JDK14/Java14源码在线阅读
/*
* Copyright (c) 1995, 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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*/
package java.applet;
import java.awt.AWTPermission;
import java.awt.Dimension;
import java.awt.GraphicsEnvironment;
import java.awt.HeadlessException;
import java.awt.Image;
import java.awt.Panel;
import java.awt.event.ComponentEvent;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.net.MalformedURLException;
import java.net.URL;
import java.util.Locale;
import javax.accessibility.AccessibleContext;
import javax.accessibility.AccessibleRole;
import javax.accessibility.AccessibleState;
import javax.accessibility.AccessibleStateSet;
import com.sun.media.sound.JavaSoundAudioClip;
/**
* An applet is a small program that is intended not to be run on its own, but
* rather to be embedded inside another application.
* <p>
* The {@code 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
* {@code Applet} class provides a standard interface between applets and their
* environment.
*
* @author Arthur van Hoff
* @author Chris Warth
* @since 1.0
* @deprecated The Applet API is deprecated, no replacement.
*/
@Deprecated(since = "9")
public class Applet extends Panel {
/**
* Constructs a new Applet.
* <p>
* Note: Many methods in {@code java.applet.Applet} may be invoked by the
* applet only after the applet is fully constructed; applet should avoid
* calling methods in {@code java.applet.Applet} in the constructor.
*
* @throws HeadlessException if {@code GraphicsEnvironment.isHeadless()}
* returns {@code true}
* @see java.awt.GraphicsEnvironment#isHeadless
* @since 1.4
*/
public Applet() throws HeadlessException {
if (GraphicsEnvironment.isHeadless()) {
throw new HeadlessException();
}
}
/**
* Applets can be serialized but the following conventions MUST be followed:
* <p>
* Before Serialization: An applet must be in STOPPED state.
* <p>
* After Deserialization: The applet will be restored in STOPPED state (and
* most clients will likely move it into RUNNING state). The stub field will
* be restored by the reader.
*/
private transient AppletStub stub;
/**
* Use serialVersionUID from JDK 1.0 for interoperability.
*/
private static final long serialVersionUID = -5836846270535785031L;
/**
* Read an applet from an object input stream.
*
* @param s an object input stream
* @throws HeadlessException if {@code GraphicsEnvironment.isHeadless()}
* returns {@code true}
* @serial
* @see java.awt.GraphicsEnvironment#isHeadless
* @since 1.4
*/
private void readObject(ObjectInputStream s)
throws ClassNotFoundException, IOException, HeadlessException {
if (GraphicsEnvironment.isHeadless()) {
throw new HeadlessException();
}
s.defaultReadObject();
}
/**
* Sets this applet's stub. This is done automatically by the system.
* <p>
* If there is a security manager, its {@code checkPermission} method is
* called with the {@code AWTPermission("setAppletStub")} permission if a
* stub has already been set.
*
* @param stub the new stub
* @throws SecurityException if the caller cannot set the stub
*/
public final void setStub(AppletStub stub) {
if (this.stub != null) {
SecurityManager s = System.getSecurityManager();
if (s != null) {
s.checkPermission(new AWTPermission("setAppletStub"));
}
}
this.stub = stub;
}
/**
* Determines if this applet is active. An applet is marked active just
* before its {@code start} method is called. It becomes inactive just
* before its {@code stop} method is called.
*
* @return {@code true} if the applet is active; {@code false} otherwise
* @see java.applet.Applet#start()
* @see java.applet.Applet#stop()
*/
public boolean isActive() {
if (stub != null) {
return stub.isActive();
} else { // If stub field not filled in, applet never active
return false;
}
}
/**
* Gets the {@code URL} of the document in which this applet is embedded.
* For example, suppose an applet is contained within the document:
* <blockquote><pre>
* http://www.oracle.com/technetwork/java/index.html
* </pre></blockquote>
* The document base is:
* <blockquote><pre>
* http://www.oracle.com/technetwork/java/index.html
* </pre></blockquote>
*
* @return the {@link java.net.URL} of the document that contains this
* applet
* @see java.applet.Applet#getCodeBase()
*/
public URL getDocumentBase() {
return stub.getDocumentBase();
}
/**
* Gets the base {@code URL}. This is the {@code URL} of the directory which
* contains this applet.
