小文件下载

• 直接用NSData

- (void)dataDownlaod
{
    NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/resources/images/minion_15.png"];

    NSData *data = [NSData dataWithContentsOfURL:url];

    NSLog(@"%zd", data.length);
}

• 利用NSURLConnection发送一个http请求去下载

- (void)connDownload
{
    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);
    }];
}

- (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>
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSHTTPURLResponse *)response
{
    self.contentLength = [response.allHeaderFields[@"Content-Length"] integerValue];
    self.fileData = [NSMutableData data];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.fileData appendData:data];
    CGFloat progress = 1.0 * self.fileData.length / self.contentLength;
    NSLog(@"已下载：%.2f%%", (progress) * 100);
    self.progressView.progress = progress;
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"下载完毕");

    // 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;
}

• 用SDWebImage(第三方下载图片)

大文件下载

• NSFileHandle

/** 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;

- (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];
}

/**
 * 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];

    // 写入数据
    [self.handle writeData:data];

    // 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;
}