imageview.java

Mobile 应用程序使用 Java Micro Edition (Java ME) 平台

/*
 * @(#)ImageView.java	1.58 05/11/30
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */
package javax.swing.text.html;

import java.awt.*;
import java.awt.event.*;
import java.awt.image.ImageObserver;
import java.io.*;
import java.net.*;
import java.util.Dictionary;
import javax.swing.*;
import javax.swing.text.*;
import javax.swing.event.*;

/**
 * View of an Image, intended to support the HTML <IMG> tag.
 * Supports scaling via the HEIGHT and WIDTH attributes of the tag.
 * If the image is unable to be loaded any text specified via the
 * <code>ALT</code> attribute will be rendered.
 * <p>
 * While this class has been part of swing for a while now, it is public
 * as of 1.4.
 *
 * @author  Scott Violet
 * @version 1.58 11/30/05
 * @see IconView
 * @since 1.4
 */
public class ImageView extends View {
    /**
     * If true, when some of the bits are available a repaint is done.
     * <p>
     * This is set to false as swing does not offer a repaint that takes a
     * delay. If this were true, a bunch of immediate repaints would get
     * generated that end up significantly delaying the loading of the image
     * (or anything else going on for that matter).
     */
    private static boolean sIsInc = false;
    /**
     * Repaint delay when some of the bits are available.
     */
    private static int sIncRate = 100;
    /**
     * Property name for pending image icon
     */
    private static final String PENDING_IMAGE = "html.pendingImage";
    /**
     * Property name for missing image icon
     */
    private static final String MISSING_IMAGE = "html.missingImage";
    
    /**
     * Document property for image cache.
     */
    private static final String IMAGE_CACHE_PROPERTY = "imageCache";
    
    // Height/width to use before we know the real size, these should at least
    // the size of <code>sMissingImageIcon</code> and
    // <code>sPendingImageIcon</code>
    private static final int DEFAULT_WIDTH = 38;
    private static final int DEFAULT_HEIGHT= 38;

    /**
     * Default border to use if one is not specified.
     */
    private static final int DEFAULT_BORDER = 2;

    // Bitmask values
    private static final int LOADING_FLAG = 1;
    private static final int LINK_FLAG = 2;
    private static final int WIDTH_FLAG = 4;
    private static final int HEIGHT_FLAG = 8;
    private static final int RELOAD_FLAG = 16;
    private static final int RELOAD_IMAGE_FLAG = 32;
    private static final int SYNC_LOAD_FLAG = 64;

    private AttributeSet attr;
    private Image image;
    private int width;
    private int height;
    /** Bitmask containing some of the above bitmask values. Because the
     * image loading notification can happen on another thread access to
     * this is synchronized (at least for modifying it). */
    private int state;
    private Container container;
    private Rectangle fBounds;
    private Color borderColor;
    // Size of the border, the insets contains this valid. For example, if
    // the HSPACE attribute was 4 and BORDER 2, leftInset would be 6.
    private short borderSize;
    // Insets, obtained from the painter.
    private short leftInset;
    private short rightInset;
    private short topInset;
    private short bottomInset;
    /**
     * We don't directly implement ImageObserver, instead we use an instance
     * that calls back to us.
     */
    private ImageObserver imageObserver;
    /**
     * Used for alt text. Will be non-null if the image couldn't be found,
     * and there is valid alt text.
     */
    private View altView;
    /** Alignment along the vertical (Y) axis. */
    private float vAlign;



    /**
     * Creates a new view that represents an IMG element.
     *
     * @param elem the element to create a view for
     */
    public ImageView(Element elem) {
    	super(elem);
	fBounds = new Rectangle();
        imageObserver = new ImageHandler();
        state = RELOAD_FLAG | RELOAD_IMAGE_FLAG;
    }

    /**
     * Returns the text to display if the image can't be loaded. This is
     * obtained from the Elements attribute set with the attribute name
     * <code>HTML.Attribute.ALT</code>.
     */
    public String getAltText() {
        return (String)getElement().getAttributes().getAttribute
            (HTML.Attribute.ALT);
    }

    /**
     * Return a URL for the image source, 
     * or null if it could not be determined.
     */
    public URL getImageURL() {
 	String src = (String)getElement().getAttributes().
                             getAttribute(HTML.Attribute.SRC);
 	if (src == null) {
            return null;
        }

	URL reference = ((HTMLDocument)getDocument()).getBase();
        try {
 	    URL u = new URL(reference,src);
	    return u;
        } catch (MalformedURLException e) {
	    return null;
        }
    }
    
    /**
     * Returns the icon to use if the image couldn't be found.
     */
    public Icon getNoImageIcon() {
        return (Icon) UIManager.getLookAndFeelDefaults().get(MISSING_IMAGE);
    }

