IOS 網路淺析－（十 NSURLSession下載簡介）

之前本來打算在寫兩個篇幅，但是在這片開寫的時候覺得還是寫一個比較好，有利於理解。NSURLSession下載是通過NSURLSession下載代理實現的，上一片也介紹了代理，之所以沒有介紹下載是因為，我個人覺得容易混淆（應該是我太笨）。這篇隨筆里將會介紹NSURLSession下載的實現，包括下載的開始，掛起，繼續。希望本片可以給大家帶來點點收穫。下一篇我打算介紹一下AFN畢竟實際開發中AFN才是硬道理。

//
//  ViewController.m
//  NSURLSession大文件下載
//
//  Created by 大歡 on 16/3/21.
//  Copyright © 2016年 大歡. 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 {
    
    //暫停就是將任務掛起
    
    [self.task cancelByProducingResumeData:^(NSData * _Nullable resumeData) {
        
        //保存已下載的數據
        self.resumeData = resumeData;
    }];
}

- (IBAction)resume:(id)sender {
    
    //可以使用ResumeData創建任務
    
    self.task = [self.session downloadTaskWithResumeData:self.resumeData];
    
    //開啟繼續下載
    [self.task resume];
    
}

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    NSLog(@"%@",NSSearchPathForDirectoriesInDomains(9, 1, 1));
}


/* 
 
 監測臨時文件下載的數據大小，當每次寫入臨時文件時，就會調用一次
 
 bytesWritten 單次寫入多少
 totalBytesWritten  已經寫入了多少
 totalBytesExpectedToWrite 文件總大小
 
 */

- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
    
    //列印下載百分比
    NSLog(@"%f",totalBytesWritten * 1.0 / totalBytesExpectedToWrite);
    
}

//下載完成

- (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