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| 1 | +package ch_15; |
| 2 | + |
| 3 | +import javafx.application.Application; |
| 4 | +import javafx.beans.property.SimpleStringProperty; |
| 5 | +import javafx.beans.property.StringProperty; |
| 6 | +import javafx.geometry.Pos; |
| 7 | +import javafx.scene.Scene; |
| 8 | +import javafx.scene.control.Button; |
| 9 | +import javafx.scene.layout.BorderPane; |
| 10 | +import javafx.scene.layout.Pane; |
| 11 | +import javafx.scene.paint.Color; |
| 12 | +import javafx.scene.shape.Line; |
| 13 | +import javafx.stage.Stage; |
| 14 | + |
| 15 | +import java.util.ArrayList; |
| 16 | +import java.util.List; |
| 17 | + |
| 18 | +/** |
| 19 | + * ***15.35 (Animation: self-avoiding random walk) Revise the preceding exercise to display |
| 20 | + * the walk step by step in an animation, as shown in Figure 15.37c and d. |
| 21 | + */ |
| 22 | +public class Exercise15_35 extends Application { |
| 23 | + private double paneWidth = 300; |
| 24 | + private double paneHeight = 250; |
| 25 | + private StringProperty buttonLabel = new SimpleStringProperty("Start"); |
| 26 | + |
| 27 | + @Override |
| 28 | + public void start(Stage primaryStage) { |
| 29 | + Lattice lattice = new Lattice(); |
| 30 | + BorderPane borderPane = new BorderPane(); |
| 31 | + borderPane.setCenter(lattice); |
| 32 | + Button btStart = new Button(); |
| 33 | + btStart.textProperty().bind(buttonLabel); |
| 34 | + btStart.setOnAction(e -> lattice.actionButtonPressed()); |
| 35 | + borderPane.setBottom(btStart); |
| 36 | + BorderPane.setAlignment(btStart, Pos.CENTER); |
| 37 | + |
| 38 | + Scene scene = new Scene(borderPane, paneWidth, paneHeight + 40); |
| 39 | + primaryStage.setTitle(getClass().getName()); |
| 40 | + primaryStage.setScene(scene); |
| 41 | + primaryStage.show(); |
| 42 | + } |
| 43 | + |
| 44 | + class Lattice extends Pane { |
| 45 | + public static final int N = 16; |
| 46 | + private Point[][] lattice = new Point[N + 1][N + 1]; |
| 47 | + private double hGap = paneWidth / N; |
| 48 | + private double vGap = paneHeight / N; |
| 49 | + |
| 50 | + private List<Line> steps = new ArrayList<>(); |
| 51 | + private int stepIndex = 0; |
| 52 | + |
| 53 | + public Lattice() { |
| 54 | + drawGrid(); |
| 55 | + } |
| 56 | + |
| 57 | + /** |
| 58 | + * Draw lines |
| 59 | + */ |
| 60 | + public void drawGrid() { |
| 61 | + // Draw lattice lines |
| 62 | + for (int i = 1; i < N + 1; i++) { |
| 63 | + Line line1 = new Line(0, i * vGap, paneWidth, i * vGap); |
| 64 | + Line line2 = new Line(i * hGap, 0, i * hGap, paneHeight); |
| 65 | + this.getChildren().addAll(line1, line2); |
| 66 | + line1.setStroke(Color.LIGHTGRAY); |
| 67 | + line2.setStroke(Color.LIGHTGRAY); |
| 68 | + } |
| 69 | + } |
| 70 | + |
| 71 | + /** |
| 72 | + * Build the steps of the path and store in a Line array |
| 73 | + */ |
| 74 | + public void createPathSteps() { |
| 75 | + getChildren().clear(); |
| 76 | + drawGrid(); |
| 77 | + |
| 78 | + // Start from the center point in the lattice (i, j) |
| 79 | + int i = (N + 1) / 2; |
| 80 | + int j = (N + 1) / 2; |
| 81 | + |
| 82 | + while (lattice[i][j] != null) { |
| 83 | + Point p = lattice[i][j]; |
| 84 | + Line line = new Line(i * hGap, j * vGap, p.x * hGap, p.y * vGap); |
| 85 | + steps.add(line); |
| 86 | + i = p.x; |
| 87 | + j = p.y; |
| 88 | + } |
| 89 | + } |
| 90 | + |
| 91 | + void drawNextStep() { |
| 92 | + if (stepIndex == 0) { |
| 93 | + buttonLabel.setValue("Next"); |
| 94 | + } |
| 95 | + |
| 96 | + if (stepIndex < steps.size()) { |
| 97 | + getChildren().add(steps.get(stepIndex++)); |
| 98 | + } else { |
| 99 | + buttonLabel.setValue("Restart"); |
| 100 | + } |
| 101 | + } |
| 102 | + |
| 103 | + public void getAPath() { |
| 104 | + // Refresh lattice |
| 105 | + for (int i = 0; i < lattice.length; i++) { |
| 106 | + for (int j = 0; j < lattice.length; j++) { |
| 107 | + lattice[i][j] = null; |
| 108 | + } |
| 109 | + } |
| 110 | + |
| 111 | + // (i, j) is the current path point. Initially it is at the center |
| 112 | + int i = (N + 1) / 2; |
| 113 | + int j = (N + 1) / 2; |
| 114 | + |
| 115 | + while (i > 0 && i < N && j > 0 && j < N) { |
| 116 | + if (lattice[i - 1][j] != null && lattice[i + 1][j] != null |
| 117 | + && lattice[i][j - 1] != null && lattice[i][j + 1] != null) { |
| 118 | + break; // Dead end |
| 119 | + } |
| 120 | + |
| 121 | + double r = Math.random(); |
| 122 | + if (r < .25 && lattice[i][j + 1] == null) { |
| 123 | + lattice[i][j] = new Point(i, j + 1); // Right |
| 124 | + j++; |
| 125 | + } else if (r < .50 && lattice[i + 1][j] == null) { |
| 126 | + lattice[i][j] = new Point(i + 1, j); // Down |
| 127 | + i++; |
| 128 | + } else if (r < .75 && lattice[i][j - 1] == null) { |
| 129 | + lattice[i][j] = new Point(i, j - 1); // Left |
| 130 | + j--; |
| 131 | + } else if (r < 1.00 && lattice[i - 1][j] == null) { |
| 132 | + lattice[i][j] = new Point(i - 1, j); // Up |
| 133 | + i--; |
| 134 | + } |
| 135 | + } |
| 136 | + |
| 137 | + createPathSteps(); |
| 138 | + } |
| 139 | + |
| 140 | + public void actionButtonPressed() { |
| 141 | + if (buttonLabel.getValue().equals("Start")) { |
| 142 | + getAPath(); |
| 143 | + drawNextStep(); |
| 144 | + } else if (buttonLabel.getValue().equals("Next")) { |
| 145 | + drawNextStep(); |
| 146 | + } else if (buttonLabel.getValue().equals("Restart")) { |
| 147 | + getChildren().clear(); |
| 148 | + steps.clear(); |
| 149 | + stepIndex = 0; |
| 150 | + drawGrid(); |
| 151 | + buttonLabel.setValue("Start"); |
| 152 | + } |
| 153 | + } |
| 154 | + |
| 155 | + class Point { |
| 156 | + int x; |
| 157 | + int y; |
| 158 | + |
| 159 | + Point(int i, int j) { |
| 160 | + this.x = i; |
| 161 | + this.y = j; |
| 162 | + } |
| 163 | + } |
| 164 | + } |
| 165 | + |
| 166 | +} |
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