#import "YYViewController.h"#import "YYFileMultiDownloader.h"@interface YYViewController ()@property (nonatomic, strong) YYFileMultiDownloader *fileMultiDownloader;@end@implementation YYViewController- (YYFileMultiDownloader *)fileMultiDownloader{  if (!_fileMultiDownloader) {    _fileMultiDownloader = [[YYFileMultiDownloader alloc] init];    // 需要下載的文件遠程URL    _fileMultiDownloader.url = @"http://192.168.1.200:8080/MJServer/resources/jre.zip";    // 文件保存到什么地方    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];    NSString *filepath = [caches stringByAppendingPathComponent:@"jre.zip"];    _fileMultiDownloader.destPath = filepath;  }  return _fileMultiDownloader;}- (void)viewDidLoad{  [super viewDidLoad];  }- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event{  [self.fileMultiDownloader start];}@end

#import <Foundation/Foundation.h>@interface YYFileDownloader : NSObject{  BOOL _downloading;}/** * 所需要下載文件的遠程URL(連接服務器的路徑) */@property (nonatomic, copy) NSString *url;/** * 文件的存儲路徑(文件下載到什么地方) */@property (nonatomic, copy) NSString *destPath;/** * 是否正在下載(有沒有在下載, 只有下載器內部才知道) */@property (nonatomic, readonly, getter = isDownloading) BOOL downloading;/** * 用來監聽下載進度 */@property (nonatomic, copy) void (^progressHandler)(double progress);/** * 開始(恢復)下載 */- (void)start;/** * 暫停下載 */- (void)pause;@end

#import "YYFileDownloader.h" @implementation YYFileDownloader@end下載器類繼承自YYFileDownloader這個類YYFileSingDownloader.h文件#import "YYFileDownloader.h"@interface YYFileSingleDownloader : YYFileDownloader/** * 開始的位置 */@property (nonatomic, assign) long long begin;/** * 結束的位置 */@property (nonatomic, assign) long long end; @endYYFileSingDownloader.m文件#import "YYFileSingleDownloader.h"@interface YYFileSingleDownloader() <NSURLConnectionDataDelegate>/** * 連接對象 */@property (nonatomic, strong) NSURLConnection *conn;/** * 寫數據的文件句柄 */@property (nonatomic, strong) NSFileHandle *writeHandle;/** * 當前已下載數據的長度 */@property (nonatomic, assign) long long currentLength;@end@implementation YYFileSingleDownloader- (NSFileHandle *)writeHandle{  if (!_writeHandle) {    _writeHandle = [NSFileHandle fileHandleForWritingAtPath:self.destPath];  }  return _writeHandle;}/** * 開始(恢復)下載 */- (void)start{  NSURL *url = [NSURL URLWithString:self.url];  // 默認就是GET請求  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];  // 設置請求頭信息  NSString *value = [NSString stringWithFormat:@"bytes=%lld-%lld", self.begin + self.currentLength, self.end];  [request setValue:value forHTTPHeaderField:@"Range"];  self.conn = [NSURLConnection connectionWithRequest:request delegate:self];    _downloading = YES;}/** * 暫停下載 */- (void)pause{  [self.conn cancel];  self.conn = nil;    _downloading = NO;}#pragma mark - NSURLConnectionDataDelegate 代理方法/** * 1. 當接受到服務器的響應(連通了服務器)就會調用 */- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{  }/** * 2. 當接受到服務器的數據就會調用(可能會被調用多次, 每次調用只會傳遞部分數據) */- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{  // 移動到文件的尾部  [self.writeHandle seekToFileOffset:self.begin + self.currentLength];  // 從當前移動的位置(文件尾部)開始寫入數據  [self.writeHandle writeData:data];    // 累加長度  self.currentLength += data.length;    // 打印下載進度  double progress = (double)self.currentLength / (self.end - self.begin);  if (self.progressHandler) {    self.progressHandler(progress);  }}/** * 3. 當服務器的數據接受完畢后就會調用 */- (void)connectionDidFinishLoading:(NSURLConnection *)connection{  // 清空屬性值  self.currentLength = 0;    // 關閉連接(不再輸入數據到文件中)  [self.writeHandle closeFile];  self.writeHandle = nil;}/** * 請求錯誤(失敗)的時候調用(請求超時/斷網/沒有網, 一般指客戶端錯誤) */- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{  }@end

#import "YYFileDownloader.h"@interface YYFileMultiDownloader : YYFileDownloader@end

#import "YYFileMultiDownloader.h"#import "YYFileSingleDownloader.h"#define YYMaxDownloadCount 4@interface YYFileMultiDownloader()@property (nonatomic, strong) NSMutableArray *singleDownloaders;@property (nonatomic, assign) long long totalLength;@end@implementation YYFileMultiDownloader- (void)getFilesize{  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:self.url]];  request.HTTPMethod = @"HEAD";    NSURLResponse *response = nil;#warning 這里要用異步請求  [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];  self.totalLength = response.expectedContentLength;}- (NSMutableArray *)singleDownloaders{  if (!_singleDownloaders) {    _singleDownloaders = [NSMutableArray array];        // 獲得文件大小    [self getFilesize];        // 每條路徑的下載量    long long size = 0;    if (self.totalLength % YYMaxDownloadCount == 0) {      size = self.totalLength / YYMaxDownloadCount;    } else {      size = self.totalLength / YYMaxDownloadCount + 1;    }        // 創建N個下載器    for (int i = 0; i<YYMaxDownloadCount; i++) {      YYFileSingleDownloader *singleDownloader = [[YYFileSingleDownloader alloc] init];      singleDownloader.url = self.url;      singleDownloader.destPath = self.destPath;      singleDownloader.begin = i * size;      singleDownloader.end = singleDownloader.begin + size - 1;      singleDownloader.progressHandler = ^(double progress){        NSLog(@"%d --- %f", i, progress);      };      [_singleDownloaders addObject:singleDownloader];    }        // 創建一個跟服務器文件等大小的臨時文件    [[NSFileManager defaultManager] createFileAtPath:self.destPath contents:nil attributes:nil];        // 讓self.destPath文件的長度是self.totalLengt    NSFileHandle *handle = [NSFileHandle fileHandleForWritingAtPath:self.destPath];    [handle truncateFileAtOffset:self.totalLength];  }  return _singleDownloaders;}/** * 開始(恢復)下載 */- (void)start{  [self.singleDownloaders makeObjectsPerformSelector:@selector(start)];    _downloading = YES;}/** * 暫停下載 */- (void)pause{  [self.singleDownloaders makeObjectsPerformSelector:@selector(pause)];  _downloading = NO;}@end