////  ViewController.m//  06-掌握-小文件下载#import "ViewController.h"@interface ViewController () <NSURLConnectionDataDelegate>@property (weak, nonatomic) IBOutlet UIProgressView *progressView;/** 文件数据 */@property (nonatomic, strong) NSMutableData *fileData;/** 文件的总长度 */@property (nonatomic, assign) NSInteger contentLength;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];    //要请求url文件    NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_15.mp4"];    [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:url] delegate:self];//使用代理}#pragma mark - <NSURLConnectionDataDelegate>- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{　　//接收到了响应；    self.contentLength = [response.allHeaderFields[@"Content-Length"] integerValue];
　　//拿到响应头，得到下载文件的总大小，目的计算下载的百分比；
　　//self.contentLength 要拿到下面用，so给了个强引用；
    self.fileData = [NSMutableData data];//接收到响应后，才创建这个临时存放数据的数据对象；要拿到写入沙盒那一步使用；}- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{　　//不断的收数据，数据的拼接；收一点写一点去沙盒；    [self.fileData appendData:data];    CGFloat progress = 1.0 * self.fileData.length / self.contentLength;//下载百分比    NSLog(@"已下载：%.2f%%", (progress) * 100);    self.progressView.progress = progress;}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{　　//上一步的数据收集完了；    NSLog(@"下载完毕"); //来到缓存沙盒路径，拼接文件路径，将收完的数据写入这个文件路径，临时的存放数据对象清空；        // 将文件写入沙盒中        // 缓存文件夹    NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];        // 文件路径    NSString *file = [caches stringByAppendingPathComponent:@"minion_15.mp4"];        // 写入数据    [self.fileData writeToFile:file atomically:YES];    self.fileData = nil;}- (void)connDownload{　　//异步请求网路图片；    NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/images/minion_15.png"];    [NSURLConnection sendAsynchronousRequest:[NSURLRequest requestWithURL:url] queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {        NSLog(@"%zd", data.length);    }];}//文件下载其实就是get请求，能发get请求的就能下载；- (void)dataDownlaod{　　//使用网络上的图片；    NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/images/minion_15.png"];    //适合下载小文件；没有办法断点下载，暂停    NSData *data =http://www.mamicode.com/ [NSData dataWithContentsOfURL:url];        NSLog(@"%zd", data.length);}@end

//  ViewController.m//  06-掌握-小文件下载#import "ViewController.h"#define XMGFile [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"minion_15.mp4"]@interface ViewController () <NSURLConnectionDataDelegate>@property (weak, nonatomic) IBOutlet UIProgressView *progressView;/** 文件的总长度 */@property (nonatomic, assign) NSInteger contentLength;/** 当前下载的总长度 */@property (nonatomic, assign) NSInteger currentLength;/** 文件句柄对象 */@property (nonatomic, strong) NSFileHandle *handle;@end@implementation ViewController- (void)viewDidLoad {    [super viewDidLoad];        NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/videos/minion_15.mp4"];    [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:url] delegate:self];}#pragma mark - <NSURLConnectionDataDelegate>/** * 接收到响应的时候：创建一个空的文件 */- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response{    // 获得文件的总长度    self.contentLength = [response.allHeaderFields[@"Content-Length"] integerValue];        // 创建一个空的文件    [[NSFileManager defaultManager] createFileAtPath:XMGFile contents:nil attributes:nil];        // 创建文件句柄    self.handle = [NSFileHandle fileHandleForWritingAtPath:XMGFile];//fileHandlewritingAtPath用来写文件的}/** * 接收到具体数据：马上把数据写入一开始创建好的文件 */- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{    // 指定数据的写入位置 -- 文件内容的最后面    [self.handle seekToEndOfFile];//挪到最后面        // 写入数据    [self.handle writeData:data];//从最后面开始写入数据；        // 拼接总长度    self.currentLength += data.length;        // 进度    self.progressView.progress = 1.0 * self.currentLength / self.contentLength;}- (void)connectionDidFinishLoading:(NSURLConnection *)connection{    // 关闭handle    [self.handle closeFile];    self.handle = nil;        // 清空长度    self.currentLength = 0;}@end