*
* @return the base {@link java.net.URL} of the directory which contains
* this applet
* @see java.applet.Applet#getDocumentBase()
*/
public URL getCodeBase() {
return stub.getCodeBase();
}
/**
* Returns the value of the named parameter in the HTML tag. For example, if
* this applet is specified as
* <blockquote><pre>
* <applet code="Clock" width=50 height=50>
* <param name=Color value="blue">
* </applet>
* </pre></blockquote>
* <p>
* then a call to {@code getParameter("Color")} returns the value
* {@code "blue"}.
* <p>
* The {@code name} argument is case insensitive.
*
* @param name a parameter name
* @return the value of the named parameter, or {@code null} if not set
*/
public String getParameter(String name) {
return stub.getParameter(name);
}
/**
* Determines this applet's context, which allows the applet to query and
* affect the environment in which it runs.
* <p>
* This environment of an applet represents the document that contains the
* applet.
*
* @return the applet's context
*/
public AppletContext getAppletContext() {
return stub.getAppletContext();
}
/**
* Requests that this applet be resized.
*
* @param width the new requested width for the applet
* @param height the new requested height for the applet
*/
@SuppressWarnings("deprecation")
public void resize(int width, int height) {
Dimension d = size();
if ((d.width != width) || (d.height != height)) {
super.resize(width, height);
if (stub != null) {
stub.appletResize(width, height);
}
}
}
/**
* Requests that this applet be resized.
*
* @param d an object giving the new width and height
*/
@SuppressWarnings("deprecation")
public void resize(Dimension d) {
resize(d.width, d.height);
}
/**
* Indicates if this container is a validate root.
* <p>
* {@code Applet} objects are the validate roots, and, therefore, they
* override this method to return {@code true}.
*
* @return {@code true}
* @see java.awt.Container#isValidateRoot
* @since 1.7
*/
@Override
public boolean isValidateRoot() {
return true;
}
/**
* 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.
*
* @param msg a string to display in the status window
*/
public void showStatus(String msg) {
getAppletContext().showStatus(msg);
}
/**
* Returns an {@code Image} object that can then be painted on the screen.
* The {@code url} that is passed as an argument must specify an absolute
* {@code URL}.
* <p>
* 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.
*
* @param url an absolute {@code URL} giving the location of the image
* @return the image at the specified {@code URL}
* @see java.awt.Image
*/
public Image getImage(URL url) {
return getAppletContext().getImage(url);
}
/**
* Returns an {@code Image} object that can then be painted on the screen.
* The {@code url} argument must specify an absolute {@code URL}. The
* {@code name} argument is a specifier that is relative to the {@code url}
* argument.
* <p>
* 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.
*
* @param url an absolute URL giving the base location of the image
* @param name the location of the image, relative to the {@code url}
* argument
* @return the image at the specified {@code URL}
* @see java.awt.Image
*/
public Image getImage(URL url, String name) {
try {
return getImage(new URL(url, name));
} catch (MalformedURLException e) {
return null;
}
}
/**
* Get an audio clip from the given {@code URL}.
*
* @param url points to the audio clip
* @return the audio clip at the specified {@code URL}
* @since 1.2
*/
public static final AudioClip newAudioClip(URL url) {
return JavaSoundAudioClip.create(url);
}
/**
* Returns the {@code AudioClip} object specified by the {@code URL}
* argument.
* <p>
* 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.
*
* @param url an absolute {@code URL} giving the location of the audio clip
* @return the audio clip at the specified {@code URL}
* @see java.applet.AudioClip
*/
public AudioClip getAudioClip(URL url) {
return getAppletContext().getAudioClip(url);
}
/**
* Returns the {@code AudioClip} object specified by the {@code URL} and
* {@code name} arguments.
* <p>
* 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.
*
* @param url an absolute {@code URL} giving the base location of the audio
* clip
* @param name the location of the audio clip, relative to the {@code url}
* argument
* @return the audio clip at the specified {@code URL}
* @see java.applet.AudioClip
*/
public AudioClip getAudioClip(URL url, String name) {
try {
return getAudioClip(new URL(url, name));
} catch (MalformedURLException e) {
return null;
}
}
/**
* Returns information about this applet. An applet should override this
* method to return a {@code String} containing information about the
* author, version, and copyright of the applet.
