IOS 断点下载

//
//  ViewController.m
//  UI4_断点下载
//
//  Created by qianfeng on 15/8/19.
//  Copyright (c) 2015年 ZBC. All rights reserved.
//

#import "ViewController.h"

@interface ViewController ()<NSURLConnectionDelegate,NSURLConnectionDataDelegate>
{
    NSURL *_url;
    NSURLConnection *_connection;
    //文件读写
    NSFileHandle *_fileHandle;
    //下载文件保存路径
    NSString *_filePath;
    //文件真实大小
    long long _expectSize;
    
    //已经下载的大小
    long long _readSize;
}
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view, typically from a nib.
    
    _url=[NSURL URLWithString:[@"http://192.168.84.188/新版上线流程整理.pdf" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];//解码
    NSLog(@"%@",NSHomeDirectory());
    
    NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];
    _expectSize=[[defaults objectForKey:@"xpectsize"] longLongValue];
    if (_expectSize) {
        _filePath=[NSHomeDirectory() stringByAppendingString:@"/Library/Caches/新版上线流程整理.pdf"];
        _fileHandle=[NSFileHandle fileHandleForUpdatingAtPath:_filePath];
        _readSize=[_fileHandle readDataToEndOfFile].length;
        
        CGFloat ratio=1.0*_readSize/_expectSize;
        _progressLabel.text=[NSString stringWithFormat:@"%.2f%%",ratio*100];
        _progressView.progress=ratio;
    }
}

- (void)didReceiveMemoryWarning {
    [super didReceiveMemoryWarning];
    // Dispose of any resources that can be recreated.
}

- (IBAction)startBtn:(UIButton *)sender {
    if ([sender.titleLabel.text isEqualToString:@"开始下载"]) {
        [sender setTitle:@"暂停" forState:UIControlStateNormal];
        
        NSMutableURLRequest *request=[NSMutableURLRequest requestWithURL:_url];
        NSString *range=[NSString stringWithFormat:@"bytes=%lld-",_readSize];
        [request setValue:range forHTTPHeaderField:@"Range"];
        _connection=[[NSURLConnection alloc] initWithRequest:[NSURLRequest requestWithURL:_url] delegate:self];
    }
    else
    {
        [sender setTitle:@"开始下载" forState:UIControlStateNormal];
        [_connection cancel];
    }
    
    
    
    
}

#pragma mark---下载协议
//下载错误
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"%@",error.localizedDescription);
}

//接收到数据
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //获取到 下载的大小
    _readSize+=data.length;
    
    //一直追加
    [_fileHandle seekToEndOfFile];
    [_fileHandle writeData:data];
    
    CGFloat ratio=1.0*_readSize/_expectSize;
    _progressLabel.text=[NSString stringWithFormat:@"%.2f%%",ratio*100];
    _progressView.progress=ratio;
}
//接收到响应
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"%lld",_expectSize);
    if (!_expectSize) {
        _filePath=[NSHomeDirectory() stringByAppendingString:@"/Library/Caches/新版上线流程整理.pdf"];
        NSLog(@"%@",_filePath);
        _expectSize=response.expectedContentLength;

        NSFileManager *manager=[NSFileManager defaultManager];
        if (![manager fileExistsAtPath:_filePath]) {
            [manager createFileAtPath:_filePath contents:nil attributes:nil];
        }
        
        _fileHandle=[NSFileHandle fileHandleForUpdatingAtPath:_filePath];
     
        
        NSUserDefaults *defaults=[NSUserDefaults standardUserDefaults];
        [defaults setObject:@(_expectSize) forKey:@"xpectsize"];
        [defaults synchronize];
    }
    
    
    
}
//下载完成
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"下载完成");
    [_fileHandle closeFile];
}

@end