Applets are programs that can be downloaded and run by a Java-enabled web
browser. These programs are generally small and specialized. An
applet runs in a web page on a client system, within bounds specified by the
page markup. A Java applet operates within constraints that provide
security from remote system intrusion.
You can compose and test an applet in the Visual Composition Editor.
To run an applet in a web page, export the applet class and edit the web page
source file to include the applet.
VisualAge provides applet beans from the
com.sun.java.swing and
java.applet packages, as well as others. Although
Swing and AWT beans can be mixed, it is inadvisable.
- Create one of the following applet beans:
Bean
| Description
|
JApplet or Applet
| A program that can run in a compatible web browser
|
- Creating an applet bean
- Create an applet as a new composite bean. You can create the bean
in any of the following ways:
- From the Quick Start window. Select Quick Start from the
File pull-down menu to open the Quick Start window. Select
Basic in the left pane, Create Applet in the right pane,
and the OK button to open the SmartGuide - Create Applet
window. See the related task topic on Creating an applet for
details.
- From the Create Applet tool bar button. Select the
button on the tool bar to open the SmartGuide - Create Applet
window. Specify one of the applet beans as the superclass for your
applet, and request to compose the class visually. See the related task
topic on Creating an applet for details.
- From the Create Class tool bar button. Select the
button on the tool bar to open the SmartGuide - Create Class
window. Specify one of the applet beans as the superclass for your
applet, and request to compose the class visually. See the related task
topic on Creating a class for details.
- Compose the user interface and logic for the applet. Add and
arrange visual components, add nonvisual beans, and connect them to establish
functional relationships.
- Accessing a JApplet bean in the Visual Composition Editor
- When you create a JApplet bean, a content pane is also added in which to
place other components. With the exception of a JMenuBar, user
interface components are added to the content pane. As a result, the
content pane completely covers the Japplet bean in the Visual Composition
Editor. To access the JApplet bean, open the Beans List.
- Resizing or moving a JApplet bean in the Visual Composition Editor
- Select the JApplet bean in the Beans List. Then, you can resize or
move the JApplet in the Visual Composition Editor. If you try to select
the JApplet bean in the Visual Composition Editor, you will select its content
pane instead.
- Replacing the content pane for a JApplet bean
- To replace the content pane, delete it and add another container
component. When you delete the content pane, a warning is displayed
indicating that the content pane is missing. If you save the bean
without adding another content pane, a JPanel bean is used.
- Arranging beans in an applet
- Use either of the following methods:
- Use a layout manager to control size and position of beans within the
applet or applet content pane.
- Without using a layout manager, place beans approximately where you want
them and use visual composition tools to align them.
- Accessing the applet context
- The applet context represents the environment in which an applet is
running. It provides methods to get an image from a URL, to get an
audio clip from a URL, to find other applets within the document, and to show
a document at another URL. To access these applet context methods, tear
off the appletContext property of the Applet or JApplet
bean. Access a JApplet bean in the Beans List.
- Accessing the document or applet URL
- To get the URL of the HTML file that the applet is running in, connect to
the documentBase property or the getDocumentBase method
of the Applet or JApplet bean. To get the URL of the applet, connect to
the codeBase property or the getCodeBase method of the
Applet or JApplet bean.
- Providing information about the applet
- To define information about your applet, edit the getAppletInfo
method on the Methods page. To get the applet information for an About
dialog, connect to the appletInfo property or the
getAppletInfo method of the Applet or JApplet bean.
- Test the applet. You can run the applet from the Visual Composition
Editor. This makes it easy to iteratively modify and test the applet
while you compose it.
- Testing an applet from the Visual Composition Editor
- Do either of the following to test the applet:
- Select the
button on the tool bar.
- From the Bean pull-down menu, select Run, then
either In Applet Viewer or Run main.
VisualAge performs the following steps:
- Saves the edit description of the bean
- Generates source code
- Compiles the class
- Runs the applet
- Export the applet class and related resources from VisualAge.
- Exporting an applet class
- Select the applet class in the Workbench window. Then, select
Export from the File menu to open the SmartGuide -
Export window. See the related task topic on Exporting a class for
details.
- Edit your web page source file to add the applet. Specify the
applet at the location in your page markup where you want the applet to
run. If you had VisualAge generate an HTML file when you exported the
applet, you need to edit the source to specify attributes for the
<applet> tag.
- Adding an applet in an HTML file
- Use the <applet> tag to identify the applet class and to
specify the dimensions of the bounding rectangle in which the applet is to
run. The following example includes an applet named MyApplet.
The applet is run in a rectangle that is 100 pixels wide and 80 pixels
high.
<applet code="MyApplet.class" width=100 height=80></applet>
See books documenting HTML for other attributes that can be specified on
the Applet tag.
For examples, see the BookmarkList class in the
com.ibm.ivj.examples.vc.swing.bookmarklist
and
com.ibm.ivj.examples.vc.bookmarklist
packages. These examples are shipped in the IBM Java Examples
project.
Working with Beans Visually
Using VisualAge Beans in Visual Composition
Creating an applet
Creating a class
Exporting a class
Adding the IBM Java Examples project
Applet Beans
BookmarkList Sample
