toolkit.java

《移动Agent技术》一书的所有章节源代码。

/*
 * @(#)Toolkit.java	1.72 97/06/23
 * 
 * Copyright (c) 1995, 1996 Sun Microsystems, Inc. All Rights Reserved.
 * 
 * This software is the confidential and proprietary information of Sun
 * Microsystems, Inc. ("Confidential Information").  You shall not
 * disclose such Confidential Information and shall use it only in
 * accordance with the terms of the license agreement you entered into
 * with Sun.
 * 
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF THE
 * SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR
 * PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR ANY DAMAGES
 * SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR DISTRIBUTING
 * THIS SOFTWARE OR ITS DERIVATIVES.
 * 
 * CopyrightVersion 1.1_beta
 * 
 */

package java.awt;

import java.util.Properties;
import java.awt.peer.*;
import java.awt.image.ImageObserver;
import java.awt.image.ImageProducer;
import java.awt.image.ColorModel;
import java.awt.datatransfer.Clipboard;
import java.net.URL;
import java.io.BufferedInputStream;
import java.io.File;
import java.io.FileInputStream;

/**
 * This class is the abstract superclass of all actual
 * implementations of the Abstract Window Toolkit. Subclasses of 
 * <code>Toolkit</code> are used to bind the various components 
 * to particular native toolkit implementations.
 * <p>
 * Most applications should not call any of the methods in this
 * class directly. The methods defined by <code>Toolkit</code> are 
 * the "glue" that joins the platform-independent classes in the 
 * <code>java.awt</code> package with their counterparts in 
 * <code>java.awt.peer</code>. Some methods defined by 
 * <code>Toolkit</code> query the native operating system directly.
 *
 * @version 	1.72, 06/23/97
 * @author	Sami Shaio
 * @author	Arthur van Hoff
 * @since       JDK1.0
 */
public abstract class  Toolkit {

    /**
     * Creates this toolkit's implementation of <code>Button</code> using 
     * the specified peer interface.
     * @param     target the button to be implemented.
     * @return    this toolkit's implementation of <code>Button</code>.
     * @see       java.awt.Button
     * @see       java.awt.peer.ButtonPeer
     * @since     JDK1.0
     */
    protected abstract ButtonPeer 	createButton(Button target);

    /**
     * Creates this toolkit's implementation of <code>TextField</code> using 
     * the specified peer interface.
     * @param     target the text field to be implemented.
     * @return    this toolkit's implementation of <code>TextField</code>.
     * @see       java.awt.TextField
     * @see       java.awt.peer.TextFieldPeer
     * @since     JDK1.0
     */
    protected abstract TextFieldPeer 	createTextField(TextField target);

    /**
     * Creates this toolkit's implementation of <code>Label</code> using 
     * the specified peer interface.
     * @param     target the label to be implemented.
     * @return    this toolkit's implementation of <code>Label</code>.
     * @see       java.awt.Label
     * @see       java.awt.peer.LabelPeer
     * @since     JDK1.0
     */
    protected abstract LabelPeer 	createLabel(Label target);

    /**
     * Creates this toolkit's implementation of <code>List</code> using 
     * the specified peer interface.
     * @param     target the list to be implemented.
     * @return    this toolkit's implementation of <code>List</code>.
     * @see       java.awt.List
     * @see       java.awt.peer.ListPeer
     * @since     JDK1.0
     */
    protected abstract ListPeer 	createList(List target);

    /**
     * Creates this toolkit's implementation of <code>Checkbox</code> using 
     * the specified peer interface.
     * @param     target the check box to be implemented.
     * @return    this toolkit's implementation of <code>Checkbox</code>.
     * @see       java.awt.Checkbox
     * @see       java.awt.peer.CheckboxPeer
     * @since     JDK1.0
     */
    protected abstract CheckboxPeer 	createCheckbox(Checkbox target);

    /**
     * Creates this toolkit's implementation of <code>Scrollbar</code> using 
     * the specified peer interface.
     * @param     target the scroll bar to be implemented.
     * @return    this toolkit's implementation of <code>Scrollbar</code>.
     * @see       java.awt.Scrollbar
     * @see       java.awt.peer.ScrollbarPeer
     * @since     JDK1.0
     */
    protected abstract ScrollbarPeer 	createScrollbar(Scrollbar target);

    /**
     * Creates this toolkit's implementation of <code>ScrollPane</code> using 
     * the specified peer interface.
     * @param     target the scroll pane to be implemented.
     * @return    this toolkit's implementation of <code>ScrollPane</code>.
     * @see       java.awt.ScrollPane
     * @see       java.awt.peer.ScrollPanePeer
     * @since     JDK1.1
     */
    protected abstract ScrollPanePeer     createScrollPane(ScrollPane target);

