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#import <Foundation/Foundation.h> @class YGFileDownloader; @protocol YGFileDownloaderDelegate <NSObject> -(void)fileDownloader:(YGFileDownloader *)downloader downloadSize:(unsigned long long)downloadSize totalSize:(unsigned long long)totalSize; -(void)fileDownloaderDidFinishLoad; -(void)fileDownloaderFailWithError:(NSError *)error; @end @interface YGFileDownloader : NSObject @property (nonatomic,weak) id<YGFileDownloaderDelegate> delegate; +(instancetype)sharedInstance; -(void)start:(NSString *)urlStr; -(void)stop; @end

#import "YGFileDownloader.h"

#import "NSString+util.h" @interface YGFileDownloader () <NSURLConnectionDataDelegate> @property (nonatomic,strong) NSURLConnection *connection; @property (nonatomic,copy) NSString *downloadDocPath;//这个路径标识我们下载的文件所存储的那个目录，他是写死的，每次下载东西都能放在目录下面 @property (nonatomic,strong) NSFileHandle *fileHandle; @property (nonatomic) unsigned long long downloadFileSize;//当前下载了多少（字节） @property (nonatomic) unsigned long long totalFileSize;//文件总大小 @end @implementation YGFileDownloader -(NSString *)downloadDocPath{     if (_downloadDocPath==nil) {         //找到沙盒的Document目录         NSString *documentPath=[NSSearchPathForDirectoriesInDomains(NSDocumentationDirectory, NSUserDomainMask, YES) objectAtIndex:0];         //上面这句代码和 [NSHomeDirectory()stringByAppendingPathComponent:@"Documents"];一样         NSString *downloadPath=[documentPath stringByAppendingPathComponent:@"YGFileDownload"];         BOOL isSuccess=[[NSFileManager defaultManager] createDirectoryAtPath:downloadPath withIntermediateDirectories:YES attributes:nil error:nil];         if (isSuccess) {             NSLog(@"创建文件夹成功");         }         _downloadDocPath=downloadPath;     }     return _downloadDocPath; } +(instancetype)sharedInstance{//创建单例对象     static YGFileDownloader *downloader=nil;     static dispatch_once_t onceToken;     dispatch_once(&onceToken,^{//大括号里的代码只会执行一次         downloader=[[YGFileDownloader alloc] init];     });     return downloader; } -(void)start:(NSString *)urlStr{     NSString *fullPath=[self prepareStart:urlStr];     //获取fullPath标识的文件的大小     _downloadFileSize=[self readDownloadFileSize:fullPath];          NSMutableURLRequest *request=[[NSMutableURLRequest alloc] initWithURL:[NSURL URLWithString:urlStr]];     [request addValue:[NSString stringWithFormat:@"bytes=%llu-",_downloadFileSize] forHTTPHeaderField:@"Range"];//告诉服务器请求_downloadFileSize以后的字节     self.connection=[[NSURLConnection alloc] initWithRequest:request delegate:self];      } -(NSString *)prepareStart:(NSString *)urlStr{//确保urlStr所对应的沙盒的位置上有文件     NSString *fileName=urlStr.md5;//把url所对应的MD5值作为文件名          //fullPath代表这个文件具体的位置（路径）     NSString *fullPath=[self.downloadDocPath stringByAppendingString:fileName];          //如果指定的这个路径下面不存在这个文件，我们就把他创建出来     BOOL fileExists=[[NSFileManager defaultManager] fileExistsAtPath:fullPath];     if (!fileExists) {         [[NSFileManager defaultManager] createFileAtPath:fullPath contents:nil attributes:nil];     }          //打开这个文件准备往里面写数据     self.fileHandle=[NSFileHandle fileHandleForWritingAtPath:fullPath];          return fullPath;     //这个函数的功能是在准备下载文件之前做一些准备工作：1.确保文件存在，2.打开文件准备往里面写数据，3.获取这个文件的确切路径，因为我们在往这个路径所标识的这个文件中写数据（我们下载的数据） } -(unsigned long long)readDownloadFileSize:(NSString *)filePath{//读取filePath文件的文件大小     NSDictionary *fileInfo=[[NSFileManager defaultManager] attributesOfItemAtPath:filePath error:nil];     return [fileInfo fileSize]; } -(void)stop{     [_connection cancel],_connection=nil;     [_fileHandle closeFile],_fileHandle=nil; } #pragma mark - <NSURLConnectionDataDelegate> -(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{     _totalFileSize=_downloadFileSize+response.expectedContentLength; } -(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{     if ([self.delegate conformsToProtocol:@protocol(YGFileDownloaderDelegate)]&&[self.delegate respondsToSelector:@selector(fileDownloaderFailWithError:)]) {         [self.delegate fileDownloaderFailWithError:error];     } } -(void)connectionDidFinishLoading:(NSURLConnection *)connection{     if ([self.delegate respondsToSelector:@selector(fileDownloaderDidFinishLoad)]) {         [self.delegate fileDownloaderDidFinishLoad];     } } -(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{     [_fileHandle seekToEndOfFile];//设置在末尾追加数据     [_fileHandle writeData:data];//写入数据     _downloadFileSize += data.length;     if ([self.delegate conformsToProtocol:@protocol(YGFileDownloaderDelegate)] && [self.delegate respondsToSelector:@selector(fileDownloader:downloadSize:totalSize:)]) {         [self.delegate fileDownloader:self downloadSize:_downloadFileSize totalSize:_totalFileSize];     } } @end

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