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);
  }
}

  • Field Details

  • Constructor Details

    • FormPanel

      public FormPanel()
      Creates a new FormPanel. When created using this constructor, it will be submitted to a hidden <iframe> element, and the results of the submission made available via FormPanel.SubmitCompleteHandler.

      The back-end server is expected to respond with a content-type of 'text/html', meaning that the text returned will be treated as HTML. If any other content-type is specified by the server, then the result HTML sent in the onFormSubmit event will be unpredictable across browsers, and the onSubmitComplete event may not fire at all.

      Tip:
      The initial implementation of FormPanel specified that the server respond with a content-type of 'text/plain'. This has been intentionally changed to specify 'text/html' because 'text/plain' cannot be made to work properly on all browsers.

    • FormPanel

      public FormPanel(NamedFrame frameTarget)
      Creates a FormPanel that targets a NamedFrame. The target frame is not physically attached to the form, and must therefore still be added to a panel elsewhere.

      When the FormPanel targets an external frame in this way, it will not fire the FormSubmitComplete event.

      Parameters:
      frameTarget - the NamedFrame to be targetted

    • FormPanel

      public FormPanel(String target)
      Creates a new FormPanel. When created using this constructor, it will be submitted either by replacing the current page, or to the named <iframe>.

      When the FormPanel targets an external frame in this way, it will not fire the FormSubmitComplete event.

      Parameters:
      target - the name of the <iframe> to receive the results of the submission, or null to specify that the current page be replaced

    • FormPanel

      protected FormPanel(Element element)
      This constructor may be used by subclasses to explicitly use an existing element. This element must be a <form> element.

      The specified form element's target attribute will not be set, and the FormSubmitCompleteEvent will not be fired.

      Parameters:
      element - the element to be used

    • FormPanel

      protected FormPanel(Element element, boolean createIFrame)
      This constructor may be used by subclasses to explicitly use an existing element. This element must be a <form> element.

      If the createIFrame parameter is set to true, then the wrapped form's target attribute will be set to a hidden iframe. If not, the form's target will be left alone, and the FormSubmitComplete event will not be fired.

      Parameters:
      element - the element to be used
      createIFrame - true to create an <iframe> element that will be targeted by this form

  • Method Details

    • wrap

      public static FormPanel wrap(Element element)
      Creates a FormPanel that wraps an existing <form> element. This element must already be attached to the document. If the element is removed from the document, you must call Widget.removeFromParent().

      The specified form element's target attribute will not be set, and the FormSubmitCompleteEvent will not be fired.

      Parameters:
      element - the element to be wrapped

    • wrap

      public static FormPanel wrap(Element element, boolean createIFrame)
      Creates a FormPanel that wraps an existing <form> element. This element must already be attached to the document. If the element is removed from the document, you must call Widget.removeFromParent().

      If the createIFrame parameter is set to true, then the wrapped form's target attribute will be set to a hidden iframe. If not, the form's target will be left alone, and the FormSubmitComplete event will not be fired.

      Parameters:
      element - the element to be wrapped
      createIFrame - true to create an <iframe> element that will be targeted by this form

    • addFormHandler

      @Deprecated public void addFormHandler(FormHandler handler)
      Deprecated.
      Use addSubmitCompleteHandler(com.google.gwt.user.client.ui.FormPanel.SubmitCompleteHandler) and addSubmitHandler(com.google.gwt.user.client.ui.FormPanel.SubmitHandler) instead
      Description copied from interface: FiresFormEvents
      Adds a handler interface to receive click events.
      Specified by:
      addFormHandler in interface FiresFormEvents
      Parameters:
      handler - the handler interface to add

    • addSubmitCompleteHandler

      public HandlerRegistration addSubmitCompleteHandler(FormPanel.SubmitCompleteHandler handler)
      Adds a FormPanel.SubmitCompleteEvent handler.
      Parameters:
      handler - the handler
      Returns:
      the handler registration used to remove the handler

    • addSubmitHandler

      public HandlerRegistration addSubmitHandler(FormPanel.SubmitHandler handler)
      Adds a FormPanel.SubmitEvent handler.
      Parameters:
      handler - the handler
      Returns:
      the handler registration used to remove the handler

