How to start a file download in vaadin without button?

Question

I know that it is really easy to create a FileDownloader and call extend with a Button. But how do I start a download without the Button?

Answer 1

Here is my work-around. It works like a charm for me. Hope it will help you.

1. Create a button and hide it by Css (NOT by code: button.setInvisible(false))

   final Button downloadInvisibleButton = new Button();
   downloadInvisibleButton.setId("DownloadButtonId");
   downloadInvisibleButton.addStyleName("InvisibleButton");
   

   In your theme, add this rule to hide the downloadInvisibleButton:

   .InvisibleButton {
       display: none;
   }
   

2. When the user clicks on menuItem: extend the fileDownloader to the downloadInvisibleButton, then simulate the click on the downloadInvisibleButton by JavaScript.

   menuBar.addItem("Download", new MenuBar.Command() {
     @Override
     public void menuSelected(MenuBar.MenuItem selectedItem) {
       FileDownloader fileDownloader = new FileDownloader(...);
       fileDownloader.extend(downloadInvisibleButton);
       //Simulate the click on downloadInvisibleButton by JavaScript
       Page.getCurrent().getJavaScript()
          .execute("document.getElementById('DownloadButtonId').click();");
     }
   });