public class Applet extends Panel
An applet is a small program that is intended not to be run on its own, but rather to be embedded inside another application.
The Applet
class must be the superclass of any applet that is to be embedded in a Web page or viewed by the Java Applet Viewer. The Applet
class provides a standard interface between applets and their environment.
Modifier and Type | Class and Description |
---|---|
protected class |
Applet.AccessibleApplet This class implements accessibility support for the |
Panel.AccessibleAWTPanel
Container.AccessibleAWTContainer
Component.AccessibleAWTComponent, Component.BaselineResizeBehavior, Component.BltBufferStrategy, Component.FlipBufferStrategy
BOTTOM_ALIGNMENT, CENTER_ALIGNMENT, LEFT_ALIGNMENT, RIGHT_ALIGNMENT, TOP_ALIGNMENT
ABORT, ALLBITS, ERROR, FRAMEBITS, HEIGHT, PROPERTIES, SOMEBITS, WIDTH
public Applet() throws HeadlessException
Constructs a new Applet.
Note: Many methods in java.applet.Applet
may be invoked by the applet only after the applet is fully constructed; applet should avoid calling methods in java.applet.Applet
in the constructor.
HeadlessException
- if GraphicsEnvironment.isHeadless() returns true.GraphicsEnvironment.isHeadless()
public final void setStub(AppletStub stub)
Sets this applet's stub. This is done automatically by the system.
If there is a security manager, its checkPermission
method is called with the AWTPermission("setAppletStub")
permission if a stub has already been set.
stub
- the new stub.SecurityException
- if the caller cannot set the stubpublic boolean isActive()
Determines if this applet is active. An applet is marked active just before its start
method is called. It becomes inactive just before its stop
method is called.
public URL getDocumentBase()
Gets the URL of the document in which this applet is embedded. For example, suppose an applet is contained within the document:
http://www.oracle.com/technetwork/java/index.htmlThe document base is:
http://www.oracle.com/technetwork/java/index.html
URL
of the document that contains this applet.getCodeBase()
public URL getCodeBase()
Gets the base URL. This is the URL of the directory which contains this applet.
URL
of the directory which contains this applet.getDocumentBase()
public String getParameter(String name)
Returns the value of the named parameter in the HTML tag. For example, if this applet is specified as
<applet code="Clock" width=50 height=50> <param name=Color value="blue"> </applet>
then a call to getParameter("Color")
returns the value "blue"
.
The name
argument is case insensitive.
name
- a parameter name.null
if not set.public AppletContext getAppletContext()
Determines this applet's context, which allows the applet to query and affect the environment in which it runs.
This environment of an applet represents the document that contains the applet.
public void resize(int width, int height)
Requests that this applet be resized.
resize
in class Component
width
- the new requested width for the applet.height
- the new requested height for the applet.public void resize(Dimension d)
Requests that this applet be resized.
public boolean isValidateRoot()
Indicates if this container is a validate root.
Applet
objects are the validate roots, and, therefore, they override this method to return true
.
isValidateRoot
in class Container
true
Container.isValidateRoot()
public void showStatus(String msg)
Requests that the argument string be displayed in the "status window". Many browsers and applet viewers provide such a window, where the application can inform users of its current state.
msg
- a string to display in the status window.public Image getImage(URL url)
Returns an Image
object that can then be painted on the screen. The url
that is passed as an argument must specify an absolute URL.
This method always returns immediately, whether or not the image exists. When this applet attempts to draw the image on the screen, the data will be loaded. The graphics primitives that draw the image will incrementally paint on the screen.
url
- an absolute URL giving the location of the image.Image
public Image getImage(URL url, String name)
Returns an Image
object that can then be painted on the screen. The url
argument must specify an absolute URL. The name
argument is a specifier that is relative to the url
argument.
This method always returns immediately, whether or not the image exists. When this applet attempts to draw the image on the screen, the data will be loaded. The graphics primitives that draw the image will incrementally paint on the screen.
url
- an absolute URL giving the base location of the image.name
- the location of the image, relative to the url
argument.Image
public static final AudioClip newAudioClip(URL url)
Get an audio clip from the given URL.
url
- points to the audio clippublic AudioClip getAudioClip(URL url)
Returns the AudioClip
object specified by the URL
argument.