    /**
     * Returns the icon to use while in the process of loading the image.
     */
    public Icon getLoadingImageIcon() {
        return (Icon) UIManager.getLookAndFeelDefaults().get(PENDING_IMAGE);
    }

    /**
     * Returns the image to render.
     */
    public Image getImage() {
        sync();
        return image;
    }

    /**
     * Sets how the image is loaded. If <code>newValue</code> is true,
     * the image we be loaded when first asked for, otherwise it will
     * be loaded asynchronously. The default is to not load synchronously,
     * that is to load the image asynchronously.
     */
    public void setLoadsSynchronously(boolean newValue) {
        synchronized(this) {
            if (newValue) {
                state |= SYNC_LOAD_FLAG;
            }
            else {
                state = (state | SYNC_LOAD_FLAG) ^ SYNC_LOAD_FLAG;
            }
        }
    }

    /**
     * Returns true if the image should be loaded when first asked for.
     */
    public boolean getLoadsSynchronously() {
        return ((state & SYNC_LOAD_FLAG) != 0);
    }

    /**
     * Convenience method to get the StyleSheet.
     */
    protected StyleSheet getStyleSheet() {
	HTMLDocument doc = (HTMLDocument) getDocument();
	return doc.getStyleSheet();
    }

    /**
     * Fetches the attributes to use when rendering.  This is
     * implemented to multiplex the attributes specified in the
     * model with a StyleSheet.
     */
    public AttributeSet getAttributes() {
        sync();
	return attr;
    }

    /**
     * For images the tooltip text comes from text specified with the
     * <code>ALT</code> attribute. This is overriden to return
     * <code>getAltText</code>.
     *
     * @see JTextComponent#getToolTipText
     */
    public String getToolTipText(float x, float y, Shape allocation) {
        return getAltText();
    }

    /**
     * Update any cached values that come from attributes.
     */
    protected void setPropertiesFromAttributes() {
        StyleSheet sheet = getStyleSheet();
        this.attr = sheet.getViewAttributes(this);

        // Gutters
        borderSize = (short)getIntAttr(HTML.Attribute.BORDER, isLink() ?
                                       DEFAULT_BORDER : 0);

        leftInset = rightInset = (short)(getIntAttr(HTML.Attribute.HSPACE,
                                                    0) + borderSize);
        topInset = bottomInset = (short)(getIntAttr(HTML.Attribute.VSPACE,
                                                    0) + borderSize);

        borderColor = ((StyledDocument)getDocument()).getForeground
                      (getAttributes());

        AttributeSet attr = getElement().getAttributes();

        // Alignment.
        // PENDING: This needs to be changed to support the CSS versions
        // when conversion from ALIGN to VERTICAL_ALIGN is complete.
        Object alignment = attr.getAttribute(HTML.Attribute.ALIGN);

        vAlign = 1.0f;
        if (alignment != null) {
            alignment = alignment.toString();
            if ("top".equals(alignment)) {
                vAlign = 0f;
            }
            else if ("middle".equals(alignment)) {
                vAlign = .5f;
            }
        }

        AttributeSet anchorAttr = (AttributeSet)attr.getAttribute(HTML.Tag.A);
        if (anchorAttr != null && anchorAttr.isDefined
            (HTML.Attribute.HREF)) {
            synchronized(this) {
                state |= LINK_FLAG;
            }
        }
        else {
            synchronized(this) {
                state = (state | LINK_FLAG) ^ LINK_FLAG;
            }
        }
    }

    /**
     * Establishes the parent view for this view.
     * Seize this moment to cache the AWT Container I'm in.
     */
    public void setParent(View parent) {
        View oldParent = getParent();
	super.setParent(parent);
	container = (parent != null) ? getContainer() : null;
        if (oldParent != parent) {
            synchronized(this) {
                state |= RELOAD_FLAG;
            }
        }
    }

    /**
     * Invoked when the Elements attributes have changed. Recreates the image.
     */
    public void changedUpdate(DocumentEvent e, Shape a, ViewFactory f) {
    	super.changedUpdate(e,a,f);

        synchronized(this) {
            state |= RELOAD_FLAG | RELOAD_IMAGE_FLAG;
        }

        // Assume the worst.
        preferenceChanged(null, true, true);
    }

    /**
     * Paints the View.
     *
     * @param g the rendering surface to use
     * @param a the allocated region to render into
     * @see View#paint
     */
    public void paint(Graphics g, Shape a) {
        sync();

	Rectangle rect = (a instanceof Rectangle) ? (Rectangle)a :
                         a.getBounds();

        Image image = getImage();
        Rectangle clip = g.getClipBounds();