    • getAction

      public String getAction()
      Gets the 'action' associated with this form. This is the URL to which it will be submitted.
      Returns:
      the form's action

    • getEncoding

      public String getEncoding()
      Gets the encoding used for submitting this form. This should be either ENCODING_MULTIPART or ENCODING_URLENCODED.
      Returns:
      the form's encoding

    • getMethod

      public String getMethod()
      Gets the HTTP method used for submitting this form. This should be either METHOD_GET or METHOD_POST.
      Returns:
      the form's method

    • getTarget

      public String getTarget()
      Gets the form's 'target'. This is the name of the NamedFrame that will receive the results of submission, or null if none has been specified.
      Returns:
      the form's target.

    • onFormSubmit

      public boolean onFormSubmit()
      Fired when a form is submitted.
      Specified by:
      onFormSubmit in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost
      Returns:
      true if the form is submitted, false if canceled

    • onFrameLoad

      public void onFrameLoad()
      Description copied from interface: com.google.gwt.user.client.ui.impl.FormPanelImplHost
      Called when the target frame is done loading.
      Specified by:
      onFrameLoad in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost

    • removeFormHandler

      @Deprecated public void removeFormHandler(FormHandler handler)
      Deprecated.
      Use the HandlerRegistration.removeHandler() method on the object returned by and add*Handler method instead
      Description copied from interface: FiresFormEvents
      Removes a previously added handler interface.
      Specified by:
      removeFormHandler in interface FiresFormEvents
      Parameters:
      handler - the handler interface to remove

    • reset

      public void reset()
      Resets the form, clearing all fields.

    • setAction

      public void setAction(String url)
      Sets the 'action' associated with this form. This is the URL to which it will be submitted.
      Parameters:
      url - the form's action

    • setAction

      public void setAction(SafeUri url)
      Sets the 'action' associated with this form. This is the URL to which it will be submitted.
      Parameters:
      url - the form's action

    • setEncoding

      public void setEncoding(String encodingType)
      Sets the encoding used for submitting this form. This should be either ENCODING_MULTIPART or ENCODING_URLENCODED.
      Parameters:
      encodingType - the form's encoding

    • setMethod

      public void setMethod(String method)
      Sets the HTTP method used for submitting this form. This should be either METHOD_GET or METHOD_POST.
      Parameters:
      method - the form's method

    • submit

      public void submit()
      Submits the form.

      The FormPanel must not be detached (i.e. removed from its parent or otherwise disconnected from a RootPanel) until the submission is complete. Otherwise, notification of submission will fail.

    • onAttach

      protected void onAttach()
      Description copied from class: Widget

      This method is called when a widget is attached to the browser's document. To receive notification after a Widget has been added to the document, override the Widget.onLoad() method or use Widget.addAttachHandler(com.google.gwt.event.logical.shared.AttachEvent.Handler).

      It is strongly recommended that you override Widget.onLoad() or Widget.doAttachChildren() instead of this method to avoid inconsistencies between logical and physical attachment states.

      Subclasses that override this method must call super.onAttach() to ensure that the Widget has been attached to its underlying Element.

      Overrides:
      onAttach in class Widget
      See Also:

    • onDetach

      protected void onDetach()
      Description copied from class: Widget

      This method is called when a widget is detached from the browser's document. To receive notification before a Widget is removed from the document, override the Widget.onUnload() method or use Widget.addAttachHandler(com.google.gwt.event.logical.shared.AttachEvent.Handler).

      It is strongly recommended that you override Widget.onUnload() or Widget.doDetachChildren() instead of this method to avoid inconsistencies between logical and physical attachment states.

      Subclasses that override this method must call super.onDetach() to ensure that the Widget has been detached from the underlying Element. Failure to do so will result in application memory leaks due to circular references between DOM Elements and JavaScript objects.

      Overrides:
      onDetach in class Widget
      See Also:

    • getSynthesizedIFrame

      Element getSynthesizedIFrame()