    /**
     * Creates this toolkit's implementation of <code>TextArea</code> using 
     * the specified peer interface.
     * @param     target the text area to be implemented.
     * @return    this toolkit's implementation of <code>TextArea</code>.
     * @see       java.awt.TextArea
     * @see       java.awt.peer.TextAreaPeer
     * @since     JDK1.0
     */
    protected abstract TextAreaPeer  	createTextArea(TextArea target);

    /**
     * Creates this toolkit's implementation of <code>Choice</code> using 
     * the specified peer interface.
     * @param     target the choice to be implemented.
     * @return    this toolkit's implementation of <code>Choice</code>.
     * @see       java.awt.Choice
     * @see       java.awt.peer.ChoicePeer
     * @since     JDK1.0
     */
    protected abstract ChoicePeer	createChoice(Choice target);

    /**
     * Creates this toolkit's implementation of <code>Frame</code> using 
     * the specified peer interface.
     * @param     target the frame to be implemented.
     * @return    this toolkit's implementation of <code>Frame</code>.
     * @see       java.awt.Frame
     * @see       java.awt.peer.FramePeer
     * @since     JDK1.0
     */
    protected abstract FramePeer  	createFrame(Frame target);

    /**
     * Creates this toolkit's implementation of <code>Canvas</code> using 
     * the specified peer interface.
     * @param     target the canvas to be implemented.
     * @return    this toolkit's implementation of <code>Canvas</code>.
     * @see       java.awt.Canvas
     * @see       java.awt.peer.CanvasPeer
     * @since     JDK1.0
     */
    protected abstract CanvasPeer 	createCanvas(Canvas target);

    /**
     * Creates this toolkit's implementation of <code>Panel</code> using 
     * the specified peer interface.
     * @param     target the panel to be implemented.
     * @return    this toolkit's implementation of <code>Panel</code>.
     * @see       java.awt.Panel
     * @see       java.awt.peer.PanelPeer
     * @since     JDK1.0
     */
    protected abstract PanelPeer  	createPanel(Panel target);

    /**
     * Creates this toolkit's implementation of <code>Window</code> using 
     * the specified peer interface.
     * @param     target the window to be implemented.
     * @return    this toolkit's implementation of <code>Window</code>.
     * @see       java.awt.Window
     * @see       java.awt.peer.WindowPeer
     * @since     JDK1.0
     */
    protected abstract WindowPeer  	createWindow(Window target);

    /**
     * Creates this toolkit's implementation of <code>Dialog</code> using 
     * the specified peer interface.
     * @param     target the dialog to be implemented.
     * @return    this toolkit's implementation of <code>Dialog</code>.
     * @see       java.awt.Dialog
     * @see       java.awt.peer.DialogPeer
     * @since     JDK1.0
     */
    protected abstract DialogPeer  	createDialog(Dialog target);

    /**
     * Creates this toolkit's implementation of <code>MenuBar</code> using 
     * the specified peer interface.
     * @param     target the menu bar to be implemented.
     * @return    this toolkit's implementation of <code>MenuBar</code>.
     * @see       java.awt.MenuBar
     * @see       java.awt.peer.MenuBarPeer
     * @since     JDK1.0
     */
    protected abstract MenuBarPeer  	createMenuBar(MenuBar target);

    /**
     * Creates this toolkit's implementation of <code>Menu</code> using 
     * the specified peer interface.
     * @param     target the menu to be implemented.
     * @return    this toolkit's implementation of <code>Menu</code>.
     * @see       java.awt.Menu
     * @see       java.awt.peer.MenuPeer
     * @since     JDK1.0
     */
    protected abstract MenuPeer  	createMenu(Menu target);

    /**
     * Creates this toolkit's implementation of <code>PopupMenu</code> using 
     * the specified peer interface.
     * @param     target the popup menu to be implemented.
     * @return    this toolkit's implementation of <code>PopupMenu</code>.
     * @see       java.awt.PopupMenu
     * @see       java.awt.peer.PopupMenuPeer
     * @since     JDK1.1
     */
    protected abstract PopupMenuPeer	createPopupMenu(PopupMenu target);

    /**
     * Creates this toolkit's implementation of <code>MenuItem</code> using 
     * the specified peer interface.
     * @param     target the menu item to be implemented.
     * @return    this toolkit's implementation of <code>MenuItem</code>.
     * @see       java.awt.MenuItem
     * @see       java.awt.peer.MenuItemPeer
     * @since     JDK1.0
     */
    protected abstract MenuItemPeer  	createMenuItem(MenuItem target);

    /**
     * Creates this toolkit's implementation of <code>FileDialog</code> using 
     * the specified peer interface.
     * @param     target the file dialog to be implemented.
     * @return    this toolkit's implementation of <code>FileDialog</code>.
     * @see       java.awt.FileDialog
     * @see       java.awt.peer.FileDialogPeer
     * @since     JDK1.0
     */
    protected abstract FileDialogPeer	createFileDialog(FileDialog target);

