ios - 如何获取文件大小以了解是否下载？

Question

我正在使用以下代码从 url 下载 epub/pdf。我想提供一个进度条，这样当我开始下载时它会显示进度，当下载完成时它会弹出一条消息。我该如何实现？

我的下载文件代码

-(void)Download
 {
    NSData *pdfData = [[NSData alloc] initWithContentsOfURL:[NSURL    URLWithString:@"http://www.feedbooks.com/book/3471.epub"]];

    //Store the Data locally as epub  File if u want pdf change the file extension  

    NSString *resourceDocPath = [[NSString alloc] initWithString:[[[[NSBundle mainBundle]  resourcePath] stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"Documents"]];

    NSString *filePath = [resourceDocPath stringByAppendingPathComponent:@"3471.epub"];

    [pdfData writeToFile:filePath atomically:YES];
    NSLog(@"%@",filePath);
 }

我在我的 .m 文件中使用这些代码，但它对我不起作用

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
    _totalFileSize = response.expectedContentLength;
    responseData = [[NSMutableData alloc] init];
}


-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    _receivedDataBytes += [data length];
    MyProgressBar.progress = _receivedDataBytes / (float)_totalFileSize;
    [responseData appendData:data];
}

Answer 1

使用 NSURLConnection

在 .h 文件中

double datalength;
NSMutableData *databuffer;
UIProgressView *progress;

在 .m 文件中

-(void)Download
{
      NSURLConnection *con=[[NSURLConnection alloc]initWithRequest:[NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.feedbooks.com/book/3471.epub"]] delegate:self startImmediately:YES];
      [con start];
}

委托(delegate)方法

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    datalength = [response expectedContentLength];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [databuffer appendData:data];
    progress.progress = (databuffer.length/datalength);
    self.HUD.detailsLabelText = [NSString stringWithFormat:@"Downloading  %.f  %%",(databuffer.length/datalength)*100];
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *resourceDocPath = [[NSString alloc] initWithString:[[[[NSBundle mainBundle]  resourcePath] stringByDeletingLastPathComponent] stringByAppendingPathComponent:@"Documents"]];
    NSString *filePath = [resourceDocPath stringByAppendingPathComponent:@"3471.epub"];
    [pdfData writeToFile:filePath atomically:YES];
    NSLog(@"%@",filePath);
}