GWT - HTMLPanel Widget


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Introduction

The HTMLPanel widget represents a panel that contains HTML, and which can attach child widgets to identified elements within that HTML.

Class Declaration

Following is the declaration for com.google.gwt.user.client.ui.HTMLPanel class −

public class HTMLPanel
   extends ComplexPanel

Class Constructors

Sr.No. Constructor & Description
1

HTMLPanel(SafeHtml safeHtml)

Initializes the panel's HTML from a given SafeHtml object.

2

HTMLPanel(java.lang.String html)

Creates an HTML panel with the specified HTML contents inside a DIV element.

3

HTMLPanel(java.lang.String tag, java.lang.String html)

Creates an HTML panel whose root element has the given tag, and with the specified HTML contents.

Class Methods

Sr.No. Function name & Description
1

void add(Widget widget, Element elem)

Adds a child widget to the panel, contained within an HTML element.

2

void add(Widget widget, java.lang.String id)

Adds a child widget to the panel, contained within the HTML element specified by a given id.

3

void addAndReplaceElement(Widget widget, Element toReplace)

Adds a child widget to the panel, replacing the HTML element.

4

void addAndReplaceElement(Widget widget, java.lang.String id)

Adds a child widget to the panel, replacing the HTML element specified by a given id.

5

static java.lang.String createUniqueId()

A helper method for creating unique IDs for elements within dynamically- generated HTML.

6

Element getElementById(java.lang.String id)

Finds an element within this panel by its id.

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.ComplexPanel

  • java.lang.Object

HTMLPanel Widget Example

This example will take you through simple steps to show usage of a HTMLPanel 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>HTMLPanel 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 HTMLPanel widget.

package com.tutorialspoint.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.user.client.ui.DecoratorPanel;
import com.google.gwt.user.client.ui.HTMLPanel;
import com.google.gwt.user.client.ui.RootPanel;

public class HelloWorld implements EntryPoint {
   public void onModuleLoad() {
      String htmlString = "This is a <b>HTMLPanel</b> containing"
         +" html contents. "
         +" <i>By putting some fairly large contents in the middle"
         +" and setting its size explicitly, it becomes a scrollable area"
         +" within the page, but without requiring the use of an IFRAME.</i>"
         +" <u>Here's quite a bit more meaningless text that will serve"
         +" to make this thing scroll off the bottom of its visible area."
         +" Otherwise, you might have to make it really, really"
         +" small in order to see the nifty scroll bars!</u>";

      HTMLPanel htmlPanel = new HTMLPanel(htmlString);

      DecoratorPanel panel = new DecoratorPanel();
      panel.add(htmlPanel);

      // Add the widgets to the root panel.
      RootPanel.get().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 −

GWT HTMLPanel Widget
gwt_layout_panels.htm


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