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GWT - FormPanel Widget
Introduction
The FormPanel widget represents a panel that wraps its contents in an HTML <FORM> element.
Class Declaration
Following is the declaration for com.google.gwt.user.client.ui.FormPanel class −
public class FormPanel extends SimplePanel implements FiresFormEvents, com.google.gwt.user.client.ui.impl.FormPanelImplHost
Class Constructors
Sr.No. | Constructor & Description |
---|---|
1 |
FormPanel() Creates a new FormPanel. |
2 |
protected FormPanel(Element element) This constructor may be used by subclasses to explicitly use an existing element. |
3 |
protected FormPanel(Element element, boolean createIFrame) This constructor may be used by subclasses to explicitly use an existing element. |
4 |
FormPanel(NamedFrame frameTarget) Creates a FormPanel that targets a NamedFrame. |
5 |
FormPanel(java.lang.String target) Creates a new FormPanel. |
Class Methods
Sr.No. | Function name & Description |
---|---|
1 |
void add Form Handler (FormHandler handler) Deprecated. Use add Submit Complete Handler (com.google.gwt.user.client.ui.Form Panel.Submit Complete Handler) and add Submit Handler (com.google.gwt.user.client.ui.Form Panel.Submit Handler) instead |
2 |
Handler Registration addSubmit Complete Handler (FormPanel.SubmitCompleteHandler handler) Adds a FormPanel.Submit Complete Event handler. |
3 |
HandlerRegistration addSubmitHandler(FormPanel.SubmitHandler handler) Adds a FormPanel.SubmitEvent handler. |
4 |
java.lang.String getAction() Gets the 'action' associated with this form. |
5 |
java.lang.String getEncoding() Gets the encoding used for submitting this form. |
6 |
java.lang.String getMethod() Gets the HTTP method used for submitting this form. |
7 |
java.lang.String getTarget() Gets the form's 'target'. |
8 |
protected void onAttach() This method is called when a widget is attached to the browser's document. |
9 |
protected void onDetach() This method is called when a widget is detached from the browser's document. |
10 |
boolean onFormSubmit() Fired when a form is submitted. |
11 |
void onFrameLoad() |
12 |
void removeFormHandler(FormHandler handler) Deprecated. Use the HandlerRegistration.removeHandler() method on the object returned by and add*Handler method instead |
13 |
void reset() Resets the form, clearing all fields. |
14 |
void setAction(java.lang.String url) Sets the 'action' associated with this form. |
15 |
void setEncoding(java.lang.String encodingType) Sets the encoding used for submitting this form. |
16 |
void setMethod(java.lang.String method) Sets the HTTP method used for submitting this form. |
17 |
void submit() Submits the form. |
18 |
static FormPanel wrap(Element element) Creates a FormPanel that wraps an existing <form> element. |
19 |
static FormPanel wrap(Element element, boolean createIFrame) Creates a FormPanel that wraps an existing <form> element. |
Methods Inherited
This class inherits methods from the following classes −
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
java.lang.Object
FormPanel Widget Example
This example will take you through simple steps to show usage of a FormPanel Widget in GWT. Follow the following steps to update the GWT application we created in GWT - Create Application chapter −
Step | Description |
---|---|
1 | Create a project with a name HelloWorld under a package com.tutorialspoint as explained in the GWT - Create Application chapter. |
2 | Modify HelloWorld.gwt.xml, HelloWorld.css, HelloWorld.html and HelloWorld.java as explained below. Keep rest of the files unchanged. |
3 | Compile and run the application to verify the result of the implemented logic. |
Following is the content of the modified module descriptor src/com.tutorialspoint/HelloWorld.gwt.xml.
<?xml version = "1.0" encoding = "UTF-8"?> <module rename-to = 'helloworld'> <!-- Inherit the core Web Toolkit stuff. --> <inherits name = 'com.google.gwt.user.User'/> <!-- Inherit the default GWT style sheet. --> <inherits name = 'com.google.gwt.user.theme.clean.Clean'/> <!-- Specify the app entry point class. --> <entry-point class = 'com.tutorialspoint.client.HelloWorld'/> <!-- Specify the paths for translatable code --> <source path = 'client'/> <source path = 'shared'/> </module>
Following is the content of the modified Style Sheet file war/HelloWorld.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; }
Following is the content of the modified HTML host file war/HelloWorld.html.
<html> <head> <title>Hello World</title> <link rel = "stylesheet" href = "HelloWorld.css"/> <script language = "javascript" src = "helloworld/helloworld.nocache.js"> </script> </head> <body> <h1>FormPanel Widget Demonstration</h1> <div id = "gwtContainer"></div> </body> </html>
Let us have following content of Java file src/com.tutorialspoint/HelloWorld.java which will demonstrate use of FormPanel widget.
package com.tutorialspoint.client; 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 HelloWorld 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(); panel.setSpacing(10); form.setWidget(panel); // Create a TextBox, giving it a name so that it will be submitted. final TextBox tb = new TextBox(); tb.setWidth("220"); 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", "item1"); lb.addItem("item2", "item2"); lb.addItem("item3", "item3"); lb.setWidth("220"); 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() { @Override public void onClick(ClickEvent event) { form.submit(); } })); // Add an event handler to the form. form.addSubmitHandler(new FormPanel.SubmitHandler() { @Override 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() { @Override 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 // here. Window.alert(event.getResults()); } }); DecoratorPanel decoratorPanel = new DecoratorPanel(); decoratorPanel.add(form); // Add the widgets to the root panel. RootPanel.get().add(decoratorPanel); } }
Once you are ready with all the changes done, let us compile and run the application in development mode as we did in GWT - Create Application chapter. If everything is fine with your application, this will produce following result −