21.文件下载

小文件下载

• 如果文件比较小，下载方式会比较多

  • 直接用 NSData 的 dataWithContentsOfURL 方法

    NSURL *url = [NSURL URLWithString:@"sss"];
    NSData *data = [NSData dataWithContentsOfURL:url];
    

  • 利用 NSURLConnection 发送一个HTTP请求

    //方法一：
      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);
    }];
    方法二：
     NSURL *url = [NSURL URLWithString:@"ss"];
    [NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:url] delegate:self];
    
    //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:@"qq.mp4"];
    // 写入数据
    [self.fileData writeToFile:file atomically:YES];
    self.fileData = nil;
    }
    

  • 如果是下载图片，还可以利用 SDWebImage

大文件下载(不考虑断点下载)

第一种

#define XMGFile [[NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:@"qq.mp4"]

/** 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;

NSURL *url = [NSURL URLWithString:@"qwer"];
[NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:url] delegate:self];

//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(相当于一个指针始终指向文件的最后面)
 [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;
}

第一种

/** 输出流对象 */
@property (nonatomic, strong) NSOutputStream *stream;

[NSURLConnection connectionWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"sss"]] delegate:self];

//NSURLConnectionDataDelegate
 - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
//response.suggestedFilename : 服务器那边的文件名
// 文件路径
NSString *caches = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];
NSString *file = [caches stringByAppendingPathComponent:response.suggestedFilename];

// 利用NSOutputStream往Path中写入数据（append为YES的话，每次写入都是追加到文件尾部）
self.stream = [[NSOutputStream alloc] initToFileAtPath:file append:YES];

// 打开流(如果文件不存在，会自动创建)
[self.stream open];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
 [self.stream write:[data bytes] maxLength:data.length];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
//关闭流
[self.stream close];
}