NSURLSessionDownloadTask大文件断点下载

NSURLSessionDownloadDelegate

#import "ViewController.h"


@interface ViewController () 
/** 下载任务 */
@property (nonatomic, strong) NSURLSessionDownloadTask *task;
@end


@implementation ViewController
/**
 * 开始下载
 */
- (IBAction)start:(id)sender {
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]
                                                          delegate:self
                                                     delegateQueue:[[NSOperationQueue alloc] init]];
    NSString *urlString = @"http://www.example.com:8080/resources/videos/minion_01.mp4";
    NSURL *url = [NSURL URLWithString:urlString];
    self.task = [session downloadTaskWithURL:url];
    [self.task resume];
}

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

/**
 * 继续下载
 */
- (IBAction)goOn:(id)sender {
    [self.task resume];
}

#pragma mark - 

/**
 * 每当写入数据到临时文件时，就会调用一次这个方法
 * totalBytesExpectedToWrite:总大小
 * totalBytesWritten: 已经写入的大小
 * bytesWritten: 这次写入多少
 */
- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
      didWriteData:(int64_t)bytesWritten
 totalBytesWritten:(int64_t)totalBytesWritten
totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite{
    NSLog(@"%s",__func__);
    NSLog(@"%f", 1.0 * totalBytesWritten / totalBytesExpectedToWrite);
}

- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
 didResumeAtOffset:(int64_t)fileOffset
expectedTotalBytes:(int64_t)expectedTotalBytes{
    NSLog(@"%s",__func__);
}

/**
 * 下载完毕就会调用一次这个方法
 */
- (void)URLSession:(NSURLSession *)session
      downloadTask:(NSURLSessionDownloadTask *)downloadTask
didFinishDownloadingToURL:(NSURL *)location{
    // 文件将来存放的真实路径
    NSString *file = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
    NSLog(@"%@",file);
    
    // 剪切location的临时文件到真实路径
    NSFileManager *mgr = [NSFileManager defaultManager];
    [mgr moveItemAtURL:location toURL:[NSURL fileURLWithPath:file] error:nil];
}


- (void)URLSession:(NSURLSession *)session
              task:(NSURLSessionDownloadTask *)task
didCompleteWithError:(NSError *)error{
    NSLog(@"%s",__func__);
}
@end

// 0.996829
// -[ViewController URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:]
// 0.999656
// -[ViewController URLSession:downloadTask:didWriteData:totalBytesWritten:totalBytesExpectedToWrite:]
// 1.000000
// /Users/zhaoyingxin/Library/Developer/CoreSimulator/Devices/1146129D-06F4-457B-83AC-B97F3B7ECA32/data/Containers/Data/Application/265D1E5E-A086-4338-8538-104F6D48663D/Library/Caches/minion_01.mp4
// -[ViewController URLSession:task:didCompleteWithError:]