Question

这是我使用NSUrlConnection下载pdf文件并将其下载到文档目录的代码。

-(void)startDownloadFile:(UIButton *)sender
{
    ResourceTelephones * resource = [array objectAtIndex:sender.tag];

    NSString * currentURL = resource.website;
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:currentURL]];

    NSURLConnection *conn = [[NSURLConnection alloc] init];
    (void)[conn initWithRequest:request delegate:self];

    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH, 0ul);
    dispatch_async(queue, ^{
        NSData * data = [NSData dataWithContentsOfURL:[NSURL URLWithString:currentURL]];
        dispatch_sync(dispatch_get_main_queue(), ^{
        });
       NSString * filePath = [[self applicationDocumentsDirectory] stringByAppendingPathComponent:[NSString stringWithFormat:@"myPDF%ld.pdf",(long)sender.tag]];
        NSLog(@"PDF path: %@",filePath);
        [data writeToFile:filePath atomically:YES];

    });

}

正在使用以下代码查看文件

-(void)viewAction:(UIButton *)sender
{
    NSArray *searchPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentPath = [searchPaths objectAtIndex:0];
    NSURL *url =  [NSURL fileURLWithPath:[documentPath stringByAppendingPathComponent:[NSString stringWithFormat:@"myPDF%ld.pdf",(long)sender.tag]]];
    if (url) {
        // Initialize Document Interaction Controller
        _documentInteractionController = [UIDocumentInteractionController interactionControllerWithURL:url];

        // Configure Document Interaction Controller
        [_documentInteractionController setDelegate:self];

        // Preview PDF
        [_documentInteractionController presentPreviewAnimated:YES];
    }
}

现在我想把每个单元格的进度条对应于每个pdf文件进行下载..下载文件后...我想将按钮名称“下载”更改为“查看”并更改相应的动作......还有一件事，我应该能够在重新打开应用程序后查看该文件，因为它已经下载了..

Answer 1

对于进度条更新，请使用NSURLConnection委托，

示例：

 (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
      //here you will get total length 
      totalLength = [response expectedContentLength];
    }

    (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data 
    {
      // here calculate the downloaded length
      [self.pdfData appendData:data];
      //calculate downloaded percent
      progress = ([self.pdfData length] * 100) / totalLength;
      //and update the progress bar
    }

    (void)connectionDidFinishLoading:(NSURLConnection *)connection 
    {
      //save file here
      //flip the corresponding button to view here
    }

要查看下载的pdf文件，请检查文件是否已下载

示例：

if ([[NSFileManager defaultManager] fileExistsAtPath:filePath])
{
  // show the view button
}
else
  //start download

Answer 2

要使用NSURLconnection计算下载进度，请使用以下委托功能。

-(void) connection:(NSURLConnection *) connection
        didReceiveResponse:(NSURLResponse *) response
        {
            //In this function you will get the total size of PDF data you are receiving
            fTotalSize=(float)[response expectedContentLength];

            if(!datWebServiceData)
        datWebServiceData =[[NSMutableData alloc]init];

           //datWebServiceData = [[NSMutableData data] retain];
           [datWebServiceData setLength: 0];
        }

-(void) connection:(NSURLConnection *) connection
        didReceiveData:(NSData *) data
       {
         //Here calculate the progress
        float val=(((float) [datWebServiceData length] / (float) fTotalSize))*100;

        lblProgress.text=[NSString stringWithFormat:@"%0.0f%%",val];
       }

lblProgress.text将显示下载进度，datWebServiceData是NSData，它将包含PDF的全部数据。

现在要显示每个单元格的进度，请在NSMutableArray中保存连接对象。然后检查委托的连接对象和数组中的所有连接异议，如果它们匹配则接受数组索引，然后相应地更新该单元的条目。

Answer 3

首先创建UIButton的属性，如下所示 -

@property (strong,nonatomic) IBOutlet UIButton *btn;

然后进行连接。同样在viewDidLoad方法中执行如下操作 -

[_btn setTitle:@"DOWNLOADING" forState:UIControlStateNormal];

[_btn addTarget:self action:@selector(buttonClicked:) forControlEvents:UIControlEventTouchUpInside];

因此，在您的startDownloadFile方法中添加以下内容 -

    NSLog(@"PDF path: %@",filePath);
    [data writeToFile:filePath atomically:YES];
    /* ADD BELOW LINE */
    [_btn setTitle:@"VIEW" forState:UIControlStateNormal];

然后对于buttonClicked：方法为 -

-(void)buttonClicked:(UIButton *)sender
{
  if([sender.titleLabel.text isEqualToString:@"VIEW"])
  {
    /* Now as title is VIEW so call viewAction method */
    [self viewAction:sender]
  }
  else
  {
    /*When tapped in DOWNLOADING mode nothing will happen */
  }
}

下载pdf文件的进度条

3 个答案: