imageview.java

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

                // Clear out state in case someone threw an exception.
                state = (state | LOADING_FLAG) ^ LOADING_FLAG;
            }
        }
    }

    /**
     * Loads the image from the URL <code>getImageURL</code>. This should
     * only be invoked from <code>refreshImage</code>.
     */
    private void loadImage() {
        URL src = getImageURL();
        Image newImage = null;
        if (src != null) {
            Dictionary cache = (Dictionary)getDocument().
                                    getProperty(IMAGE_CACHE_PROPERTY);
            if (cache != null) {
                newImage = (Image)cache.get(src);
            }
            else {
                newImage = Toolkit.getDefaultToolkit().createImage(src);
                if (newImage != null && getLoadsSynchronously()) {
                    // Force the image to be loaded by using an ImageIcon.
                    ImageIcon ii = new ImageIcon();
                    ii.setImage(newImage);
                }
            }
        }
        image = newImage;
    }

    /**
     * Recreates and reloads the image.  This should
     * only be invoked from <code>refreshImage</code>.
     */
    private void updateImageSize() {
	int newWidth = 0;
	int newHeight = 0;
        int newState = 0;
        Image newImage = getImage();

        if (newImage != null) {
            Element elem = getElement();
	    AttributeSet attr = elem.getAttributes();

            // Get the width/height and set the state ivar before calling
            // anything that might cause the image to be loaded, and thus the
            // ImageHandler to be called.
	    newWidth = getIntAttr(HTML.Attribute.WIDTH, -1);
            if (newWidth > 0) {
                newState |= WIDTH_FLAG;
            }
	    newHeight = getIntAttr(HTML.Attribute.HEIGHT, -1);
            if (newHeight > 0) {
                newState |= HEIGHT_FLAG;
            }

            if (newWidth <= 0) {
		newWidth = newImage.getWidth(imageObserver);
                if (newWidth <= 0) {
                    newWidth = DEFAULT_WIDTH;
                }
            }

            if (newHeight <= 0) {
		newHeight = newImage.getHeight(imageObserver);
                if (newHeight <= 0) {
                    newHeight = DEFAULT_HEIGHT;
                }
            }

	    // Make sure the image starts loading:
            if ((newState & (WIDTH_FLAG | HEIGHT_FLAG)) != 0) {
                Toolkit.getDefaultToolkit().prepareImage(newImage, newWidth,
                                                         newHeight,
                                                         imageObserver);
            }
            else {
                Toolkit.getDefaultToolkit().prepareImage(newImage, -1, -1,
                                                         imageObserver);
            }

            boolean createText = false;
	    synchronized(this) {
                // If imageloading failed, other thread may have called
                // ImageLoader which will null out image, hence we check
                // for it.
                if (image != null) {
                    if ((newState & WIDTH_FLAG) == WIDTH_FLAG || width == 0) {
                        width = newWidth;
                    }
                    if ((newState & HEIGHT_FLAG) == HEIGHT_FLAG ||
                        height == 0) {
                        height = newHeight;
                    }
                }
                else {
                    createText = true;
                    if ((newState & WIDTH_FLAG) == WIDTH_FLAG) {
                        width = newWidth;
                    }
                    if ((newState & HEIGHT_FLAG) == HEIGHT_FLAG) {
                        height = newHeight;
                    }
                }
                state = state | newState;
                state = (state | LOADING_FLAG) ^ LOADING_FLAG;
            }
            if (createText) {
                // Only reset if this thread determined image is null
                updateAltTextView();
	    }
	}
        else {
            width = height = DEFAULT_HEIGHT;
            updateAltTextView();
        }
    }

    /**
     * Updates the view representing the alt text.
     */
    private void updateAltTextView() {
        String text = getAltText();

        if (text != null) {
            ImageLabelView newView;

            newView = new ImageLabelView(getElement(), text);
            synchronized(this) {
                altView = newView;
            }
        }
    }

    /**
     * Returns the view to use for alternate text. This may be null.
     */
    private View getAltView() {
        View view;

        synchronized(this) {
            view = altView;
        }
        if (view != null && view.getParent() == null) {
            view.setParent(getParent());
        }
        return view;
    }

    /**
     * Invokes <code>preferenceChanged</code> on the event displatching
     * thread.
     */
    private void safePreferenceChanged() {
        if (SwingUtilities.isEventDispatchThread()) {
	    Document doc = getDocument();
	    if (doc instanceof AbstractDocument) {
		((AbstractDocument)doc).readLock();
	    }
            preferenceChanged(null, true, true);
	    if (doc instanceof AbstractDocument) {
		((AbstractDocument)doc).readUnlock();
	    }
        }
        else {
            SwingUtilities.invokeLater(new Runnable() {
                    public void run() {
                        safePreferenceChanged();
                    }
                });
        }
    }

