故事板的绘图:注意各方法与代码关联

代码实现:
#import "ViewController.h"
@interface ViewController ()<NSURLSessionDownloadDelegate>
{

  NSURLSessionDownloadTask *task1;
  NSURLSession *session1;
  NSData *saveData;//已经下载的数据   
}
@property (strong, nonatomic) IBOutlet       UIProgressView *myProgressVIew;
@end

  @implementation ViewController
  //普通下载任务
- (IBAction)downLoadTask:(id)sender {
//1 url
NSURL *url = [NSURL URLWithString:@"http://www.pptbz.com/pptpic/UploadFiles_6909/201204/2012041411433867.jpg"];

//2 request


//3 session
NSURLSession *session = [NSURLSession sharedSession];

//4 task
NSURLSessionDownloadTask *task =[session downloadTaskWithURL:url completionHandler:^(NSURL * _Nullable location, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    
    //location:下载的文件的临时保存的位置(tmp),当block调用完会被删除掉
    NSLog(@"location = %@",location);
    NSLog(@"response = %@",response);//响应头
    
    //移动文件
    NSFileManager *manager = [NSFileManager defaultManager];
    
    NSString *newPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/111.jpg"];
    NSURL *newUrl = [NSURL fileURLWithPath:newPath];
    
    [manager moveItemAtURL:location toURL:newUrl error:nil];
    
    NSLog(@"newsPath = %@",newPath);   
}];

//5 resume
[task resume];

}
  //开启下载
- (IBAction)beginDownLoad:(id)sender {

    //1 url
  // NSURL *url = [NSURL URLWithString:@"http://www.pptbz.com/pptpic/UploadFiles_6909/201204/2012041411433867.jpg"];

  //         NSURL *url = [NSURL URLWithString:@"http://wl.baidu190.com/1470730340/20160879819642dc26a12e0bfc0dc55fda98d5.mp3"];


  NSURL *url = [NSURL URLWithString:@"http://vf1.mtime.cn/Video/2012/04/23/mp4/120423212602431929.mp4"];
//2 request

//3 session
NSURLSessionConfiguration *config = [NSURLSessionConfiguration defaultSessionConfiguration];

session1 = [NSURLSession sessionWithConfiguration:config delegate:self delegateQueue:[NSOperationQueue mainQueue]];

//4 task
task1 =[session1 downloadTaskWithURL:url];

//5 resume
[task1 resume];
  }
//暂停下载
- (IBAction)stopDownLoad:(id)sender {
//1任务取消,所有的数据删除
//    [task cancel];

//2 暂停
[task1 cancelByProducingResumeData:^(NSData * _Nullable resumeData) {
   
    NSLog(@"resumeData = %@",resumeData);//resumeData:已经下载好的数据
    
    saveData = resumeData;
    
    //取消任务之后,把之前的任务丢弃掉
    task1 = nil;//安全释放
    
}];
}
//继续下载
- (IBAction)continueDownLoad:(id)sender {

//重新开始下载任务
task1 =  [session1 downloadTaskWithResumeData:saveData];

//重新开启任务
[task1 resume]; //resume:恢复 下载任务 
}

- (void)viewDidLoad {
[super viewDidLoad];
}
#pragma mark - NSURLdownload Delegate
//已经下载完成后
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location{


//移动文件
NSFileManager *manager = [NSFileManager defaultManager];

NSString *newPath = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents/222.mp4"];
NSURL *newUrl = [NSURL fileURLWithPath:newPath];

[manager moveItemAtURL:location toURL:newUrl error:nil];

NSLog(@"newsPath = %@",newPath);
}

// 数据在传输的过程中,不断调用的方法(每传输一个数据包,就会调用一次)
- (void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask
  didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite{
/*
 bytesWritten:本次下载传输的字节
 totalBytesWritten:已经下载的字节
 totalBytesExpectedToWrite:文件的总大小
 */
NSLog(@"bytesWritten=%lld totalBytesWritten= %lld totalBytesExpectedToWrite= %lld",bytesWritten,totalBytesWritten,totalBytesExpectedToWrite);

//进度
float progress =totalBytesWritten/(float)totalBytesExpectedToWrite;

self.myProgressVIew.progress = progress;
}

@end