Source code for LayeredPanel.java

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package layers;

import java.awt.AlphaComposite;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import java.awt.event.MouseMotionListener;
import java.awt.image.BufferedImage;
import java.util.LinkedList;
import java.util.ListIterator;
import javax.swing.JPanel;

/**
 *
 * @author pat
 */
public class LayeredPanel extends JPanel implements MouseListener, MouseMotionListener {

    LinkedList<Layer> layers = new LinkedList<Layer>();
    Layer active = null;
    BufferedImage layer_output;

    public LayeredPanel() {
        this.addMouseListener(this);
        this.addMouseMotionListener(this);
    }

    
    public void setNoActiveLayer() {
        active=null;
        repaint();
    }
    
    public void setActiveLayer(Layer l) {
        active = l;
        repaint();
    }

    /**
     * Add a layer which draws after all other layers.
     */
    public void addTopLayer(Layer l) {
        layers.addLast(l);
        this.repaintAllLayers();
    }

    /**
     * Add a layer which draws before all previous layers.
     */
    public void addBottomLayer(Layer l) {
        layers.addFirst(l);
        this.repaintAllLayers();
    }

    public void removeLayer(Layer l) {
        layers.remove(l);
        this.repaintAllLayers();
    }

    public void moveActiveToBottom() {
        moveLayerToBottom(active);
    }

    public void moveLayerToBottom(Layer l) {
        layers.remove(l);
        addBottomLayer(l);
        this.repaintAllLayers();
    }

    public void moveActiveToTop() {
        moveLayerToTop(active);
    }

    public void moveLayerToTop(Layer l) {
        layers.remove(l);
        addTopLayer(l);
        this.repaintAllLayers();
    }

    public void moveActiveLayerUp() {
        moveLayerUp(active);
    }

    public void moveLayerUp(Layer l) {
        ListIterator<Layer> it = layers.listIterator();
        Layer last = null;
        while ((it.hasNext()) && (last != l)) {
            last = it.next();
        }
        if ((last == l) && (it.hasNext())) {
            it.remove();
            it.next();
            it.add(l);
            this.repaintAllLayers();
        }
    }

    public void moveActiveLayerDown() {
        moveLayerDown(active);        
    }

    public void moveLayerDown(Layer l) {
        ListIterator<Layer> it = layers.listIterator(layers.size());
        Layer last = null;
        while ((it.hasPrevious()) && (last != l)) {
            last = it.previous();
        }
        if ((last == l) && (it.hasPrevious())) {
            it.remove();
            it.previous();
            it.add(l);
            this.repaintAllLayers();
        }
    }

    public void repaintAllLayers() {
        layer_output = null;
        repaint();
    }

    @Override
    protected void paintComponent(Graphics grphcs) {
        super.paintComponent(grphcs);

        if ((layer_output == null) || (layer_output.getWidth() != getWidth()) || (layer_output.getHeight() != getHeight())) {
            layer_output = new BufferedImage(getWidth(), getHeight(),
                    BufferedImage.TYPE_INT_ARGB);
            Graphics2D imgG = layer_output.createGraphics();
            imgG.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON); // Anti-aliasing looks pretty!
            imgG.setComposite(AlphaComposite.Clear);
            imgG.fillRect(0, 0, getWidth(), getHeight());
            imgG.setComposite(AlphaComposite.SrcOver);

            for (Layer l : layers) {
                l.render(imgG);
            }
            imgG.dispose();
        }

        Graphics2D g = (Graphics2D) grphcs; // Better to draw with a Graphics2D object.
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                RenderingHints.VALUE_ANTIALIAS_ON); // Anti-aliasing looks pretty!

        g.drawImage(layer_output, 0, 0, this);

        if (active != null) {
            active.renderActive(g);
        }

    }

    // Mouse handling:
    public void mouseClicked(MouseEvent me) {
        if (active != null) {
            active.mouseClicked(me);
        }
    }

    public void mouseEntered(MouseEvent me) {
        if (active != null) {
            active.mouseEntered(me);
        }
    }

    public void mouseExited(MouseEvent me) {
        if (active != null) {
            active.mouseExited(me);
        }
    }

    public void mousePressed(MouseEvent me) {
        if (active != null) {
            active.mousePressed(me);
        }
    }

    public void mouseReleased(MouseEvent me) {
        if (active != null) {
            active.mouseReleased(me);
        }
    }

    public void mouseDragged(MouseEvent me) {
        if (active != null) {
            active.mouseDragged(me);
        }
    }

    public void mouseMoved(MouseEvent me) {
        if (active != null) {
            active.mouseMoved(me);
        }
    }
}

Last modified on August 17, 2018.