GRAPHS AND APPLICATIONS - Introduction to Java Programming: Comprehensive Version - page 1035

L ISTING 28.6

GraphView.java
1 import javafx.scene.layout.Pane;
2 import javafx.scene.shape.Circle;
3 import javafx.scene.shape.Line;
4 import javafx.scene.text.Text;
5
6 public class GraphView extends Pane {
7

extends Pane
Displayable vertices private Graph<? extends Displayable> graph;

8
9 public GraphView(Graph<? extends Displayable> graph) {

10 this .graph = graph;

11
12 // Draw vertices
13 java.util.List<? extends Displayable> vertices
14 = graph.getVertices();
15 for ( int i = 0 ; i < graph.getSize(); i++) {
16 int x = vertices.get(i).getX();
17 int y = vertices.get(i).getY();
18 String name = vertices.get(i).getName();
19
20 getChildren().add( new Circle(x, y, 16 )); // Display a vertex display a vertex

display a text 21 getChildren().add( new Text(x - 8 , y - 18 , name));

22 }
23
24 // Draw edges for pairs of vertices
25 for ( int i = 0 ; i < graph.getSize(); i++) {
26 java.util.List<Integer> neighbors = graph.getNeighbors(i);
27 int x1 = graph.getVertex(i).getX();

28 int y1 = graph.getVertex(i).getY();

29 for ( int v: neighbors) {

30 int x2 = graph.getVertex(v).getX();

31 int y2 = graph.getVertex(v).getY();

32
33 // Draw an edge for (i, v)

34 getChildren().add( new Line(x1, y1, x2, y2));

draw an edge

35 }
36 }
37 }
38 }

To display a graph on a pane, simply create an instance of GraphView by passing the
graph as an argument in the constructor (line 9). The class for the graph's vertex must imple-
ment the Displayable interface in order to display the vertices (lines 13-22). For each
vertex index i , invoking graph.getNeighbors(i) returns its adjacency list (line 26). From
this list, you can find all vertices that are adjacent to i and draw a line to connect i with its
adjacent vertex (lines 27-34).
Listing 28.7 gives an example of displaying the graph in Figure 28.1, as shown in
Figure 28.10.

L ISTING 28.7

DisplayUSMap.java
1 import javafx.application.Application;
2 import javafx.scene.Scene;
3 import javafx.stage.Stage;
4
5 public class DisplayUSMap extends Application {
6 @Override // Override the start method in the Application class
7 public void start(Stage primaryStage) {
8 City[] vertices = { new City( "Seattle" , 75 , 50 ),