iOS开发网络篇―实现大文件的多线程断点下载

#import "YYViewController.h"#import "YYFileMultiDownloader.h"@interface YYViewController ()@property (nonatomic, strong) YYFileMultiDownloader *fileMultiDownloader;@end@implementation YYViewController- (YYFileMultiDownloader *)fileMultiDownloader{  if (!_fileMultiDownloader) {    _fileMultiDownloader = [[YYFileMultiDownloader alloc] init];    // 需要下载的文件远程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;}/** * 所需要下载文件的远程URL(连接服务器的路径) */@property (nonatomic, copy) NSString *url;/** * 文件的存储路径(文件下载到什么地方) */@property (nonatomic, copy) NSString *destPath;/** * 是否正在下载(有没有在下载, 只有下载器内部才知道) */@property (nonatomic, readonly, getter = isDownloading) BOOL downloading;/** * 用来监听下载进度 */@property (nonatomic, copy) void (^progressHandler)(double progress);/** * 开始(恢复)下载 */- (void)start;/** * 暂停下载 */- (void)pause;@end

#import "YYFileDownloader.h" @implementation YYFileDownloader@end下载器类继承自YYFileDownloader这个类YYFileSingDownloader.h文件#import "YYFileDownloader.h"@interface YYFileSingleDownloader : YYFileDownloader/** * 开始的位置 */@property (nonatomic, assign) long long begin;/** * 结束的位置 */@property (nonatomic, assign) long long end; @endYYFileSingDownloader.m文件#import "YYFileSingleDownloader.h"@interface YYFileSingleDownloader() <NSURLConnectionDataDelegate>/** * 连接对象 */@property (nonatomic, strong) NSURLConnection *conn;/** * 写数据的文件句柄 */@property (nonatomic, strong) NSFileHandle *writeHandle;/** * 当前已下载数据的长度 */@property (nonatomic, assign) long long currentLength;@end@implementation YYFileSingleDownloader- (NSFileHandle *)writeHandle{  if (!_writeHandle) {    _writeHandle = [NSFileHandle fileHandleForWritingAtPath:self.destPath];  }  return _writeHandle;}/** * 开始(恢复)下载 */- (void)start{  NSURL *url = [NSURL URLWithString:self.url];  // 默认就是GET请求  NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];  // 设置请求头信息  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;}/** * 暂停下载 */- (void)pause{  [self.conn cancel];  self.conn = nil;    _downloading = NO;}#pragma mark - NSURLConnectionDataDelegate 代理方法/** * 1. 当接受到服务器的响应(连通了服务器)就会调用 */- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{  }/** * 2. 当接受到服务器的数据就会调用(可能会被调用多次, 每次调用只会传递部分数据) */- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{  // 移动到文件的尾部  [self.writeHandle seekToFileOffset:self.begin + self.currentLength];  // 从当前移动的位置(文件尾部)开始写入数据  [self.writeHandle writeData:data];    // 累加长度  self.currentLength += data.length;    // 打印下载进度  double progress = (double)self.currentLength / (self.end - self.begin);  if (self.progressHandler) {    self.progressHandler(progress);  }}/** * 3. 当服务器的数据接受完毕后就会调用 */- (void)connectionDidFinishLoading:(NSURLConnection *)connection{  // 清空属性值  self.currentLength = 0;    // 关闭连接(不再输入数据到文件中)  [self.writeHandle closeFile];  self.writeHandle = nil;}/** * 请求错误(失败)的时候调用(请求超时/断网/没有网, 一般指客户端错误) */- (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 这里要用异步请求  [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:nil];  self.totalLength = response.expectedContentLength;}- (NSMutableArray *)singleDownloaders{  if (!_singleDownloaders) {    _singleDownloaders = [NSMutableArray array];        // 获得文件大小    [self getFilesize];        // 每条路径的下载量    long long size = 0;    if (self.totalLength % YYMaxDownloadCount == 0) {      size = self.totalLength / YYMaxDownloadCount;    } else {      size = self.totalLength / YYMaxDownloadCount + 1;    }        // 创建N个下载器    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];    }        // 创建一个跟服务器文件等大小的临时文件    [[NSFileManager defaultManager] createFileAtPath:self.destPath contents:nil attributes:nil];        // 让self.destPath文件的长度是self.totalLengt    NSFileHandle *handle = [NSFileHandle fileHandleForWritingAtPath:self.destPath];    [handle truncateFileAtOffset:self.totalLength];  }  return _singleDownloaders;}/** * 开始(恢复)下载 */- (void)start{  [self.singleDownloaders makeObjectsPerformSelector:@selector(start)];    _downloading = YES;}/** * 暂停下载 */- (void)pause{  [self.singleDownloaders makeObjectsPerformSelector:@selector(pause)];  _downloading = NO;}@end