        [self.downloadDelegate startDownload:info];
    }
    
    // 继续
    completionHandler(NSURLSessionResponseAllow);
}


/**
 *  服务器发送数据
 */
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
    JHDownloadInfo *info = [self downloadInfoForURL:dataTask.taskDescription];
    
    [info didReceiveData:data];
    
    // 回调更新UI
    if([self.downloadDelegate respondsToSelector:@selector(updateCellProgress:)]) {
        [self.downloadDelegate updateCellProgress:info];
    }
}


/**
 *  服务器结束响应
 */
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    JHDownloadInfo *info = [self downloadInfoForURL:task.taskDescription];
    
    [info didCompleteWithError:error];
    
    [self resumeFirstWillResume];
    
    // 更新本地Plist表
    [self addToLocalPlist:info];
    
    // 回调下载完成
    if([self.downloadDelegate respondsToSelector:@selector(finishedDownload:)]) {
        [self.downloadDelegate finishedDownload:info];
    }
}

下载数据本地化

/**
 *  获取已下载文件
 */
-(NSArray*)getDownloadedFile
{
    NSString *downloadedPlistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadedInfo.plist"] prependCaches];
    
    NSArray *downloadedDictArray  = [NSArray arrayWithContentsOfFile:downloadedPlistPath];
    
    NSArray *downloadedModelArray = [JHDownloadInfo mj_objectArrayWithKeyValuesArray:downloadedDictArray];
   
    
    return downloadedModelArray;
}


/**
 *  获取正下载文件
 */
-(NSArray*)getDownloadingFile
{
    NSString *downloadingPlistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadingInfo.plist"] prependCaches];
    
    NSArray *downloadingDictArray  = [NSArray arrayWithContentsOfFile:downloadingPlistPath];
    
    NSArray *downloadingModelArray = [JHDownloadInfo mj_objectArrayWithKeyValuesArray:downloadingDictArray];
    
    
    return downloadingModelArray;
}

/**
 *  删除某一个文件
 */
-(void)delete:(JHDownloadInfo*)info{
    // 修改Plist
    [self deleteLocalPlist:info];
    
    // 删除文件
    if ([[NSFileManager defaultManager] fileExistsAtPath:info.file]) {
        [[NSFileManager defaultManager] removeItemAtPath:info.file error:nil];
    }
}

/**
 *  修改本地Plist
 */
- (void)deleteLocalPlist:(JHDownloadInfo*)fileinfo{
    NSString *plistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadingInfo.plist"] prependCaches];
    if (fileinfo.state == JHDownloadStateCompleted){
        plistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadedInfo.plist"] prependCaches];
    }
        
        
    NSMutableArray *downloadingArray = [[NSMutableArray alloc] initWithContentsOfFile:plistPath];
    [downloadingArray enumerateObjectsUsingBlock:^(NSDictionary *dict, NSUInteger idx, BOOL * _Nonnull stop) {
        NSString *url = [dict objectForKey:@"url"];
        if ([url isEqualToString:fileinfo.url]) [downloadingArray removeObject:dict];
    }];
    [downloadingArray writeToFile:plistPath atomically:YES];
}


/**
 *  添加本地Plist
 */
- (void)addToLocalPlist:(JHDownloadInfo*)fileinfo
{
    NSDictionary *fileDic = [fileinfo mj_keyValuesWithKeys:@[@"state",@"bytesWritten",@"totalBytesWritten",@"totalBytesExpectedToWrite",@"filename",@"file",@"url"]];
    
    
    NSString *plistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadingInfo.plist"] prependCaches];
    if (fileinfo.state == JHDownloadStateCompleted){
        // 移除正下载
        NSMutableArray *downloadingArray = [[NSMutableArray alloc] initWithContentsOfFile:plistPath];
        [downloadingArray enumerateObjectsUsingBlock:^(NSDictionary *dict, NSUInteger idx, BOOL * _Nonnull stop) {
            NSString *url = [dict objectForKey:@"url"];
            if ([url isEqualToString:fileinfo.url]) [downloadingArray removeObject:dict];
        }];
        [downloadingArray writeToFile:plistPath atomically:YES];
        
        // 添加新路径
        plistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadedInfo.plist"] prependCaches];
    }
    
    
    
    if([[NSFileManager defaultManager] fileExistsAtPath:plistPath]){
        NSMutableArray *array = [[NSMutableArray alloc] initWithContentsOfFile:plistPath];
        [array addObject:fileDic];
        BOOL success = [array writeToFile:plistPath atomically:YES];
        NSLog(@"%@",success?@"写入成功":@"写入失败");
    }else{
        NSMutableArray *array = [[NSMutableArray alloc] init];
        [array addObject:fileDic];
        BOOL success = [array writeToFile:plistPath atomically:YES];
        NSLog(@"%@",success?@"写入成功":@"写入失败");
    }
}

创建任务

• NSURLSession：NSURLSessionConfiguration、NSOperationQueue

- (NSURLSession *)session
{
    if (!_session) {
        // 配置
        NSURLSessionConfiguration *cfg = [NSURLSessionConfiguration defaultSessionConfiguration];
        // session
        self.session = [NSURLSession sessionWithConfiguration:cfg delegate:self delegateQueue:self.queue];
    }
    return _session;
}

- (NSOperationQueue *)queue
{
    if (!_queue) {
        self.queue = [[NSOperationQueue alloc] init];
        self.queue.maxConcurrentOperationCount = 1;
    }
    return _queue;
}

