How to use GWT fileupload?

I have some queries when trying to implement a fileupload widget in my application. After many tries, it just doesn't seem to work.

Hence, I tried getting working solutions to see if I can understand anything from there.

http://code.google.com/p/faculty-gwt/source/checkout

However, I tried uploading a file using this and it seems that I am getting error messages too. and what is that textbox and listbox suppose to do? It is meant for showing an example of validating an input bef开发者_如何学编程ore submitting?

Can someone guide me along to solve this? Thanks.

Never tried to use the link you provided, but this is what i did to use a a GWT FileUpload widget:

I built a File Upload widget using the uibinder:

<g:FormPanel ui:field="docForm">
    <g:FlowPanel ui:field="inputPane">
        /*other displayed info*/
        <g:FileUpload ui:field="DocPath"/>
        /*other displayed info*/
    </g:FlowPanel>
</g:FormPanel>

(Per the GWT api, FileUpload widgets can only be used from a FormPanel)

Make sure you set these in the FormPanel, otherwise you'll probably have issues:

    yourFormPanel.setEncoding(FormPanel.ENCODING_MULTIPART);
    yourFormPanel.setMethod(FormPanel.METHOD_POST);

That widget is dropped into my container page, then added to the display panel:

private FileUploadWidget createNewUploader(){
    FileUploadWidget uploader = new FileUploadWidget(/*my constructor params*/);

    uploader.addChangeHandler(new ChangeHandler() {         
        @Override
        public void onChange(ChangeEvent event) {
            DocPanel.add(createNewUploader());
        }
    });

    return uploader;
}

My OnChange event is so that I have a new, blank uploader available when i use the current one.

and when I'm ready to submit:

private void processUpload(FileUploadWidget upload, int id) {
    upload.setId(id);
    //Don't bother to submit an empty one.
    if (upload.IsFileSelected())
        upload.Submit();
}