通过设置代理我们可以拿到下载进度，对于大文件，我们还需要做到开始、暂停、继续以及取消等相应操作，这篇文章先简单的介绍一下通过代理来实现文件下载的问题：
#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
