iOS NSURLSessionDownloadTask设置代理文件下载的示例

#import "ViewController.h"
@interface ViewController ()<NSURLSessionDownloadDelegate>
@end
@implementation ViewController
-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
  [self delegate];
}

-(void)delegate
{
  //1.url
  NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/images/minion_03.png"];
  
  //2.创建请求对象
  NSURLRequest *request = [NSURLRequest requestWithURL:url];
  
  //3.创建session ：注意代理为NSURLSessionDownloadDelegate
  NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
  
  //4.创建Task
  NSURLSessionDownloadTask *downloadTask = [session downloadTaskWithRequest:request];
  
  //5.执行Task
  [downloadTask resume];
}

#pragma mark ----------------------
#pragma mark NSURLSessionDownloadDelegate
/**
 * 写数据
 *
 * @param session          会话对象
 * @param downloadTask       下载任务
 * @param bytesWritten       本次写入的数据大小
 * @param totalBytesWritten     下载的数据总大小
 * @param totalBytesExpectedToWrite 文件的总大小
 */
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didWriteData:(int64_t)bytesWritten totalBytesWritten:(int64_t)totalBytesWritten totalBytesExpectedToWrite:(int64_t)totalBytesExpectedToWrite
{
  //1. 获得文件的下载进度
  NSLog(@"%f",1.0 * totalBytesWritten/totalBytesExpectedToWrite);
}

/**
 * 当恢复下载的时候调用该方法
 *
 * @param fileOffset     从什么地方下载
 * @param expectedTotalBytes 文件的总大小
 */
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didResumeAtOffset:(int64_t)fileOffset expectedTotalBytes:(int64_t)expectedTotalBytes
{
  NSLog(@"%s",__func__);
}

/**
 * 当下载完成的时候调用
 *
 * @param location   文件的临时存储路径
 */
-(void)URLSession:(NSURLSession *)session downloadTask:(NSURLSessionDownloadTask *)downloadTask didFinishDownloadingToURL:(NSURL *)location
{
  NSLog(@"%@",location);
  
  //1 拼接文件全路径
  NSString *fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:downloadTask.response.suggestedFilename];
  
  //2 剪切文件
  [[NSFileManager defaultManager]moveItemAtURL:location toURL:[NSURL fileURLWithPath:fullPath] error:nil];
  NSLog(@"%@",fullPath);
}

/**
 * 请求结束
 */
-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
  NSLog(@"didCompleteWithError");
}
@end