////  LWTViewController.m//  网络编程练习 -- 大文件下载////  Created by apple on 14-6-28.//  Copyright (c) 2014年 lwt. All rights reserved.//#import "LWTViewController.h"#import "LWTFileDownloadTool.h"@interface LWTViewController () <NSURLConnectionDataDelegate>@property (weak, nonatomic) IBOutlet UIProgressView *progressView;@property (nonatomic, strong) LWTFileDownloadTool *fileDownloadTool;- (IBAction)start : (UIButton *)button;@end@implementation LWTViewController- (LWTFileDownloadTool *)fileDownloadTool{    if (nil == _fileDownloadTool) {//        _fileDownloadTool = [[LWTFileDownloadTool alloc] init];        _fileDownloadTool = [LWTFileDownloadTool fileDownloadTool];                _fileDownloadTool.url = @"http://192.168.1.24:8080/MJServer/resources/video.zip";                NSArray *array = [_fileDownloadTool.url componentsSeparatedByString:@"/"];        NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];        _fileDownloadTool.desturl = [caches stringByAppendingPathComponent:[array lastObject]];                __weak typeof(self) weakVC = self;                _fileDownloadTool.progressHandler = ^(double progress){            weakVC.progressView.progress = progress;        };                _fileDownloadTool.completionHandler = ^(){            NSLog(@"下载完成");        };                _fileDownloadTool.failureHandler = ^(NSError *error){            NSLog(@"%@", error);        };                    }    return _fileDownloadTool;}- (IBAction)start : (UIButton *)button{        if (self.fileDownloadTool.isDownloading) {        [button setTitle:@"恢复" forState:UIControlStateNormal];        [self.fileDownloadTool pause];    }else{        [button setTitle:@"暂停" forState:UIControlStateNormal];        [self.fileDownloadTool begin];    }}@end

////  LWTFileDownloadTool.h//  网络编程练习 -- 大文件下载////  Created by apple on 14-6-28.//  Copyright (c) 2014年 lwt. All rights reserved.//#import <Foundation/Foundation.h>@interface LWTFileDownloadTool : NSObject/** * 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 *desturl;/** * 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);/** * 用来监听下载完毕 */@property (nonatomic, copy) void(^completionHandler)();/** * 用来监听下载失败 */@property (nonatomic, copy) void(^failureHandler)(NSError *error);/** * 开始(恢复)下载 */- (void)begin;/** * 暂停下载 */- (void)pause;+ (instancetype)fileDownloadTool;@end

////  LWTFileDownloadTool.m//  网络编程练习 -- 大文件下载////  Created by apple on 14-6-28.//  Copyright (c) 2014年 lwt. All rights reserved.//#import "LWTFileDownloadTool.h"@interface LWTFileDownloadTool () <NSURLConnectionDataDelegate>@property (nonatomic, strong) NSURLConnection *conn;@property (nonatomic, strong) NSFileHandle *writeHandle;@property (nonatomic, assign) long long totalLength;@property (nonatomic, assign) long long currentLength;@end@implementation LWTFileDownloadTool+ (instancetype)fileDownloadTool{    return [[self alloc] init];}- (void)begin{    _downloading = YES;        NSString *urlStr = [self.url stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];        NSURL *url = [NSURL URLWithString:urlStr];        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];        NSString *value = http://www.mamicode.com/[NSString stringWithFormat:@"bytes=%lld-", self.currentLength];    [request setValue:value forHTTPHeaderField:@"Range"];        self.conn = [NSURLConnection connectionWithRequest:request delegate:self];}- (void)pause{    _downloading = NO;    [self.conn cancel];    self.conn = nil;}#pragma mark - NSURLConnectionDataDelegate- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{        if (self.writeHandle) return;        NSFileManager *manager = [NSFileManager defaultManager];    [manager createFileAtPath:self.desturl contents:nil attributes:nil];        self.writeHandle = [NSFileHandle fileHandleForWritingAtPath:self.desturl];        self.totalLength = response.expectedContentLength;}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    self.currentLength += data.length;        double progress = (double)self.currentLength / self.totalLength;    if (self.progressHandler) {        self.progressHandler(progress);    }        [self.writeHandle seekToEndOfFile];    [self.writeHandle writeData:data];}- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{    if (self.failureHandler) {        self.failureHandler(error);    }}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{    if (self.completionHandler) {        self.completionHandler();    }        self.currentLength = 0;    self.totalLength = 0;        [self.writeHandle closeFile];    self.writeHandle = nil;}@end