layermanager.java

J2me唆哈的代码

/*
 * Created on 2005-12-20 by pcy
 *
 * TODO To change the template for this generated file go to
 * Window - Preferences - Java - Code Style - Code Templates
 */
package javax.microedition.lcdui.game;

import javax.microedition.lcdui.Graphics;

public class LayerManager {

    /**
     * The number of layers in this LayerManager. This value can be null.
     */
    private int nlayers; // = 0;

    /**
     * The Layers in this LayerManager.
     * 
     * @see #append(Layer)
     */
    private Layer component[] = new Layer[4];

    /**
     * the view window co-ordinates.
     */
    private int viewX, viewY, viewWidth, viewHeight; // = 0;

    public LayerManager() {
        setViewWindow(0, 0, Integer.MAX_VALUE, Integer.MAX_VALUE);
    }

    public void append(Layer l) {
        removeImpl(l);
        addImpl(l, nlayers);
    }

    public void insert(Layer l, int index) {
        /* Check for correct arguments: index in bounds */
        if ((index < 0) || (index > nlayers)) {
            throw new IndexOutOfBoundsException();
        }
        // if the Layer is already present
        // remove it
        // will throw NullPointerException if the Layer is null
        removeImpl(l);
        // insert it at the specified index
        addImpl(l, index);
    }

    public Layer getLayerAt(int index) {
        if ((index < 0) || (index >= nlayers)) {
            throw new IndexOutOfBoundsException();
        }
        return component[index];
    }

    public int getSize() {
        return nlayers;
    }

    public void remove(Layer l) {
        removeImpl(l);
    }

    public void paint(Graphics g, int x, int y) {

        // if g == null g.getClipX will throw NullPointerException;

        // save the original clip
        int clipX = g.getClipX();
        int clipY = g.getClipY();
        int clipW = g.getClipWidth();
        int clipH = g.getClipHeight();

        // translate the LayerManager co-ordinates to Screen co-ordinates
        g.translate(x - viewX, y - viewY);
        // set the clip to view window
        g.clipRect(viewX, viewY, viewWidth, viewHeight);

        // draw last to first
        for (int i = nlayers; --i >= 0;) {
            Layer comp = component[i];
            if (comp.visible) {
                // REMINDER: do this if outside Graphics clip region don't paint
                // (comp.contains(x - comp.x, y - comp.y)) &&
                // paint will happen only in clipped region of view window
                comp.paint(g);
            }
        }

        g.translate(-x + viewX, -y + viewY);
        g.setClip(clipX, clipY, clipW, clipH);
    }

    public void setViewWindow(int x, int y, int width, int height) {

        if (width < 0 || height < 0) {
            throw new IllegalArgumentException();
        }

        viewX = x;
        viewY = y;
        viewWidth = width;
        viewHeight = height;
    }

    private void addImpl(Layer layer, int index) {
        // Add component to list;
        // allocate new array if necessary.

        if (nlayers == component.length) {
            Layer newcomponents[] = new Layer[nlayers + 4];
            System.arraycopy(component, 0, newcomponents, 0, nlayers);
            System.arraycopy(component, index, newcomponents, index + 1,
                    nlayers - index);
            component=null;
            component = newcomponents;
        } else {
            System.arraycopy(component, index, component, index + 1, nlayers
                    - index);
        }
        component[index] = layer;
        ++nlayers;
    }

    private void removeImpl(Layer l) {
        if (l == null) {
            throw new NullPointerException();
        }
        for (int i = nlayers; --i >= 0;) {
            if (component[i] == l) {
                remove(i);
            }
        }
    }

    private void remove(int index) {
        System.arraycopy(component, index + 1, component, index, nlayers
                - index - 1);
        component[--nlayers] = null;
    }

}