AFNetworking 3.0 AFHTTPSessionManager文件下载

#import "ViewController.h"
#import <AFNetworking.h>  

@interface ViewController ()  

- (IBAction)start:(UIButton *)sender;  

- (IBAction)pause:(UIButton *)sender;  

@property (weak, nonatomic) IBOutlet UIProgressView *pro;  

@property(nonatomic,strong) NSURLSessionDownloadTask *task;  

@end  

@implementation ViewController  

-(NSURLSessionDownloadTask *)task{  

    if (!_task) {  

        AFHTTPSessionManager *session=[AFHTTPSessionManager manager];  

        NSURLRequest *request=[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_01.mp4"]];  

        _task=[session downloadTaskWithRequest:request progress:^(NSProgress * _Nonnull downloadProgress) {  

            //下载进度
            NSLog(@"%@",downloadProgress);  

            [[NSOperationQueue mainQueue] addOperationWithBlock:^{  

                self.pro.progress=downloadProgress.fractionCompleted;  

            }];  

        } destination:^NSURL * _Nonnull(NSURL * _Nonnull targetPath, NSURLResponse * _Nonnull response) {  

            //下载到哪个文件夹
            NSString *cachePath=NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).firstObject;  

            NSString *fileName=[cachePath stringByAppendingPathComponent:response.suggestedFilename];  

            return [NSURL fileURLWithPath:fileName];  

        } completionHandler:^(NSURLResponse * _Nonnull response, NSURL * _Nullable filePath, NSError * _Nullable error) {  

            //下载完成了
            NSLog(@"下载完成了 %@",filePath);
        }];
    }  

    return _task;
}  

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

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];  

}  

- (IBAction)start:(UIButton *)sender {  

    [self.task resume];
}  

- (IBAction)pause:(UIButton *)sender {  

    [self.task suspend];
}
@end