* <p>
* The implementation of this method provided by the {@code Applet} class
* returns {@code null}.
*
* @return a string containing information about the author, version, and
* copyright of the applet
*/
public String getAppletInfo() {
return null;
}
/**
* Gets the locale of the applet. It allows the applet to maintain its own
* locale separated from the locale of the browser or appletviewer.
*
* @return the locale of the applet; if no locale has been set, the default
* locale is returned
* @since 1.1
*/
public Locale getLocale() {
Locale locale = super.getLocale();
if (locale == null) {
return Locale.getDefault();
}
return locale;
}
/**
* 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.
* <p>
* Each element of the array should be a set of three strings containing the
* name, the type, and a description. For example:
* <blockquote><pre>
* String pinfo[][] = {
* {"fps", "1-10", "frames per second"},
* {"repeat", "boolean", "repeat image loop"},
* {"imgs", "url", "images directory"}
* };
* </pre></blockquote>
* <p>
* The implementation of this method provided by the {@code Applet} class
* returns {@code null}.
*
* @return an array describing the parameters this applet looks for
*/
public String[][] getParameterInfo() {
return null;
}
/**
* Plays the audio clip at the specified absolute {@code URL}. Nothing
* happens if the audio clip cannot be found.
*
* @param url an absolute {@code URL} giving the location of the audio clip
*/
public void play(URL url) {
AudioClip clip = getAudioClip(url);
if (clip != null) {
clip.play();
}
}
/**
* Plays the audio clip given the {@code URL} and a specifier that is
* relative to it. Nothing happens if the audio clip cannot be found.
*
* @param url an absolute {@code URL} giving the base location of the audio
* clip
* @param name the location of the audio clip, relative to the {@code url}
* argument
*/
public void play(URL url, String name) {
AudioClip clip = getAudioClip(url, name);
if (clip != null) {
clip.play();
}
}
/**
* 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 {@code start} method is called.
* <p>
* A subclass of {@code Applet} should override this method if it has
* initialization to perform. For example, an applet with threads would use
* the {@code init} method to create the threads and the {@code destroy}
* method to kill them.
* <p>
* The implementation of this method provided by the {@code Applet} class
* does nothing.
*
* @see java.applet.Applet#destroy()
* @see java.applet.Applet#start()
* @see java.applet.Applet#stop()
*/
public void init() {
}
/**
* Called by the browser or applet viewer to inform this applet that it
* should start its execution. It is called after the {@code init} method
* and each time the applet is revisited in a Web page.
* <p>
* A subclass of {@code 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
* {@code start} method to resume animation, and the {@code stop} method to
* suspend the animation.
* <p>
* Note: some methods, such as {@code getLocationOnScreen}, can only provide
* meaningful results if the applet is showing. Because {@code isShowing}
* returns {@code false} when the applet's {@code start} is first called,
* methods requiring {@code isShowing} to return {@code true} should be
* called from a {@code ComponentListener}.
* <p>
* The implementation of this method provided by the {@code Applet} class
* does nothing.
*
* @see java.applet.Applet#destroy()
* @see java.applet.Applet#init()
* @see java.applet.Applet#stop()
* @see java.awt.Component#isShowing()
* @see java.awt.event.ComponentListener#componentShown(ComponentEvent)
*/
public void start() {
}
/**
* 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.
* <p>
* A subclass of {@code 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 {@code start} method to resume animation, and the {@code stop}
* method to suspend the animation.
* <p>
* The implementation of this method provided by the {@code Applet} class
* does nothing.
*
* @see java.applet.Applet#destroy()
* @see java.applet.Applet#init()
*/
public void stop() {
}
/**
* 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 {@code stop} method will always be called before
* {@code destroy}.
* <p>
* A subclass of {@code 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 {@code init} method to create the
* threads and the {@code destroy} method to kill them.
* <p>
* The implementation of this method provided by the {@code Applet} class
* does nothing.
*
* @see java.applet.Applet#init()
* @see java.applet.Applet#start()
* @see java.applet.Applet#stop()
*/
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