IOS断点续传

#import "ViewController.h"

@interface ViewController ()<NSURLConnectionDataDelegate,NSURLConnectionDelegate>
{
    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;
}
@property (weak, nonatomic) IBOutlet UILabel *progressLabel;
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;
@property (weak, nonatomic) IBOutlet UIButton *startBtn;
@end

@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    NSLog(@"%@",NSHomeDirectory());
//    NSLog(@"%@",[NSURL URLWithString:[@"http://127.0.0.1/掌厨项目.zip" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]]);
    _url = [NSURL URLWithString:[@"http://127.0.0.1/1.zip" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding]];
}

- (IBAction)download:(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:request delegate:self];
    }
    else
    {
        [sender setTitle:@"开始下载" forState:UIControlStateNormal];
        [_connection cancel];
    }
}

#pragma mark - ConnectionDelegate
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    NSLog(@"%@",error.localizedDescription);
}

//接收到服务端响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    if (!_expectSize) {
        //获取文件真实大小
        _expectSize = response.expectedContentLength;
        _filePath = [NSHomeDirectory() stringByAppendingString:@"/Library/Caches/1.zip"];
        NSFileManager *manager = [NSFileManager defaultManager];
        [manager createFileAtPath:_filePath contents:nil attributes:nil];
        _fileHandle = [NSFileHandle fileHandleForUpdatingAtPath:_filePath];
    }
}

//接收到服务端数据（数据量大时，会调用多次）
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //获取到已经下载的大小
    _readSize += data.length;
//    data writeToFile:<#(NSString *)#> atomically:<#(BOOL)#>
    [_fileHandle seekToEndOfFile];
    [_fileHandle writeData:data];

    CGFloat ratio = 1.0*_readSize/_expectSize;
    _progressLabel.text = [NSString stringWithFormat:@"%.f%%",ratio*100];
    _progressView.progress = ratio;
}

//下载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"下载完成！");
    [_fileHandle closeFile];
}

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

@end