    /**
     * ImageHandler implements the ImageObserver to correctly update the
     * display as new parts of the image become available.
     */
    private class ImageHandler implements ImageObserver {
        // This can come on any thread. If we are in the process of reloading
        // the image and determining our state (loading == true) we don't fire
        // preference changed, or repaint, we just reset the fWidth/fHeight as
        // necessary and return. This is ok as we know when loading finishes
        // it will pick up the new height/width, if necessary.
        public boolean imageUpdate(Image img, int flags, int x, int y,
                                   int newWidth, int newHeight ) {
            if (image == null || image != img || getParent() == null) {
                return false;
            }
    	    
            // Bail out if there was an error:
            if ((flags & (ABORT|ERROR)) != 0) {
                repaint(0);
                synchronized(ImageView.this) {
                    if (image == img) {
                        // Be sure image hasn't changed since we don't
                        // initialy synchronize
                        image = null;
                        if ((state & WIDTH_FLAG) != WIDTH_FLAG) {
                            width = DEFAULT_WIDTH;
                        }
                        if ((state & HEIGHT_FLAG) != HEIGHT_FLAG) {
                            height = DEFAULT_HEIGHT;
                        }
                    }
                    if ((state & LOADING_FLAG) == LOADING_FLAG) {
                        // No need to resize or repaint, still in the process
                        // of loading.
                        return false;
                    }
                }
                updateAltTextView();
                safePreferenceChanged();
                return false;
            }

            // Resize image if necessary:
            short changed = 0;
            if ((flags & ImageObserver.HEIGHT) != 0 && !getElement().
                  getAttributes().isDefined(HTML.Attribute.HEIGHT)) {
                changed |= 1;
            }
            if ((flags & ImageObserver.WIDTH) != 0 && !getElement().
                  getAttributes().isDefined(HTML.Attribute.WIDTH)) {
		changed |= 2;
            }

            synchronized(ImageView.this) {
                if (image != img) {
                    return false;
                }
                if ((changed & 1) == 1 && (state & WIDTH_FLAG) == 0) {
                    width = newWidth;
                }
                if ((changed & 2) == 2 && (state & HEIGHT_FLAG) == 0) {
                    height = newHeight;
                }
                if ((state & LOADING_FLAG) == LOADING_FLAG) {
                    // No need to resize or repaint, still in the process of
                    // loading.
                    return true;
                }
            }
            if (changed != 0) {
                // May need to resize myself, asynchronously:
		safePreferenceChanged();
                return true;
            }

            // Repaint when done or when new pixels arrive:
            if ((flags & (FRAMEBITS|ALLBITS)) != 0) {
                repaint(0);
            }
            else if ((flags & SOMEBITS) != 0 && sIsInc) {
                repaint(sIncRate);
            }
            return ((flags & ALLBITS) == 0);
        }
    }


    /**
     * ImageLabelView is used if the image can't be loaded, and
     * the attribute specified an alt attribute. It overriden a handle of
     * methods as the text is hardcoded and does not come from the document.
     */
    private class ImageLabelView extends InlineView {
        private Segment segment;
        private Color fg;

        ImageLabelView(Element e, String text) {
            super(e);
            reset(text);
        }

        public void reset(String text) {
            segment = new Segment(text.toCharArray(), 0, text.length());
        }

        public void paint(Graphics g, Shape a) {
            // Don't use supers paint, otherwise selection will be wrong
            // as our start/end offsets are fake.
            GlyphPainter painter = getGlyphPainter();

            if (painter != null) {
                g.setColor(getForeground());
                painter.paint(this, g, a, getStartOffset(), getEndOffset());
            }
        }

        public Segment getText(int p0, int p1) {
            if (p0 < 0 || p1 > segment.array.length) {
                throw new RuntimeException("ImageLabelView: Stale view");
            }
            segment.offset = p0;
            segment.count = p1 - p0;
            return segment;
        }

        public int getStartOffset() {
            return 0;
        }
    
        public int getEndOffset() {
            return segment.array.length;
        }

        public View breakView(int axis, int p0, float pos, float len) {
            // Don't allow a break
            return this;
        }

        public Color getForeground() {
            View parent;
            if (fg == null && (parent = getParent()) != null) {
                Document doc = getDocument();
                AttributeSet attr = parent.getAttributes();

                if (attr != null && (doc instanceof StyledDocument)) {
                    fg = ((StyledDocument)doc).getForeground(attr);
                }
            }
            return fg;
        }
    }
}