ios开发网络学习十：利用文件句柄实现大文件下载

#import "ViewController.h"

@interface ViewController ()<NSURLSessionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *proessView;
/** 接受响应体信息 */
@property (nonatomic, strong) NSFileHandle *handle;
@property (nonatomic, assign) NSInteger totalSize;
@property (nonatomic, assign) NSInteger currentSize;
@property (nonatomic, strong) NSString *fullPath;
@end

@implementation ViewController

-(void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event
{
//1.url
NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_02.mp4"];

//2.创建请求对象
NSURLRequest *request = [NSURLRequest requestWithURL:url];

//3.创建会话对象,设置代理
/*
第一个参数:配置信息 [NSURLSessionConfiguration defaultSessionConfiguration]
第二个参数:代理
第三个参数:设置代理方法在哪个线程中调用
*/
NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];

//4.创建Task
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request];

//5.执行Task
[dataTask resume];
}

#pragma mark ----------------------
#pragma mark NSURLSessionDataDelegate
/**
*  1.接收到服务器的响应 它默认会取消该请求
*
*  @param session           会话对象
*  @param dataTask          请求任务
*  @param response          响应头信息
*  @param completionHandler 回调 传给系统
*/
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler
{
//获得文件的总大小
self.totalSize = response.expectedContentLength;

//获得文件全路径
self.fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:response.suggestedFilename];

//创建空的文件
[[NSFileManager defaultManager]createFileAtPath:self.fullPath contents:nil attributes:nil];

//创建文件句柄
self.handle = [NSFileHandle fileHandleForWritingAtPath:self.fullPath];

[self.handle seekToEndOfFile];
/*
NSURLSessionResponseCancel = 0,取消 默认
NSURLSessionResponseAllow = 1, 接收
NSURLSessionResponseBecomeDownload = 2, 变成下载任务
NSURLSessionResponseBecomeStream        变成流
*/
completionHandler(NSURLSessionResponseAllow);
}

/**
*  接收到服务器返回的数据 调用多次
*
*  @param session           会话对象
*  @param dataTask          请求任务
*  @param data              本次下载的数据
*/
-(void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data
{

//写入数据到文件
[self.handle writeData:data];

//计算文件的下载进度
self.currentSize += data.length;
NSLog(@"%f",1.0 * self.currentSize / self.totalSize);

self.proessView.progress = 1.0 * self.currentSize / self.totalSize;
}

/**
*  请求结束或者是失败的时候调用
*
*  @param session           会话对象
*  @param dataTask          请求任务
*  @param error             错误信息
*/
-(void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error
{
NSLog(@"%@",self.fullPath);

//关闭文件句柄
[self.handle closeFile];
self.handle = nil;
}

@end