This method always returns immediately, whether or not the audio clip exists. When this applet attempts to play the audio clip, the data will be loaded.
url
- an absolute URL giving the location of the audio clip.AudioClip
public AudioClip getAudioClip(URL url, String name)
Returns the AudioClip
object specified by the URL
and name
arguments.
This method always returns immediately, whether or not the audio clip exists. When this applet attempts to play the audio clip, the data will be loaded.
url
- an absolute URL giving the base location of the audio clip.name
- the location of the audio clip, relative to the url
argument.AudioClip
public String getAppletInfo()
Returns information about this applet. An applet should override this method to return a String
containing information about the author, version, and copyright of the applet.
The implementation of this method provided by the Applet
class returns null
.
public Locale getLocale()
Gets the locale of the applet. It allows the applet to maintain its own locale separated from the locale of the browser or appletviewer.
getLocale
in class Component
Component.setLocale(java.util.Locale)
public String[][] getParameterInfo()
Returns information about the parameters that are understood by this applet. An applet should override this method to return an array of Strings
describing these parameters.
Each element of the array should be a set of three Strings
containing the name, the type, and a description. For example:
String pinfo[][] = { {"fps", "1-10", "frames per second"}, {"repeat", "boolean", "repeat image loop"}, {"imgs", "url", "images directory"} };
The implementation of this method provided by the Applet
class returns null
.
public void play(URL url)
Plays the audio clip at the specified absolute URL. Nothing happens if the audio clip cannot be found.
url
- an absolute URL giving the location of the audio clip.public void play(URL url, String name)
Plays the audio clip given the URL and a specifier that is relative to it. Nothing happens if the audio clip cannot be found.
url
- an absolute URL giving the base location of the audio clip.name
- the location of the audio clip, relative to the url
argument.public void init()
Called by the browser or applet viewer to inform this applet that it has been loaded into the system. It is always called before the first time that the start
method is called.
A subclass of Applet
should override this method if it has initialization to perform. For example, an applet with threads would use the init
method to create the threads and the destroy
method to kill them.
The implementation of this method provided by the Applet
class does nothing.
public void start()
Called by the browser or applet viewer to inform this applet that it should start its execution. It is called after the init
method and each time the applet is revisited in a Web page.
A subclass of Applet
should override this method if it has any operation that it wants to perform each time the Web page containing it is visited. For example, an applet with animation might want to use the start
method to resume animation, and the stop
method to suspend the animation.
Note: some methods, such as getLocationOnScreen
, can only provide meaningful results if the applet is showing. Because isShowing
returns false
when the applet's start
is first called, methods requiring isShowing
to return true
should be called from a ComponentListener
.
The implementation of this method provided by the Applet
class does nothing.
destroy()
, init()
, stop()
, Component.isShowing()
, ComponentListener.componentShown(java.awt.event.ComponentEvent)
public void stop()
Called by the browser or applet viewer to inform this applet that it should stop its execution. It is called when the Web page that contains this applet has been replaced by another page, and also just before the applet is to be destroyed.
A subclass of Applet
should override this method if it has any operation that it wants to perform each time the Web page containing it is no longer visible. For example, an applet with animation might want to use the start
method to resume animation, and the stop
method to suspend the animation.
The implementation of this method provided by the Applet
class does nothing.
public void destroy()
Called by the browser or applet viewer to inform this applet that it is being reclaimed and that it should destroy any resources that it has allocated. The stop
method will always be called before destroy
.
A subclass of Applet
should override this method if it has any operation that it wants to perform before it is destroyed. For example, an applet with threads would use the init
method to create the threads and the destroy
method to kill them.
The implementation of this method provided by the Applet
class does nothing.
public AccessibleContext getAccessibleContext()
Gets the AccessibleContext associated with this Applet. For applets, the AccessibleContext takes the form of an AccessibleApplet. A new AccessibleApplet instance is created if necessary.
getAccessibleContext
in interface Accessible
getAccessibleContext
in class Panel
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