断点下载

 1 @interface ViewController ()<NSURLConnectionDataDelegate> 2 { 3     // 文件的总大小 4     long long _total; 5     // 当前下载 6     long long _current; 7 } 8  9 // 文件句柄10 @PRoperty (nonatomic,strong)NSFileHandle *fileHandle;11 // 连接对象12 @property (nonatomic,strong)NSURLConnection *conn;13 @property (weak, nonatomic) IBOutlet UiprogressView *progress;14 @property (weak, nonatomic) IBOutlet UIButton *button;15 @end16 17 @implementation ViewController18 - (void)viewDidLoad {19     [super viewDidLoad];20     self.progress.progress = 0;21     // Do any additional setup after loading the view, typically from a nib.22 }23 24 - (IBAction)buttonAction:(UIButton *)sender {25     if ([[sender titleForState:UIControlStateNormal]isEqualToString:@"开始"]) {26         [sender setTitle:@"暂停" forState:(UIControlStateNormal)];27         // 请求28         NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:kUrl]];29         // 设置请求参数30         NSString *rang = [NSString stringWithFormat:@"byte:%lld",_current];31         NSLog(@"request:%@end",request);32         [request setValue:rang forHTTPHeaderField:@"Range"];33          NSLog(@"request:%@end",request);34         // 建立连接35         self.conn = [NSURLConnection connectionWithRequest:request delegate:self];36         // 开始请求37         [_conn start];38     }else{39         [sender setTitle:@"开始" forState:(UIControlStateNormal)];40         // 取消41         [_conn cancel];42     }43 }44 45 - (void)didReceiveMemoryWarning {46     [super didReceiveMemoryWarning];47     // Dispose of any resources that can be recreated.48 }49 50 #pragma mark---delegate51 // 收到响应52 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response53 {54     // 获取总文件大小(总文件的大小在响应里面可以获得)55     _total = response.expectedContentLength;56     // 创建文件57     NSFileManager *manager = [NSFileManager defaultManager];58     NSString *cachesPath  = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES)[0];59     NSString *filePath = [cachesPath stringByAppendingPathComponent:@"music.mp3"];60     NSLog(@"%@",cachesPath);61     // 创建文件62     [manager createFileAtPath:filePath contents:nil attributes:nil];63     // 让文件句柄指向文件64     self.fileHandle = [NSFileHandle fileHandleForWritingAtPath:filePath];65 }66 // 接收到数据67 - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data68 {69     // 计算当前总大小70     _current += data.length;71     // 更新 （在子线程中不能更新UI）72     [self performSelectorOnMainThread:@selector(updateProgress) withObject:self waitUntilDone:YES];73     // 指向文件末尾74     [self.fileHandle seekToEndOfFile];75     // 写数据76     [self.fileHandle writeData:data];77 }78 // 结束79 - (void)connectionDidFinishLoading:(NSURLConnection *)connection80 {81     NSLog(@"下载完毕");82 }83 // 更新progress84 - (void)updateProgress85 {86     self.progress.progress = (long double)_current / (long double)_total;87 }88 89 @end