GWT FormPanel

This Panel deals with the elements of HTML FORM. In this panel, we can add any widget that would be wrapped inside HTML form element.

GWT FormPanel Class Declaration

Let's see the declaration of com.google.gwt.user.client.ui.FormPanel

GWT FormPanel Nested Classes

Class	Description
FormPanel.SubmitCompleteHandler	It handles for FormPanel.SubmitCompleteEvent events.
FormPanel.SubmitCompleteEvent	It is fired when a form has been submitted successfully.
FormPanel.SubmitEvent	It is fired when the form is submitte
FormPanel.SubmitHandler	It handles for FormPanel.SubmitEvent events.

GWT FormPanel Constructors

Constructor	Description
FormPanel()	It creates a new FormPanel.
FormPanel(Element element)	It is used by subclasses to explicitly use an existing element.
FormPanel(Element element, boolean createIFrame)	It is used by subclasses to explicitly use an existing element.
FormPanel(NamedFrame frameTarget)	It creates a FormPanel that targets a NamedFrame.
FormPanel(NamedFrame frameTarget)	It creates a FormPanel that targets a NamedFrame.
FormPanel(java.lang.String target)	It creates a new FormPanel that targets string as input.

GWT FormPanel Methods

Modifier and Types	Method	Description
void	addFormHandler(FormHandler handler)	It adds a form widget to the panel.
java.lang.String	getAction()	It gets the 'action' associated with this form.
java.lang.String	getEncoding()	It gets the encoding used for submitting this form.
java.lang.String	getMethod()	It gets the HTTP method used for submitting this form.
java.lang.String	getTarget()	It 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.
void	onFrameLoad()	It is called when the target frame is done loading.
void	setAction(SafeUri url)	It sets the 'action' associated with this form.
void	setAction(java.lang.String url)	It sets the 'action' associated with this form.
void	setEncoding(java.lang.String encodingType)	It sets the encoding used for submitting this form.
void	submit()	It submits the form.
static FormPanel	wrap(Element element)	It creates a FormPanel that wraps an existing element.
static FormPanel	wrap(Element element, boolean createIFrame)	It creates a FormPanel that wraps an existing element.

GWT FormPanel Example

//SampleFormPanel.java:

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.DecoratorPanel;
import com.google.gwt.user.client.ui.FileUpload;
import com.google.gwt.user.client.ui.FormPanel;
import com.google.gwt.user.client.ui.FormPanel.SubmitCompleteEvent;
import com.google.gwt.user.client.ui.FormPanel.SubmitEvent;
import com.google.gwt.user.client.ui.ListBox;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.VerticalPanel;

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");

    
    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("Item1", "Item1Value");
    lb.addItem("Item2", "Item2Value");
    lb.addItem("Item3", "Item3Value");
    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) {
 
        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) {
        
        Window.alert(event.getResults());
      }
    });

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

//SampleFormPanel.css:

body {
   text-align: center;
   font-family: verdana, sans-serif;
}

h1 {
   font-size: 2em;
   font-weight: bold;
   color: #777777;
   margin: 40px 0px 70px;
   text-align: center;
}

Output: