appletcontext.java

applet 小程序 提供给大家学习参考

/*
 * @(#)AppletContext.java	1.31 04/05/05
 *
 * Copyright 2004 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.applet;

import java.awt.Image;
import java.awt.Graphics;
import java.awt.image.ColorModel;
import java.net.URL;
import java.util.Enumeration;
import java.io.InputStream;
import java.io.IOException;
import java.util.Iterator;

/**
 * This interface corresponds to an applet's environment: the
 * document containing the applet and the other applets in the same
 * document.
 * <p>
 * The methods in this interface can be used by an applet to obtain
 * information about its environment.
 *
 * @author 	Arthur van Hoff
 * @version     1.31, 05/05/04
 * @since       JDK1.0
 */
public interface AppletContext {
    /**
     * Creates an audio clip.
     *
     * @param   url   an absolute URL giving the location of the audio clip.
     * @return  the audio clip at the specified URL.
     */
    AudioClip getAudioClip(URL url);

    /**
     * Returns an <code>Image</code> object that can then be painted on
     * the screen. The <code>url</code> argument<code> </code>that is
     * passed as an argument must specify an absolute URL.
     * <p>
     * This method always returns immediately, whether or not the image
     * exists. When the 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 location of the image.
     * @return  the image at the specified URL.
     * @see     java.awt.Image
     */
    Image getImage(URL url);

    /**
     * Finds and returns the applet in the document represented by this
     * applet context with the given name. The name can be set in the
     * HTML tag by setting the <code>name</code> attribute.
     *
     * @param   name   an applet name.
     * @return  the applet with the given name, or <code>null</code> if
     *          not found.
     */
    Applet getApplet(String name);

    /**
     * Finds all the applets in the document represented by this applet
     * context.
     *
     * @return  an enumeration of all applets in the document represented by
     *          this applet context.
     */
    Enumeration<Applet> getApplets();

    /**
     * Replaces the Web page currently being viewed with the given URL.
     * This method may be ignored by applet contexts that are not
     * browsers.
     *
     * @param   url   an absolute URL giving the location of the document.
     */
    void showDocument(URL url);

    /**
     * Requests that the browser or applet viewer show the Web page
     * indicated by the <code>url</code> argument. The
     * <code>target</code> argument indicates in which HTML frame the
     * document is to be displayed.
     * The target argument is interpreted as follows:
     * <p>
     * <center><table border="3" summary="Target arguments and their descriptions">
     * <tr><th>Target Argument</th><th>Description</th></tr>
     * <tr><td><code>"_self"</code>  <td>Show in the window and frame that
     *                                   contain the applet.</tr>
     * <tr><td><code>"_parent"</code><td>Show in the applet's parent frame. If
     *                                   the applet's frame has no parent frame,
     *                                   acts the same as "_self".</tr>
     * <tr><td><code>"_top"</code>   <td>Show in the top-level frame of the applet's
     *                                   window. If the applet's frame is the
     *                                   top-level frame, acts the same as "_self".</tr>
     * <tr><td><code>"_blank"</code> <td>Show in a new, unnamed
     *                                   top-level window.</tr>
     * <tr><td><i>name</i><td>Show in the frame or window named <i>name</i>. If
     *                        a target named <i>name</i> does not already exist, a
     *                        new top-level window with the specified name is created,
     *                        and the document is shown there.</tr>
     * </table> </center>
     * <p>
     * An applet viewer or browser is free to ignore <code>showDocument</code>.
     *
     * @param   url   an absolute URL giving the location of the document.
     * @param   target   a <code>String</code> indicating where to display
     *                   the page.
     */
    public void showDocument(URL url, String target);

    /**
     * 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   status   a string to display in the status window.
     */
    void showStatus(String status);

    /**
     * Associates the specified stream with the specified key in this
     * applet context. If the applet context previously contained a mapping 
     * for this key, the old value is replaced. 
     * <p>
     * For security reasons, mapping of streams and keys exists for each 
     * codebase. In other words, applet from one codebase cannot access 
     * the streams created by an applet from a different codebase
     * <p>
     * @param key key with which the specified value is to be associated.
     * @param stream stream to be associated with the specified key. If this
     *               parameter is <code>null<code>, the specified key is removed 
     *               in this applet context.
     * @throws <code>IOException</code> if the stream size exceeds a certain
     *         size limit. Size limit is decided by the implementor of this
     *         interface.
     * @since JDK1.4
     */
    public void setStream(String key, InputStream stream)throws IOException;

    /**
     * Returns the stream to which specified key is associated within this 
     * applet context. Returns <tt>null</tt> if the applet context contains 
     * no stream for this key.  
     * <p>
     * For security reasons, mapping of streams and keys exists for each 
     * codebase. In other words, applet from one codebase cannot access 
     * the streams created by an applet from a different codebase
     * <p>
     * @return the stream to which this applet context maps the key
     * @param key key whose associated stream is to be returned.
     * @since JDK1.4
     */
    public InputStream getStream(String key);

    /**
     * Finds all the keys of the streams in this applet context.
     * <p>
     * For security reasons, mapping of streams and keys exists for each 
     * codebase. In other words, applet from one codebase cannot access 
     * the streams created by an applet from a different codebase
     * <p>
     * @return  an Iterator of all the names of the streams in this applet 
     *          context.
     * @since JDK1.4
     */
    public Iterator<String> getStreamKeys();
}