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package example; |
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import org.gannacademy.cdf.graphics.Text; |
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import org.gannacademy.cdf.graphics.geom.Path; |
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import org.gannacademy.cdf.graphics.ui.AppWindow; |
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import java.awt.event.MouseEvent; |
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import java.awt.event.MouseListener; |
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import java.awt.geom.AffineTransform; |
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import java.awt.geom.PathIterator; |
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import java.awt.geom.Point2D; |
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public class RotationExample extends AppWindow implements MouseListener { |
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private static final double |
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BASE = 50, |
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HEIGHT = 100, |
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THETA = Math.PI / 180.0; |
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private Path path; |
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private double x, y; |
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private boolean mouseDown; |
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private int button; |
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@Override |
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protected void setup() { |
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// show instructions to user |
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new Text("Left, middle, or right-click to rotate the triangle", 10, 40, getDrawingPanel()); |
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x = getDrawingPanel().getWidth() / 2.0; |
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// calculate top point of triangle |
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y = (getDrawingPanel().getHeight() - HEIGHT) / 2.0; |
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// define the triangle path |
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path = new Path(getDrawingPanel()); |
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path.moveTo(x, y); // move to top point |
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path.lineTo(x + BASE / 2.0, y + HEIGHT); // line to bottom-right point |
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path.lineTo(x - BASE / 2.0, y + HEIGHT); // line to bottom-left point |
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path.lineTo(x, y); // line back to top point |
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// register to be notified of mouse events (and assume no one is clicking right now) |
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mouseDown = false; |
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getDrawingPanel().addMouseListener(this); |
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getDrawingPanel().requestFocus(); |
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} |
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@Override |
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protected void loop() { |
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if (mouseDown) { |
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double theta = THETA; // default, rotate clockwise around mouse |
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double x = this.x, y = this.y; // default, use whatever (x, y) is currently set for axis of rotation |
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if (button == MouseEvent.BUTTON1) theta *= -1; // left button, rotate counter-clockwise around mouse |
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else if (button == MouseEvent.BUTTON2) { // middle button, rotate around center of gravity |
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// use center of gravity calculation as rotation axis |
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Point2D center = getCenterOfGravity(); |
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x = center.getX(); |
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y = center.getY(); |
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} |
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// rotate, using any adjustments to theta and axis of rotiation |
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path.transform(AffineTransform.getRotateInstance(theta, x, y)); |
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} |
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sleep(25); |
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} |
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public Point2D getCenterOfGravity() { |
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PathIterator i = path.getPathIterator(null); |
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double[] coords = new double[6]; // to hold coordinates |
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double x = 0, y = 0; // tally x and y-coordinates |
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int points = 0; // haven't visited any points yet |
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while (!i.isDone()) { |
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if (points != 0) { // skip the first visit to the top point |
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i.currentSegment(coords); |
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x += coords[0]; |
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y += coords[1]; |
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} |
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i.next(); |
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if (!i.isDone()) points++; // don't double-count last point! |
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} |
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// package (x, y) coordinates into a single object |
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return new Point2D.Double(x / points, y / points); |
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} |
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@Override |
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public void mouseClicked(MouseEvent e) { |
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} |
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@Override |
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public void mousePressed(MouseEvent e) { |
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mouseDown = true; |
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button = e.getButton(); |
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x = e.getX(); |
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y = e.getY(); |
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} |
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@Override |
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public void mouseReleased(MouseEvent e) { |
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mouseDown = false; |
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} |
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@Override |
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public void mouseEntered(MouseEvent e) { |
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} |
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@Override |
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public void mouseExited(MouseEvent e) { |
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} |
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public static void main(String[] args) { |
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new RotationExample(); |
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} |
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} |
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gann-cdf /
graphics
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