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GWT - ScrollPanel Widget
Introduction
The ScrollPanel widget represents a simple panel that wraps its contents in a scrollable area.
Class Declaration
Following is the declaration for com.google.gwt.user.client.ui.ScrollPanel class −
public class ScrollPanel extends SimplePanel implements SourcesScrollEvents, HasScrollHandlers, RequiresResize, ProvidesResize
Class Constructors
Sr.No. | Constructor & Description |
---|---|
1 |
ScrollPanel() Creates an empty scroll panel. |
2 |
ScrollPanel(Widget child) Creates a new scroll panel with the given child widget. |
Class Methods
Sr.No. | Function name & Description |
---|---|
1 |
HandlerRegistration addScrollHandler(ScrollHandler handler) Adds a ScrollEvent handler. |
2 |
void addScrollListener(ScrollListener listener) Deprecated. Use addScrollHandler(com.google.gwt.event.dom.client.ScrollHandler) instead |
3 |
void ensureVisible(UIObject item) Ensures that the specified item is visible, by adjusting the panel's scroll position. |
4 | protected Element getContainerElement() Override this method to specify that an element other than the root element be the container for the panel's child widget. |
5 | int getHorizontalScrollPosition() Gets the horizontal scroll position. |
6 |
int getScrollPosition() Gets the vertical scroll position. |
7 |
void onResize() This method must be called whenever the implementor's size has been modified. |
8 |
void removeScrollListener(ScrollListener listener) Deprecated. Use the HandlerRegistration.removeHandler() method on the object returned by addScrollHandler(com.google.gwt.event.dom.client.ScrollHandler) instead |
9 |
void scrollToBottom() Scroll to the bottom of this panel. |
10 |
void scrollToLeft() Scroll to the far left of this panel. |
11 |
void scrollToRight() Scroll to the far right of this panel. |
12 |
void scrollToTop() Scroll to the top of this panel. |
13 |
void setAlwaysShowScrollBars(boolean alwaysShow) Sets whether this panel always shows its scroll bars, or only when necessary. |
14 |
void setHeight(java.lang.String height) Sets the object's height. |
15 |
void setHorizontalScrollPosition(int position) Sets the horizontal scroll position. |
16 |
void setScrollPosition(int position) Sets the vertical scroll position. |
17 |
void setSize(java.lang.String width, java.lang.String height) Sets the object's size. |
18 |
void setWidth(java.lang.String width) Sets the object's width. |
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
ScrollPanel Widget Example
This example will take you through simple steps to show usage of a ScrollPanel 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>ScrollPanel 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 ScrollPanel 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.HTML; import com.google.gwt.user.client.ui.RootPanel; import com.google.gwt.user.client.ui.ScrollPanel; public class HelloWorld implements EntryPoint { public void onModuleLoad() { // Create scrollable text HTML contents = new HTML("This is a ScrollPanel." +" 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." +" Here's quite a bit more meaningless text that will serve primarily" +" 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!"); //create scrollpanel with content ScrollPanel scrollPanel = new ScrollPanel(contents); scrollPanel.setSize("400px", "100px"); DecoratorPanel decoratorPanel = new DecoratorPanel(); decoratorPanel.add(scrollPanel); // 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 −