ios -断点下载

//
//  ViewController.m
//  downLoadTask代理
//
//  Created by 泛在吕俊衡 on 2017/6/16.
//  Copyright © 2017年 anjohnlv. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()

@property (nonatomic, strong) NSURLSession *session;
@property (nonatomic, strong) NSURLSessionDownloadTask *downloadTask;
@property (nonatomic, strong) NSData *resumeData;
@end

@implementation ViewController
/*
 NSURLSessionDownloadTask：可以在后台继续下载，适用下载一些大文件
 NSURLSessionDataTask：不可以在后台继续下载，适用一帮数据获取
 NSURLSessionDataTask：适用于上传文件
 */

-(NSData *)resumeData {
    if (_resumeData==nil) {
        _resumeData=[[NSData alloc] init];
    }
    return _resumeData;
}

-(NSURLSession *)session {
//    创建会话
    if (_session==nil) {
        _session=[NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    }
    return _session;
}

-(NSURLSessionDownloadTask *)downloadTask {
//    创建任务
    if (_downloadTask==nil) {
        NSURL *url=[NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_01.mp4"];
        NSURLRequest *request=[[NSURLRequest alloc] initWithURL:url];
        _downloadTask =[self.session downloadTaskWithRequest:request];
    }
    return _downloadTask;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
}

- (IBAction)start:(id)sender {
//    开始下载 
    [self.downloadTask resume];
}

- (IBAction)pause:(id)sender {
    //暂停下载
    [self.downloadTask suspend];
}

- (IBAction)cancle:(id)sender {
    //取消下载
    [self.downloadTask cancelByProducingResumeData:^(NSData * _Nullable resumeData) {
//        当前已经下载的内容
        self.resumeData=resumeData;
    }];
}

- (IBAction)goon:(id)sender {
//    继续下载
    if (self.resumeData.length>0) {
       self.downloadTask= [self.session downloadTaskWithResumeData:self.resumeData];
    }
    [self.downloadTask resume];
}


/* Sent periodically to notify the delegate of download progress. */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite {
    //下载进度
    NSLog(@"offet:%f", 1.0*totalBytesWritten/totalBytesExpectedToWrite);
}

/* Sent when a download has been resumed. If a download failed with an
 * error, the -userInfo dictionary of the error will contain an
 * NSURLSessionDownloadTaskResumeData key, whose value is the resume
 * data.
 */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
 didResumeAtOffset:(int64_t)fileOffset
expectedTotalBytes:(int64_t)expectedTotalBytes{
    
    NSLog(@"offet:%lli   %lli", fileOffset, expectedTotalBytes);
    
}


/* Sent when a download task that has completed a download.  The delegate should
 * copy or move the file at the given location to a new location as it will be
 * removed when the delegate message returns. URLSession:task:didCompleteWithError: will
 * still be called.
 */
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location {
    
    //文件临时下载地址
    NSLog(@"location:%@",location);
    NSString *filepath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES).lastObject stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
//    将文件移到本地文件夹内
    [[NSFileManager defaultManager] moveItemAtURL:location toURL:[NSURL URLWithString:filepath] error:nil];
    NSLog(@"%@",filepath);
}
@end