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:

EventListener, FiresFormEvents, HasWidgets, com.google.gwt.user.client.ui.impl.FormPanelImplHost

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:

• TextBox
• PasswordTextBox
• RadioButton
• CheckBox
• TextArea
• ListBox
• FileUpload
• Hidden

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 ClickListener() {
      public void onClick(Widget sender) {
        form.submit();
      }
    }));

    // Add an event handler to the form.
    form.addFormHandler(new FormHandler() {
      public void onSubmit(FormSubmitEvent 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.setCancelled(true);
        }
      }

      public void onSubmitComplete(FormSubmitCompleteEvent 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 Summary

static java.lang.String	ENCODING_MULTIPART Used with setEncoding(String) to specify that the form will be submitted using MIME encoding (necessary for FileUpload to work properly).
static java.lang.String	ENCODING_URLENCODED Used with setEncoding(String) to specify that the form will be submitted using traditional URL encoding.
static java.lang.String	METHOD_GET Used with setMethod(String) to specify that the form will be submitted using an HTTP GET request.
static java.lang.String	METHOD_POST Used with setMethod(String) to specify that the form will be submitted using an HTTP POST request (necessary for FileUpload to work properly).

Constructor Summary

FormPanel()
Creates a new FormPanel.

FormPanel(NamedFrame frameTarget)
Creates a FormPanel that targets a NamedFrame.

FormPanel(java.lang.String target)
Creates a new FormPanel.

Method Summary

void	addFormHandler(FormHandler handler) Adds a handler interface to receive click events.
java.lang.String	getAction() Gets the 'action' associated with this form.
java.lang.String	getEncoding() Gets the encoding used for submitting this form.
java.lang.String	getMethod() Gets the HTTP method used for submitting this form.
java.lang.String	getTarget() Gets the form's 'target'.
protected void	onAttach() This method is called when a widget is attached to the browser's document.
protected void	onDetach() This method is called when a widget is detached from the browser's document.
boolean	onFormSubmit()
void	onFrameLoad()
void	removeFormHandler(FormHandler handler) Removes a previously added handler interface.
void	setAction(java.lang.String url) Sets the 'action' associated with this form.
void	setEncoding(java.lang.String encodingType) Sets the encoding used for submitting this form.
void	setMethod(java.lang.String method) Sets the HTTP method used for submitting this form.
void	submit() Submits the form.

Methods inherited from class com.google.gwt.user.client.ui.SimplePanel

add, getContainerElement, getWidget, iterator, remove, setWidget

Methods inherited from class com.google.gwt.user.client.ui.Panel

adopt, adopt, clear, disown, doAttachChildren, doDetachChildren, onLoad, onUnload, orphan

Methods inherited from class com.google.gwt.user.client.ui.Widget

getParent, isAttached, onBrowserEvent, removeFromParent, setElement

Methods inherited from class com.google.gwt.user.client.ui.UIObject

addStyleDependentName, addStyleName, getAbsoluteLeft, getAbsoluteTop, getElement, getOffsetHeight, getOffsetWidth, getStyleElement, getStyleName, getStyleName, getStylePrimaryName, getStylePrimaryName, getTitle, isVisible, isVisible, removeStyleDependentName, removeStyleName, setHeight, setPixelSize, setSize, setStyleName, setStyleName, setStyleName, setStylePrimaryName, setStylePrimaryName, setTitle, setVisible, setVisible, setWidth, sinkEvents, toString, unsinkEvents

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

ENCODING_MULTIPART

public static final java.lang.String ENCODING_MULTIPART

Used with setEncoding(String) to specify that the form will be submitted using MIME encoding (necessary for FileUpload to work properly).

See Also:

Constant Field Values

ENCODING_URLENCODED

public static final java.lang.String ENCODING_URLENCODED

Used with setEncoding(String) to specify that the form will be submitted using traditional URL encoding.

See Also:

Constant Field Values

METHOD_GET

public static final java.lang.String METHOD_GET

Used with setMethod(String) to specify that the form will be submitted using an HTTP GET request.

See Also:

Constant Field Values

METHOD_POST

public static final java.lang.String METHOD_POST

Used with setMethod(String) to specify that the form will be submitted using an HTTP POST request (necessary for FileUpload to work properly).

See Also:

Constant Field Values

Constructor Detail

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 FormHandler.

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 FormHandler.onSubmitComplete(FormSubmitCompleteEvent) 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 onFormSubmit event.

Parameters:

frameTarget - the NamedFrame to be targetted

FormPanel

public FormPanel(java.lang.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 onFormSubmit 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

Method Detail

addFormHandler

public void addFormHandler(FormHandler handler)

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

getAction

public java.lang.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 java.lang.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 java.lang.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 java.lang.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()

Specified by:

onFormSubmit in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost

onFrameLoad

public void onFrameLoad()

Specified by:

onFrameLoad in interface com.google.gwt.user.client.ui.impl.FormPanelImplHost

removeFormHandler

public void removeFormHandler(FormHandler handler)

Description copied from interface: FiresFormEvents

Removes a previously added handler interface.

Specified by:

removeFormHandler in interface FiresFormEvents

Parameters:

handler - the handler interface to remove

setAction

public void setAction(java.lang.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

setEncoding

public void setEncoding(java.lang.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(java.lang.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.

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

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.

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