之前本来打算在写两个篇幅，但是在这片开写的时候觉得还是写一个比较好，有利于理解。NSURLSession下载是通过NSURLSession下载代理实现的，上一片也介绍了代理，之所以没有介绍下载是因为，我个人觉得容易混淆（应该是我太笨）。这篇随笔里将会介绍NSURLSession下载的实现，包括下载的开始，挂起，继续。希望本片可以给大家带来点点收获。下一篇我打算介绍一下AFN毕竟实际开发中AFN才是硬道理。
//
// ViewController.m
// NSURLSession大文件下载
//
// Created by 大欢 on 16/3/21.
// Copyright © 2016年 大欢. All rights reserved.
// #import "ViewController.h" @interface ViewController ()<NSURLSessionDownloadDelegate> @property (nonatomic, strong) NSURLSessionDownloadTask * task; @property (nonatomic, strong) NSData * resumeData; @property (nonatomic, strong) NSURLSession * session; @end @implementation ViewController - (IBAction)start:(id)sender { NSURLSession * session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[[NSOperationQueue alloc] init]]; self.session = session; self.task = [session downloadTaskWithURL:[NSURL URLWithString:[@"http://192.168.1.200/DOM解析.mp4"stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]]; [self.task resume];
} - (IBAction)pause:(id)sender { //暂停就是将任务挂起 [self.task cancelByProducingResumeData:^(NSData * _Nullable resumeData) { //保存已下载的数据
self.resumeData = resumeData;
}];
} - (IBAction)resume:(id)sender { //可以使用ResumeData创建任务 self.task = [self.session downloadTaskWithResumeData:self.resumeData]; //开启继续下载
[self.task resume]; } - (void)viewDidLoad {
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib. NSLog(@"%@",NSSearchPathForDirectoriesInDomains(, , ));
} /* 监测临时文件下载的数据大小，当每次写入临时文件时，就会调用一次 bytesWritten 单次写入多少
totalBytesWritten 已经写入了多少
totalBytesExpectedToWrite 文件总大小 */ - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didWriteData:(int64_t)bytesWritten
totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite { //打印下载百分比
NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite); } //下载完成 - (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location { NSString * cachesPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename]; NSFileManager * mgr = [NSFileManager defaultManager]; [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:cachesPath] error:NULL]; } - (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error { NSLog(@"%@",error);
} - (void)didReceiveMemoryWarning {
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
} @end