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