iOS-NSURLConnection实现大文件断点下载

#import "ViewController.h"

@interface ViewController ()<NSURLConnectionDataDelegate>
@property (weak, nonatomic) IBOutlet UIProgressView *progressView;

@property (nonatomic, assign) NSInteger totalSize;
@property (nonatomic, assign) NSInteger currentSize;
/** 文件句柄 (文件处理者)*/
@property (nonatomic, strong)NSFileHandle *handle;
/** 沙盒路径 */
@property (nonatomic, strong) NSString *fullPath;
/** 连接对象 */
@property (nonatomic, strong) NSURLConnection *connect;
@end

@implementation ViewController

//开始下载
- (IBAction)startBtnClick:(id)sender {
    [self download];
}
//取消下载
- (IBAction)cancelBtnClick:(id)sender {
    [self.connect cancel];
}
//继续下载
- (IBAction)goOnBtnClick:(id)sender {
    [self download];
}

//内存飙升
-(void)download
{
    //1.url
    // NSURL *url = [NSURL URLWithString:@"http://imgsrc.baidu.com/forum/w%3D580/sign=54a8cc6f728b4710ce2ffdc4f3cec3b2/d143ad4bd11373f06c0b5bd1a40f4bfbfbed0443.jpg"];
    
    NSURL *url = [NSURL URLWithString:@"http://www.33lc.com/article/UploadPic/2012-10/2012102514201759594.jpg"];
    
    //2.创建请求对象
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    
    //设置请求头信息,告诉服务器值请求一部分数据range
    /*
     bytes=0-100 
     bytes=-100
     bytes=0- 请求100之后的所有数据
     */
    NSString *range = [NSString stringWithFormat:@"bytes=%zd-",self.currentSize];
    [request setValue:range forHTTPHeaderField:@"Range"];
    NSLog(@"+++++++%@",range);
    
    //3.发送请求
    NSURLConnection *connect = [[NSURLConnection alloc]initWithRequest:request delegate:self];
   
    //赋给全局属性
    self.connect = connect;
}

#pragma mark NSURLConnectionDataDelegate

//接收带响应
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSLog(@"didReceiveResponse");
    
    //1.得到文件的总大小(本次请求的文件数据的总大小 != 文件的总大小)
    // self.totalSize = response.expectedContentLength + self.currentSize;
    
    if (self.currentSize >0) {
        return;
    }
    
    self.totalSize = response.expectedContentLength;
    
    //2.写数据到沙盒中
    self.fullPath = [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject]stringByAppendingPathComponent:@"123.jpg"];
    
    NSLog(@"%@",self.fullPath);
    
    //3.创建一个空的文件
    [[NSFileManager defaultManager] createFileAtPath:self.fullPath contents:nil attributes:nil];
    
    //NSDictionary *dict = [[NSFileManager defaultManager]attributesOfItemAtPath:self.fullPath error:nil];
    
    //4.创建文件句柄(指针)
    self.handle = [NSFileHandle fileHandleForWritingAtPath:self.fullPath];
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //1.移动文件句柄到数据的末尾
    [self.handle seekToEndOfFile];
    
    //2.写数据
    [self.handle writeData:data];
    
    //3.获得进度
    self.currentSize += data.length;
    
    //进度=已经下载/文件的总大小
    NSLog(@"%f",1.0 *  self.currentSize/self.totalSize);
    self.progressView.progress = 1.0 *  self.currentSize/self.totalSize;
    //NSLog(@"%@",self.fullPath);
}
/**
对于 NSURLConnection 和 NSURLDownload，在[challenge sender] 上调用continueWithoutCredentialsForAuthenticationChallenge:方法。不提供证书的话，可能会导致连接失败，调用connectionDidFailWithError:方法 ，或者会返回一个不需要验证身份的替代的URL。
*/
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
}

//请求结束时调用
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    //1.关闭文件句柄
    [self.handle closeFile];
    self.handle = nil;
    
    NSLog(@"connectionDidFinishLoading");
    NSLog(@"%@",self.fullPath);
}
@end