• NSURLSessionDataDelegate

1、开始响应

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSHTTPURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
    // 获得下载信息
    DownloadInfo *info = [self downloadInfoForURL:dataTask.taskDescription];
    
    // 处理响应
    [info didReceiveResponse:response];
    
    // 继续
    completionHandler(NSURLSessionResponseAllow);
}

2、正在响应

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{
    // 获得下载信息
    DownloadInfo *info = [self downloadInfoForURL:dataTask.taskDescription];
    
    // 处理数据
    [info didReceiveData:data];
}

3、结束响应

- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    // 获得下载信息
    DownloadInfo *info = [self downloadInfoForURL:task.taskDescription];
    
    // 处理结束
    [info didCompleteWithError:error];
    
    // 恢复等待下载的
    [self resumeFirstWillResume];
}

开始任务

• 获取下载模型

DownloadInfo *info = [self downloadInfoForURL:url];

#pragma mark - 获得下载信息
- (DownloadInfo *)downloadInfoForURL:(NSString *)url
{
    if (url == nil) return nil;
    
    DownloadInfo *info = [self.downloadInfoArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"url==%@", url]].firstObject;
    if (info == nil) {
        info = [[DownloadInfo alloc] init];
        info.url = url; // 设置url
        [self.downloadInfoArray addObject:info];
    }
    return info;
}

• 最大并发数Vs当前正下载

NSArray *downloadingDownloadInfoArray = [self.downloadInfoArray filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"state==%d", MJDownloadStateResumed]];
if (self.maxDownloadingCount && downloadingDownloadInfoArray.count == self.maxDownloadingCount) {
        // 等待下载
        [info willResume];
    } else {
        // 开始下载
        [info resume];
    }

• 等待下载

/** 任务 */
@property (strong, nonatomic) NSURLSessionDataTask *task;

• 开始下载

/** 任务 */
@property (strong, nonatomic) NSURLSessionDataTask *task;

[self.task resume];

初始化下载管理器

• 下载完成

/**
 *  服务器结束响应
 */
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
    JHDownloadInfo *info = [self downloadInfoForURL:task.taskDescription];
    
    [info didCompleteWithError:error];
    
    [self resumeFirstWillResume];
    
    if (!error) [self saveDownloadFile:info];
}

/**
 *  存储已下载文件
 */
- (void)saveDownloadFile:(JHDownloadInfo*)fileinfo
{
    NSString *downloadedPlistPath = [[NSString stringWithFormat:@"%@/%@", JHDownloadRootDir, @"DownloadedInfo.plist"] prependCaches];

    NSDictionary *fileDic = [fileinfo mj_keyValues];
    
    if([[NSFileManager defaultManager] fileExistsAtPath:downloadedPlistPath]){
        NSMutableArray *array = [[NSMutableArray alloc] initWithContentsOfFile:downloadedPlistPath];
        [array addObject:fileDic];
        BOOL success = [array writeToFile:downloadedPlistPath atomically:YES];
        NSLog(@"%@",success?@"写入成功":@"写入失败");
    }else{
        NSMutableArray *array = [[NSMutableArray alloc] init];
        [array addObject:fileDic];
        BOOL success = [array writeToFile:downloadedPlistPath atomically:YES];
        NSLog(@"%@",success?@"写入成功":@"写入失败");
    }
}

/**
 *  删除已下载的文件
 */
- (void)deleteFinishFile:(ZFFileModel *)selectFile
{
    [_finishedlist removeObject:selectFile];
    NSFileManager *fm = [NSFileManager defaultManager];
    NSString *path = FILE_PATH(selectFile.fileName);
    if ([fm fileExistsAtPath:path]) {
        [fm removeItemAtPath:path error:nil];
    }
    [self saveFinishedFile];
}

• 下载中

/**
 * 下载文件所有信息存储为plist
 */
- (void)saveDownloadFile:(ZFFileModel*)fileinfo
{
    NSData *imagedata = UIImagePNGRepresentation(fileinfo.fileimage);
    NSDictionary *filedic = [NSDictionary dictionaryWithObjectsAndKeys:fileinfo.fileName,@"filename",
                             fileinfo.fileURL,@"fileurl",
                             fileinfo.time,@"time",
                             fileinfo.fileSize,@"filesize",
                             fileinfo.fileReceivedSize,@"filerecievesize",
                             imagedata,@"fileimage",nil];
    
    NSString *plistPath = [fileinfo.tempPath stringByAppendingPathExtension:@"plist"];
    if (![filedic writeToFile:plistPath atomically:YES]) {
        NSLog(@"write plist fail");
    }
}

/*
 *  将本地的未下载完成的临时文件加载到正在下载列表里,但是不接着开始下载
 */
- (void)loadTempfiles
{
    NSFileManager *fileManager = [NSFileManager defaultManager];
    NSError *error;
    NSArray *filelist = [fileManager contentsOfDirectoryAtPath:TEMP_FOLDER error:&error];
    if(!error)
    {
        NSLog(@"%@",[error description]);
    }
    NSMutableArray *filearr = [[NSMutableArray alloc]init];
    for(NSString *file in filelist) {
        NSString *filetype = [file  pathExtension];
        if([filetype isEqualToString:@"plist"])
            [filearr addObject:[self getTempfile:TEMP_PATH(file)]];
    }
    
    NSArray* arr =  [self sortbyTime:(NSArray *)filearr];
    [_filelist addObjectsFromArray:arr];
    
    [self startLoad];
}