iOS之网络下载文件

文件下载

文件下载在我们日常开发中经常使用到，比如:图片，音频，视频等

简单的小文件下载

• get异步下载

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSString *urlStr =  @"https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1560231628392&di=1ea41537c16f8045d212ef09b24746cc&imgtype=0&src=http%3A%2F%2Fg.hiphotos.baidu.com%2Fzhidao%2Fpic%2Fitem%2F7acb0a46f21fbe094542faa760600c338744ad60.jpg";
    
    NSURL *url = [NSURL URLWithString:urlStr];
    
    //创建请求
    NSURLRequest *requst = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];
    //创建一个线程
    NSOperationQueue *queue = [[NSOperationQueue alloc] init];
    
    [NSURLConnection sendAsynchronousRequest:requst queue:queue completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
        //data是下载的数据
         UIImage *image = [UIImage imageWithData:data];
        //回到主线程
        [[NSOperationQueue mainQueue] addOperationWithBlock:^{
            self.imageView.image = image;
        }];
        
        
    }];
 
 
    
}

• 代理方法 监听就现在
  用本地服务器下载一个短视频 本地服务器的搭建可以点击这里查看

//懒加载 属性
- (NSMutableData *)finData {
    if (!_finData) {
        _finData = [NSMutableData data];
    }
    return _finData;
}

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSString *urlStr =  @"http://localhost/video.mp4";
    
    NSURL *url = [NSURL URLWithString:urlStr];
    
    //创建请求
    NSURLRequest *requst = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];
    
    //设置代理 遵循协议
    [[NSURLConnection alloc] initWithRequest:requst delegate:self];
 
}


//收到响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    //获取到 总数据的大小
    self.totalLength = response.expectedContentLength;
    
    
}

//接受数据
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    //拼接数据
    [self.finData appendData:data];
    //计算下载
    NSLog(@"%f",  1.0 *self.finData.length/self.totalLength);
    
}

//失败的时候
- (void)connection:(NSURLConnection *)connection didFailWithError:(nonnull NSError *)error{
    
}

//加载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
//    NSLog(@"完成---%@",self.finData);
    self.finData = nil;
}

大文件下载

• NSFileManager点击这里查看
• NSFileHandle文件句柄 指针 ，注意:在不用这个对象实例的时候，一定要关闭

当大文件在 下载的时候，我们需要用到NSFileHandle指针类指向，接受文件的数据拼接成一个完成的数据,当然我们也需要NSFileManager创建一个空文件来存储接受的数据

- (void)viewDidLoad {
    [super viewDidLoad];
    
    NSString *urlStr =  @"http://localhost/video.mp4";
    
    NSURL *url = [NSURL URLWithString:urlStr];
    
    //创建请求
    NSURLRequest *requst = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];
    
    [[NSURLConnection alloc] initWithRequest:requst delegate:self];
 
 
    
}

//收到响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    
    self.totalLength = response.expectedContentLength;
    
    //获取文件路径
    NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject;
    self.fullpath = [cachePath stringByAppendingPathComponent:@"123.mp4"];
    
    //创建一个空文件
    
    [[NSFileManager defaultManager] createFileAtPath:self.fullpath  contents:nil attributes:nil];
    
    //创建文件指针
    self.handle = [NSFileHandle fileHandleForWritingAtPath:self.fullpath];
    
    
    
}

//接受数据
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
   
    
    self.currentLegth += data.length;
    
    //接受到数据时 将指针 移动数据的末尾
    [self.handle seekToEndOfFile];
    
    //写入文件
    [self.handle writeData:data];
    
    NSLog(@"%f",1.0 * self.currentLegth/self.totalLength);
    
    
}

//失败的时候
- (void)connection:(NSURLConnection *)connection didFailWithError:(nonnull NSError *)error{
    
}

//加载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{

    //下载完成关闭 指针
    [self.handle closeFile];
    self.handle = nil;
}

断点下载

• 主要是设置请求头的内容
• 原理:根据当前下载文件的大小(记录)，设置到请求头再次下载的时候，从当前记录的位置开始下载

///开始下载
- (IBAction)handleStartAction:(UIButton *)sender {
    NSString *urlStr =  @"http://localhost/video.mp4";
    
    NSURL *url = [NSURL URLWithString:urlStr];
    
    //创建请求
    NSMutableURLRequest *requst = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:15];
    //设置请求头
    //从当前在下在文件的大小 开始下载 self.currentLegth 记录之前下载的位置
    NSString *rangeByte = [NSString stringWithFormat:@"bytes=%zd-",self.currentLegth];
    
    [requst setValue:rangeByte forHTTPHeaderField:@"Range"];
    
  self.connection  = [[NSURLConnection alloc] initWithRequest:requst delegate:self];
    
}

///取消i下载

- (IBAction)handleCancleAction:(UIButton *)sender {
   
    [self.connection cancel];
    
}


//收到响应
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    
    //再次下载的时候，如果已经存在了，就直接return,从记录的位置下载
    if (self.currentLegth > 0) {
        
        return;
    }
    
    self.totalLength = response.expectedContentLength;
    
    //获取文件路径
    NSString *cachePath = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES).lastObject;
    self.fullpath = [cachePath stringByAppendingPathComponent:@"123.mp4"];
    
    //创建一个空文件
    
    [[NSFileManager defaultManager] createFileAtPath:self.fullpath  contents:nil attributes:nil];
    
    //创建文件指针
    self.handle = [NSFileHandle fileHandleForWritingAtPath:self.fullpath];
    
    
    
    
}

//接受数据
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    
    
    self.currentLegth += data.length;
   
    
    //接受到数据时 将指针 移动数据的末尾
    [self.handle seekToEndOfFile];
    
    //写入文件
    [self.handle writeData:data];
    
    self.proviessView.progress = 1.0 * self.currentLegth/self.totalLength;
    
    NSLog(@"%f",1.0 * self.currentLegth/self.totalLength);
    
    
}

//失败的时候
- (void)connection:(NSURLConnection *)connection didFailWithError:(nonnull NSError *)error{
    
}

//加载完成
- (void)connectionDidFinishLoading:(NSURLConnection *)connection{
    
    //下载完成关闭 指针
    [self.handle closeFile];
    self.handle = nil;
}