    /**
     * Creates this toolkit's implementation of <code>CheckboxMenuItem</code> using 
     * the specified peer interface.
     * @param     target the checkbox menu item to be implemented.
     * @return    this toolkit's implementation of <code>CheckboxMenuItem</code>.
     * @see       java.awt.CheckboxMenuItem
     * @see       java.awt.peer.CheckboxMenuItemPeer
     * @since     JDK1.0
     */
    protected abstract CheckboxMenuItemPeer	createCheckboxMenuItem(CheckboxMenuItem target);

    /**
     * Creates a peer for a component or container.  This peer is windowless
     * and allows the Component and Container classes to be extended directly
     * to create windowless components that are defined entirely in java.
     *
     * @param target The Component to be created.
     */
    protected java.awt.peer.LightweightPeer createComponent(Component target) {
	return new java.awt.LightweightPeer(target);
    }

    /**
     * Creates this toolkit's implementation of <code>Font</code> using 
     * the specified peer interface.
     * @param     target the font to be implemented.
     * @return    this toolkit's implementation of <code>Font</code>.
     * @see       java.awt.Font
     * @see       java.awt.peer.FontPeer
     * @since     JDK1.0
     */
    protected abstract FontPeer getFontPeer(String name, int style);

    /**
     * Fills in the integer array that is supplied as an argument 
     * with the current system color values.
     * <p>
     * This method is called by the method <code>updateSystemColors</code>
     * in the <code>SystemColor</code> class.
     * @param     an integer array.
     * @see       java.awt.SystemColor#updateSystemColors
     * @since     JDK1.1
     */
    protected void loadSystemColors(int[] systemColors) {
    }

    /**
     * Gets the size of the screen.
     * @return    the size of this toolkit's screen, in pixels.
     * @since     JDK1.0
     */
    public abstract Dimension getScreenSize();

    /**
     * Returns the screen resolution in dots-per-inch.
     * @return    this toolkit's screen resolution, in dots-per-inch.
     * @since     JDK1.0
     */
    public abstract int getScreenResolution();

    /**
     * Determines the color model of this toolkit's screen. 
     * <p>
     * <code>ColorModel</code> is an abstract class that 
     * encapsulates the ability to translate between the 
     * pixel values of an image and its red, green, blue, 
     * and alpha components. 
     * <p>
     * This toolkit method is called by the 
     * <code>getColorModel</code> method 
     * of the <code>Component</code> class. 
     * @return    the color model of this toolkit's screen.
     * @see       java.awt.image.ColorModel
     * @see       java.awt.Component#getColorModel
     * @since     JDK1.0
     */
    public abstract ColorModel getColorModel();

    /**
     * Returns the names of the available fonts in this toolkit.<p>
     * For 1.1, the following font names are deprecated (the replacement
     * name follows):
     * <ul>
     * <li>TimesRoman (use Serif)
     * <li>Helvetica (use SansSerif)
     * <li>Courier (use Monospaced)
     * </ul><p>
     * The ZapfDingbats font is also deprecated in 1.1, but only as a
     * separate fontname.  Unicode defines the ZapfDingbat characters
     * starting at \u2700, and as of 1.1 Java supports those characters.
     * @return    the names of the available fonts in this toolkit.
     * @since     JDK1.0
     */
    public abstract String[] getFontList();

    /**
     * Gets the screen metrics of the font.
     * @param     font   a font.
     * @return    the screen metrics of the specified font in this toolkit.
     * @since     JDK1.0
     */
    public abstract FontMetrics getFontMetrics(Font font);

    /**
     * Synchronizes this toolkit's graphics state. Some window systems 
     * may do buffering of graphics events. 
     * <p>
     * This method ensures that the display is up-to-date. It is useful
     * for animation.
     * @since     JDK1.0
     */
    public abstract void sync();

    /**
     * The default toolkit.
     */
    private static Toolkit toolkit;

    /**
     * Gets the default toolkit. 
     * <p>
     * If there is a system property named <code>"awt.toolkit"</code>, 
     * that property is treated as the name of a class that is a subclass 
     * of <code>Toolkit</code>. 
     * <p>
     * If the system property does not exist, then the default toolkit 
     * used is the class named <code>"sun.awt.motif.MToolkit"</code>, 
     * which is a motif implementation of the Abstract Window Toolkit. 
     * @return    the default toolkit.
     * @exception  AWTError  if a toolkit could not be found, or 
     *                 if one could not be accessed or instantiated.
     * @since     JDK1.0
     */
    public static synchronized Toolkit getDefaultToolkit() {
	if (toolkit == null) {
	    String nm = System.getProperty("awt.toolkit", "sun.awt.motif.MToolkit");
	    try {
		toolkit = (Toolkit)Class.forName(nm).newInstance();
	    } catch (ClassNotFoundException e) {
		throw new AWTError("Toolkit not found: " + nm);
	    } catch (InstantiationException e) {
		throw new AWTError("Could not instantiate Toolkit: " + nm);