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GWT - Hidden Widget
Introduction
The Hidden widget represents a hidden field in an HTML form.
Class Declaration
Following is the declaration for com.google.gwt.user.client.ui.Hidden class −
public class Hidden extends Widget implements HasName
Class Constructors
Sr.No. | Constructor & Description |
---|---|
1 |
Hidden() Constructor for Hidden. |
2 |
Hidden(Element element) This constructor may be used by subclasses to explicitly use an existing element. |
3 |
Hidden(java.lang.String name) Constructor for Hidden. |
4 |
Hidden(java.lang.String name, java.lang.String value) Constructor for Hidden. |
Class Methods
Sr.No. | Function name & Description |
---|---|
1 |
java.lang.String getDefaultValue() Gets the default value of the hidden field. |
2 |
java.lang.String getID() Gets the id of the hidden field. |
3 |
java.lang.String getName() Gets the name of the hidden field. |
4 |
java.lang.String getValue() Gets the value of the hidden field. |
5 |
void setDefaultValue(java.lang.String defaultValue) Sets the default value of the hidden field. |
6 |
void setID(java.lang.String id) Sets the id of the hidden field. |
7 |
void setName(java.lang.String name) Sets the name of the hidden field. |
8 |
void setValue(java.lang.String value) Sets the value of the hidden field. |
9 |
static Hidden wrap(Element element) Creates a Hidden widget that wraps an existing <input type='hidden'> 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
java.lang.Object
Hidden Widget Example
This example will take you through simple steps to show usage of a Hidden 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>Hidden 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 Hidden 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.Hidden; 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 textboxes final TextBox textBox = new TextBox(); textBox.setWidth("275"); Button button1 = new Button("Set Value of Hidden Input"); Button button2 = new Button("Get Value of Hidden Input"); final Hidden hidden = new Hidden(); button1.addClickHandler(new ClickHandler() { @Override public void onClick(ClickEvent event) { hidden.setValue(textBox.getValue()); Window.alert("Value of Hidden Widget Updated!"); } }); button2.addClickHandler(new ClickHandler() { @Override public void onClick(ClickEvent event) { Window.alert("Value of Hidden Widget: " + hidden.getValue()); } }); // Add widgets to the root panel. VerticalPanel panel = new VerticalPanel(); panel.setSpacing(10); panel.add(textBox); panel.add(button1); panel.add(hidden); panel.add(button2); RootPanel.get("gwtContainer").add(panel); } }
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 −