2016 - 1- 23 大文件下载

---恢复内容开始---

一: 利用NSFileHandle对象实现大文件下载

 1.要了解NSFileHandle的用法，注意下载完要关闭这个对象。还要记得每次写入之前将它的文件指针挪位！

//
//  ViewController.m
//  多值参数
//
//  Created by Mac on 16/1/23.
//  Copyright © 2016年 Mac. All rights reserved.
//

#define ZZFile  [ [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingString:@"minion_15.mp4"]

#import "ViewController.h"

@interface ViewController ()<NSURLConnectionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *proView;
//@property (nonatomic, strong) NSMutableData *fileData;

@property (nonatomic, assign) NSInteger contentLength;
@property (nonatomic, assign) NSInteger currentLength;

@property (nonatomic, strong) NSFileHandle *handle;


//@property (nonatomic, strong) UIImage *image;

@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    //  这种方法没法暂停，只适合下载小文件
    
    NSURL *url = [[NSURL alloc] initWithString:@"http://120.25.226.186:32812/resources/videos/minion_15.mp4" ];
    NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
    // 设置connect的代理
    [NSURLConnection connectionWithRequest:request delegate:self];
}
#pragma mark - NSURLConnect 的代理

// connection接收到响应,此时应当创建数据准备拼接data
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response
{
    NSHTTPURLResponse *newResponse = response;
    
    // 获得文件的总长度
    self.contentLength = [newResponse.allHeaderFields[@"Content-Length"] integerValue];

    // 创建一个空的文件
    [[NSFileManager defaultManager] createFileAtPath:ZZFile contents:nil attributes:nil];
    
    self.handle = [NSFileHandle fileHandleForWritingAtPath:ZZFile];

}

// 接收到了数据，这个方法会被多次调用，需要在这里拼接数据
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
// 接收到数据后写入文件
    // 设置当前下载量
    self.currentLength += data.length;
    
    // 制定文件的写入位置，在当前文件的最后面
    [self.handle seekToEndOfFile];
    
    // 写入数据
    [self.handle writeData:data];
    
    self.proView.progress = 1.0 * self.currentLength / self.contentLength;
    
}

// 下载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    // 下载完毕后需要关闭handle
    [self.handle closeFile];
    
    self.handle = nil;
    
    self.currentLength = 0;
    
}


@end