Package com.google.gwt.user.client.ui

Class FormPanel

java.lang.Object
com.google.gwt.user.client.ui.UIObject
com.google.gwt.user.client.ui.Widget
com.google.gwt.user.client.ui.Panel
com.google.gwt.user.client.ui.SimplePanel
com.google.gwt.user.client.ui.FormPanel
All Implemented Interfaces:
HasAttachHandlers, HasHandlers, EventListener, AcceptsOneWidget, FiresFormEvents, HasOneWidget, HasVisibility, HasWidgets, HasWidgets.ForIsWidget, com.google.gwt.user.client.ui.impl.FormPanelImplHost, IsWidget, Iterable<Widget>
public class FormPanel extends SimplePanel implements FiresFormEvents, com.google.gwt.user.client.ui.impl.FormPanelImplHost
A panel that wraps its contents in an HTML <FORM> element.

This panel can be used to achieve interoperability with servers that accept traditional HTML form encoding. The following widgets (those that implement HasName) will be submitted to the server if they are contained within this panel:

In particular, FileUpload is only useful when used within a FormPanel, because the browser will only upload files using form submission.

Example

public class FormPanelExample implements EntryPoint {

  public void onModuleLoad() {
    // Create a FormPanel and point it at a service.
    final FormPanel form = new FormPanel();
    form.setAction("/myFormHandler");

    // Because we're going to add a FileUpload widget, we'll need to set the
    // form to use the POST method, and multipart MIME encoding.
    form.setEncoding(FormPanel.ENCODING_MULTIPART);
    form.setMethod(FormPanel.METHOD_POST);

    // Create a panel to hold all of the form widgets.
    VerticalPanel panel = new VerticalPanel();
    form.setWidget(panel);

    // Create a TextBox, giving it a name so that it will be submitted.
    final TextBox tb = new TextBox();
    tb.setName("textBoxFormElement");
    panel.add(tb);

    // Create a ListBox, giving it a name and some values to be associated with
    // its options.
    ListBox lb = new ListBox();
    lb.setName("listBoxFormElement");
    lb.addItem("foo", "fooValue");
    lb.addItem("bar", "barValue");
    lb.addItem("baz", "bazValue");
    panel.add(lb);

    // Create a FileUpload widget.
    FileUpload upload = new FileUpload();
    upload.setName("uploadFormElement");
    panel.add(upload);

    // Add a 'submit' button.
    panel.add(new Button("Submit", new ClickHandler() {
      public void onClick(ClickEvent event) {
        form.submit();
      }
    }));

    // Add an event handler to the form.
    form.addSubmitHandler(new FormPanel.SubmitHandler() {
      public void onSubmit(SubmitEvent event) {
        // This event is fired just before the form is submitted. We can take
        // this opportunity to perform validation.
        if (tb.getText().length() == 0) {
          Window.alert("The text box must not be empty");
          event.cancel();
        }
      }
    });
    form.addSubmitCompleteHandler(new FormPanel.SubmitCompleteHandler() {
      public void onSubmitComplete(SubmitCompleteEvent event) {
        // When the form submission is successfully completed, this event is
        // fired. Assuming the service returned a response of type text/html,
        // we can get the result text here (see the FormPanel documentation for
        // further explanation).
        Window.alert(event.getResults());
      }
    });

    RootPanel.get().add(form);
  }
}