hittestsample.java

JSP中文介绍,对于菜鸟有用

import java.awt.Color;
import java.awt.Component;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Shape;
import java.awt.font.FontRenderContext;
import java.awt.font.TextHitInfo;
import java.awt.font.TextLayout;
import java.awt.geom.Point2D;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.text.AttributedCharacterIterator;

/**
 * This class demonstrates how to hit-test a TextLayout.  Hit-testing
 * is the mapping of a graphical location to a character position within
 * text.
 *
 * This class constructs a TextLayout from an AttributedCharacterIterator
 * and displays the TextLayout.  When the mouse is clicked inside this
 * Component, the mouse position is mapped to a character position, and the
 * carets for this character position are displayed.
 */
public class HitTestSample extends Component {

    // Colors to use for the strong and weak carets.
    private static final Color STRONG_CARET_COLOR = Color.red;
    private static final Color WEAK_CARET_COLOR = Color.black;

    // The TextLayout to draw and hit-test.
    private TextLayout textLayout;

    // The insertion index of the most recent mouse click.
    private int insertionIndex;

    public HitTestSample(AttributedCharacterIterator text) {

        FontRenderContext frc = SampleUtils.getDefaultFontRenderContext();

        // Create a new TextLayout from the given text.
        textLayout = new TextLayout(text, frc);

        // Initilize insertionIndex.
        insertionIndex = 0;

        addMouseListener(new HitTestMouseListener());
    }

    /**
     * Compute a location within this Component for textLayout's origin,
     * such that textLayout is centered horizontally and vertically.
     *
     * Note that this location is unknown to textLayout;  it is used only
     * by this Component for positioning.
     */
    private Point2D computeLayoutOrigin() {

        Dimension size = getSize();
        
        Point2D.Float origin = new Point2D.Float();

        origin.x = (float) (size.width - textLayout.getAdvance()) / 2;
        origin.y = (float) (size.height - textLayout.getDescent() + textLayout.getAscent()) / 2;

        return origin;
    }

    /**
     * Draw textLayout and the carets corresponding to the most recent
     * mouse click (if any).
     */
    public void paint(Graphics g) {

        Graphics2D graphics2D = (Graphics2D) g;

        Point2D origin = computeLayoutOrigin();

        // Since the caret Shapes are relative to the origin 
        // of textLayout, we'll translate the graphics so that 
        // the origin of the graphics is where we want textLayout
        // to appear.

        graphics2D.translate(origin.getX(), origin.getY());

        // Draw textLayout.
        textLayout.draw(graphics2D, 0, 0);

        // Retrieve caret Shapes for insertionIndex.
        Shape[] carets = textLayout.getCaretShapes(insertionIndex);

        // Draw the carets.  carets[0] is the strong caret, and
        // is never null.  carets[1], if it is not null, is the
        // weak caret.
        graphics2D.setColor(STRONG_CARET_COLOR);
        graphics2D.draw(carets[0]);

        if (carets[1] != null) {
            graphics2D.setColor(WEAK_CARET_COLOR);
            graphics2D.draw(carets[1]);
        }
    }

    private class HitTestMouseListener extends MouseAdapter {

        /**
         * Compute the character position of the mouse click.
         */
        public void mouseClicked(MouseEvent e) {

            Point2D origin = computeLayoutOrigin();

            // Compute the mouse click location relative to
            // textLayout's origin.
            float clickX = (float) (e.getX() - origin.getX());
            float clickY = (float) (e.getY() - origin.getY());

            // Get the character position of the mouse click.
            TextHitInfo currentHit = textLayout.hitTestChar(clickX, clickY);
            insertionIndex = currentHit.getInsertionIndex();

            // Repaint the Component so the new caret(s) will be displayed.
            repaint();
        }
    }

    public static void main(String[] args) {

        AttributedCharacterIterator text = SampleUtils.getText(args);

        Component sample = new HitTestSample(text);
        SampleUtils.showComponentInFrame(sample, "Hit Test Sample");
    }
}