## Saturday, 24 December 2016

### Chapter 14 Exercise 20, Introduction to Java Programming, Tenth Edition Y. Daniel LiangY.

14.20 (Draw an arrow line) Write a static method that draws an arrow
line from a start- ing point to an ending point in a pane using the
public static void drawArrowLine(double startX, double startY, double endX, double endY, Pane pane)

Programming Exercises 581
Write a test program that randomly draws an arrow line, as shown in Figure 14.49a.
import javafx.collections.ObservableList;
import javafx.geometry.Point2D;
import javafx.scene.Node;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Line;
import javafx.scene.text.Text;

import java.util.ArrayList;
public class PaneCollection {

public static void drawArrowLine(double x1, double y1, double x2,   double y2, Pane pane) {
drawArrowLine(x1, y1, x2, y2, pane, 15);
}

public static void drawArrowLine(double x1, double y1, double x2,   double y2, Pane pane, int length) {
drawArrowLine(new Line(x1, y1, x2, y2), pane, length);
}

public static void drawArrowLine(Line line, Pane pane) {
drawArrowLine(line, pane, 15);
}

public static void drawArrowLine(Line line, Pane pane, int length) {
ObservableList<Node> list = pane.getChildren();

double arctan = Math.atan(slope(line));
double set45 = (line.getStartX() > line.getEndX()) ? 1.57 / 2 : -1.57 * 1.5;

(line.getEndX() + Math.cos(arctan - set45) * length),
(line.getEndY() + Math.sin(arctan - set45) * length)));
(line.getEndX() + Math.cos(arctan + set45) * length),
(line.getEndY() + Math.sin(arctan + set45) * length)));
}

public static double slope(Line line) {
return (line.getStartY() - line.getEndY()) / (line.getStartX() - line.getEndX());
}

public static double distance(double x1, double y1, double x2, double y2) {

return Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2));
}

public static double distance(Line line) {
return distance(line.getStartX(), line.getStartY(), line.getEndX(), line.getEndY());
}

public static MyPoint getCenterPoint(Line line) {

return new MyPoint(
(line.getStartX() + line.getEndX()) / 2,
(line.getStartY() + line.getEndY()) / 2);
}

public static void drawPointCounter(Pane pane, Point2D[] points) {
int counter = 1;

for (Point2D point : points) {
Circle temp = new Circle(point.getX(), point.getY(), 5, Color.TRANSPARENT);
Text text = new Text(point.getX(), point.getY(), "" + counter++);
}
}

public static boolean containsPoint(ArrayList<Point2D> points, double x, double y) {
for (Point2D p : points) {
if (p.getX() == x && p.getY() == y) return true;
}
return false;
}

public static boolean removePoint(ArrayList<Point2D> points, double x, double y) {

int index = 0;
for (Point2D p : points) {
if (p.getX() == x && p.getY() == y) {
points.remove(index);
return true;
}
index++;
}
return false;
}

public static Line copyLine(Line l) {
return new Line(l.getStartX(), l.getStartY(), l.getEndX(), l.getEndY());
}

}


import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.layout.Pane;
import javafx.scene.shape.Line;
import javafx.stage.Stage;

public class Exercise_20 extends Application {

@Override
public void start(Stage primaryStage) throws Exception {

Pane pane = new Pane();
double width = 400;
double height = 400;
Line line = new Line(
Math.random() * width,
Math.random() * height,
Math.random() * width,
Math.random() * height);

PaneCollection.drawArrowLine(line,pane);
primaryStage.setTitle("Draw Random arrow");
primaryStage.setScene(new Scene(pane, width, height));
primaryStage.show();
}

public static void main(String[] args) {

Application.launch(args);

}
}