graphpaneledgestate.java

OpenJGraph是一个开源的Java库

package salvo.jesus.graph.visual;

import salvo.jesus.graph.*;
import java.awt.event.*;
import java.awt.geom.*;
import java.awt.*;

/**
 * State object that represents the edge mode in a GraphPanel.
 * Edge mode being the ability to add an edge interactively by dragging
 * the mouse from a vertex and releasing the mouse on another vertex.
 *
 * @author  Jesus M. Salvo Jr.
 */
public class GraphPanelEdgeState extends GraphPanelState {
    /**
     * Reference to the VisualVertex object selected during the mousePressed() method.
     * This identifies the source vertex of an edge being created.
     */
    VisualVertex    sourcevertex;

    /**
     * Line2D object that is drawn when an edge is being interactively created.
     */
    Line2D.Double         probableedgeline;

    /**
     * A cross-hair Cursor object
     */
    Cursor          edgecursor;

    /**
     * Existing cursor prior to changing the cursor to a cross-hair
     */
    Cursor          previouscursor;

    /**
     * Creates a GraphPanelEdgeState object for the specified GraphPanel object.
     */
    public GraphPanelEdgeState( GraphPanel gpanel ) {
        super( gpanel );
        this.edgecursor = new Cursor( Cursor.CROSSHAIR_CURSOR );
    }

    /**
     * Identifies the source vertex of a new Edge being created.
     */
    public GraphPanelState mousePressed( MouseEvent e ) {
        this.sourcevertex = gpanel.getVisualGraph().getNode( e.getX(), e.getY());

        // Notify the VisualGraphComponent of the event
        informTargetVisualGraphComponentOfMouseEvent(e);

        return this;

    }

    /**
     * Signifies the end of a drag. If there was a vertex clicked during
     * the start of the drag (during the mousePressed() event) and there is
     * a vertex at the end of the drag, then an edge is added to the graph,
     * and the mouse cursor is returned to its original.
     */
    public GraphPanelState mouseReleased( MouseEvent e ) {
        // Edge mode. If there was a vertex clicked during the mousePressed() event
        // and there is a vertex at this (mouseReleased()) event, then add an
        // edge to the graph
        VisualVertex        sinkvertex = null;

        this.probableedgeline = null;
        if( this.sourcevertex != null ) {
            sinkvertex = gpanel.getVisualGraph().getNode( e.getX(), e.getY());
            if( sinkvertex != null )
                try {
                    gpanel.getVisualGraph().addEdge( this.sourcevertex, sinkvertex );
                }
            catch( Exception ex ) {
                ex.printStackTrace();
            }
            this.sourcevertex = null;
        }
        if( this.previouscursor != null ) {
            this.gpanel.setCursor( this.previouscursor );
            this.previouscursor = null;
        }
        gpanel.repaint();

        // Notify the VisualGraphComponent of the event
        informTargetVisualGraphComponentOfMouseEvent(e);

        return this;
    }

    /**
     * If there was a vertex clicked during the start of the drag
     * (during the mousePressed() event), draw a line from the
     * source vertex to the current coordinate.
     */
    public GraphPanelState mouseDragged( MouseEvent e ) {
        // Edge mode. Draw a line between the vertex that was clicked
        // on the mousePressed() event and the current coordinate of the mouse.
        if( this.sourcevertex != null ) {
            if( probableedgeline == null )
                probableedgeline = new Line2D.Double();
            probableedgeline.setLine(
                this.sourcevertex.getBounds().getCenterX(),
                this.sourcevertex.getBounds().getCenterY(),
                (double) e.getX(), (double) e.getY());

            gpanel.repaint();
        }

        // Notify the VisualGraphComponent of the event
        informTargetVisualGraphComponentOfMouseEvent(e);

        return this;
    }

    /**
     * This method sets the cursor to a crosshair whenever the cursor
     * enters a VisualVertex object. The cursor is reset to its original
     * when the mouse cursor leaves a VisualVertex object.
     */
    public GraphPanelState mouseMoved( MouseEvent e ) {
        VisualGraphComponent    vVertex = this.gpanel.getVisualGraph().getNode( e.getX(), e.getY() );
        VisualGraphComponent    vEdge = this.gpanel.getVisualGraph().getVisualEdge( e.getX(), e.getY() );
        VisualGraphComponent    component;

        if( vVertex != null ) {
            if( this.previouscursor == null )
                this.previouscursor = this.gpanel.getCursor();
            this.gpanel.setCursor( this.edgecursor );
        }
        else if( this.previouscursor != null ) {
            this.gpanel.setCursor( this.previouscursor );
            this.previouscursor = null;
        }

        // Notify the VisualGraphComponent of the event
        informTargetVisualGraphComponentOfMouseEvent(e);

        return this;
    }

    /**
     * Call VisualGraph.paint() method, passing the Graphics2D context
     * and the probable edge line to be drawn
     */
    public void paint( Graphics2D g2d ) {
        this.gpanel.getVisualGraph().paint( g2d, this.probableedgeline );
    }

}