我坚持FileDownloader重置扩展

Question

我们知道，我们必须与按钮延长FileDownloader能够下载文件。

//
Button downloadButton = new Button("download");

private void  updateFileForDownload(){
    ...       
    StreamResource sr = getFileStream();
    FileDownloader fileDownloader = new FileDownloader(sr);
    fileDownloader.extend(downloadButton);
    ...
}
private StreamResource getFileStream() {
    StreamResource.StreamSource source = () -> new ByteArrayInputStream(binderDocument.getBean().getFile());
    StreamResource resource = new StreamResource(source, binderDocument.getBean().getFilename());
    return resource;
}

我在我的应用程序的一些问题。如果我叫方法updateFileForDownload多个时间点击downloadButton获得多个文件。我需要重新扩展按钮或FileDownloader。我都尝试：

 downloadButton.removeExtension(fileDownloader);

在这里，我们得到

java.lang.IllegalArgumentException异常：该连接器是不适合在com.vaadin.server.AbstractClientConnector.removeExtension给定延伸的父（AbstractClientConnector.java:595）

fileDownloader.removeExtension(downloadButton); 

在这里，我们不能Apply按钮，扩展

如何重置FileDownloader的按钮？

Answer 1

您扩展下载

    fileDownloader.extend(download);

但尝试删除从fileDownloader扩展

 downloadButton.removeExtension(fileDownloader);

这是一个不匹配。 （假设是一个错字虽然。）

您可以删除按钮，然后创建一个新的按钮，新的下载，然后扩展这一点。有些分机不能被删除，虽然。

但是，你并不需要这一点。您只需更新StreamResource并没有触及绑定的。

一个更复杂的例子是从https://vaadin.com/docs/v8/framework/articles/LettingTheUserDownloadAFile.html的OnDemandDownloader

     /**
     * This specializes {@link FileDownloader} in a way, such that both the file name and content can be determined
     * on-demand, i.e. when the user has clicked the component.
     */
    public class OnDemandFileDownloader extends FileDownloader {

      /**
       * Provide both the {@link StreamSource} and the filename in an on-demand way.
       */
      public interface OnDemandStreamResource extends StreamSource {
        String getFilename ();
      }

      private static final long serialVersionUID = 1L;
      private final OnDemandStreamResource onDemandStreamResource;

      public OnDemandFileDownloader (OnDemandStreamResource onDemandStreamResource) {
        super(new StreamResource(onDemandStreamResource, ""));
        this.onDemandStreamResource = checkNotNull(onDemandStreamResource,
          "The given on-demand stream resource may never be null!");
      }

      @Override
      public boolean handleConnectorRequest (VaadinRequest request, VaadinResponse response, String path)
          throws IOException {
        getResource().setFilename(onDemandStreamResource.getFilename());
        return super.handleConnectorRequest(request, response, path);
      }

      private StreamResource getResource () {
        return (StreamResource) this.getResource("dl");
      }
    }