ZK Developer's Reference/UI Patterns/Event Threads/File Upload

File Upload with Servlet Thread

When the event thread is disable (default), it is recommended to use Button, Toolbarbutton or Menuitem with upload="true" instead. For example,

<zk>
	<zscript>
	void upload(UploadEvent event) {
		org.zkoss.util.media.Media media = event.getMedia();
		if (media instanceof org.zkoss.image.Image) {
			org.zkoss.zul.Image image = new org.zkoss.zul.Image();
			image.setContent( (org.zkoss.image.Image) media);
			image.setParent(pics);
		} else {
			Messagebox.show("Not an image: "+media, "Error", Messagebox.OK, Messagebox.ERROR);
		}
	}
	</zscript>
	<button label="Upload" upload="true" onUpload="upload(event)"/>
	<toolbarbutton label="Upload" upload="true" onUpload="upload(event)"/>
	<vbox id="pics" />
</zk>

If you prefer to use a dialog (Fileupload.get()), please take a look at ZK Component Reference: Fileupload for more inormation.

File Upload with Event Thread

If the event thread is disabled, the developer can use Button or Toolbarbutton with upload="true" instead. They behave the same no matter if the event thread is disabled or not.

However, if the event thread is enabled, you can get uploaded Media returned by Fileupload.get() and other overloadded static methods.

<zk>
	<button label="Upload">
	<attribute name="onClick">{
		org.zkoss.util.media.Media[] media = Fileupload.get(-1);
		if (media != null) {
			for (int i = 0; i < media.length; i++) {
				if (media[i] instanceof org.zkoss.image.Image) {
					org.zkoss.zul.Image image = new org.zkoss.zul.Image();
					image.setContent(media[i]);
					image.setParent(pics);
				} else {
					Messagebox.show("Not an image: "+media[i], "Error", Messagebox.OK, Messagebox.ERROR);
					break; //not to show too many errors
				}
			}
		}
	}</attribute>
	</button>
	<vbox id="pics" />
</zk>

As shown, Fileupload.get(int) won't return until an end user uploads the files (and/or closes the dialog).