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Class java.applet.Applet - JDK 5 Documentation v1.1.8, Java 2 SDK 英文文档

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Class java.applet.Applet 

java.lang.Object
   |
   +----java.awt.Component
           |
           +----java.awt.Container
                   |
                   +----java.awt.Panel
                           |
                           +----java.applet.Applet
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.

Constructor Index

o Applet()

Method Index

o 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.
o getAppletContext()
Determines this applet's context, which allows the applet to query and affect the environment in which it runs.
o getAppletInfo()
Returns information about this applet.
o getAudioClip(URL)
Returns the AudioClip object specified by the URL argument.
o getAudioClip(URL, String)
Returns the AudioClip object specified by the URL and name arguments.
o getCodeBase()
Gets the base URL.
o getDocumentBase()
Gets the document URL.
o getImage(URL)
Returns an Image object that can then be painted on the screen.
o getImage(URL, String)
Returns an Image object that can then be painted on the screen.
o getLocale()
Gets the Locale for the applet, if it has been set.
o getParameter(String)
Returns the value of the named parameter in the HTML tag.
o getParameterInfo()
Returns information about the parameters than are understood by this applet.
o init()
Called by the browser or applet viewer to inform this applet that it has been loaded into the system.
o isActive()
Determines if this applet is active.
o play(URL)
Plays the audio clip at the specified absolute URL.
o play(URL, String)
Plays the audio clip given the URL and a specifier that is relative to it.
o resize(Dimension)
Requests that this applet be resized.
o resize(int, int)
Requests that this applet be resized.
o setStub(AppletStub)
Sets this applet's stub.
o showStatus(String)
Requests that the argument string be displayed in the "status window".
o start()
Called by the browser or applet viewer to inform this applet that it should start its execution.
o stop()
Called by the browser or applet viewer to inform this applet that it should stop its execution.

Constructors

o Applet 
 public Applet()

Methods

o setStub 
 public final void setStub(AppletStub stub)
Sets this applet's stub. This is done automatically by the system.

Parameters:
stub - the new stub.
o isActive 
 public boolean isActive()
Determines if this applet is active. An applet is marked active just before its start method is called. It becomes inactive immediately after its stop method is called.

Returns:
true if the applet is active; false otherwise.
See Also:
start, stop
o getDocumentBase 
 public URL getDocumentBase()
Gets the document URL. This is the URL of the document in which the applet is embedded.

Returns:
the URL of the document that contains this applet.
See Also:
getCodeBase
o getCodeBase 
 public URL getCodeBase()
Gets the base URL. This is the URL of the applet itself.

Returns:
the URL of this applet.
See Also:
getDocumentBase
o getParameter 
 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.

Parameters:
name - a parameter name.
Returns:
the value of the named parameter.
o getAppletContext 
 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.

Returns:
the applet's context.
o resize 
 public void resize(int width,
                    int height)
Requests that this applet be resized.

Parameters:
width - the new requested width for the applet.
height - the new requested height for the applet.
Overrides:
resize in class Component
o resize 
 public void resize(Dimension d)
Requests that this applet be resized.

Parameters:
d - an object giving the new width and height.
Overrides:
resize in class Component
o showStatus 
 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.

Parameters:
msg - a string to display in the status window.
o getImage 
 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.

Parameters:
url - an absolute URL giving the location of the image.
Returns:
the image at the specified URL.
See Also:
Image
o getImage 
 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.

Parameters:
url - an absolute URL giving the base location of the image.
name - the location of the image, relative to the url argument.
Returns:
the image at the specified URL.
See Also:
Image
o getAudioClip 
 public 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.

Parameters:
url - an absolute URL giving the location of the audio clip.
Returns:
the audio clip at the specified URL.
See Also:
AudioClip
o getAudioClip 
 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.

Parameters:
url - an absolute URL giving the base location of the audio clip.
name - the location of the audio clip, relative to the url argument.
Returns:
the audio clip at the specified URL.
See Also:
AudioClip
o getAppletInfo 
 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.

Returns:
a string containing information about the author, version, and copyright of the applet.
o getLocale 
 public Locale getLocale()
Gets the Locale for the applet, if it has been set. If no Locale has been set, then the default Locale is returned.

Returns:
[Needs to be documented!]
Overrides:
getLocale in class Component
o getParameterInfo 
 public String[][] getParameterInfo()
Returns information about the parameters than 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.

Returns:
an array describing the parameters this applet looks for.
o play 
 public void play(URL url)
Plays the audio clip at the specified absolute URL. Nothing happens if the audio clip cannot be found.

Parameters:
url - an absolute URL giving the location of the audio clip.
o play 
 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.

Parameters:
url - an absolute URL giving the base location of the audio clip.
name - the location of the audio clip, relative to the url argument.
o init 
 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.

See Also:
destroy, start, stop
o start 
 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.

The implementation of this method provided by the Applet class does nothing.

See Also:
destroy, init, stop
o stop 
 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.

See Also:
destroy, init
o destroy 
 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.

See Also:
init, start, stop 
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