Astar pathfinding in a grid

This commit is contained in:
Thibaud Gasser 2018-09-29 19:05:19 +02:00
parent 12dfbbc705
commit 41c9bdb1f3
7 changed files with 373 additions and 0 deletions

14
pom.xml
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@ -24,6 +24,20 @@
</build> </build>
<modules> <modules>
<module>clock</module> <module>clock</module>
<module>simple-pathfinding</module>
</modules> </modules>
<dependencies>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>RELEASE</version>
</dependency>
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-simple</artifactId>
<version>RELEASE</version>
</dependency>
</dependencies>
</project> </project>

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns="http://maven.apache.org/POM/4.0.0"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>swingapps</artifactId>
<groupId>fr.uha.gasser</groupId>
<version>1.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>simple-pathfinding</artifactId>
</project>

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package fr.uha.gasser.pathfinding.algorithm;
import java.awt.*;
import java.util.*;
import java.util.List;
class AStarSearch {
private final Node start;
private final Node goal;
AStarSearch(Node start, Node goal) {
this.start = start;
this.goal = goal;
}
private Node search() {
PriorityQueue<Node> frontier = new PriorityQueue<>();
Set<Node> explored = new HashSet<>();
frontier.add(start);
while (!frontier.isEmpty()) {
Node currentNode = frontier.poll();
explored.add(currentNode);
if (currentNode.getLoc().equals(goal.getLoc())) {
return currentNode;
}
for (Node neighbor : getNeighbors(currentNode)) {
// Ignore the neighbor which is already evaluated.
if (explored.contains(neighbor)) continue;
if (!frontier.contains(neighbor)) {
neighbor.setParent(currentNode);
neighbor.cost++;
neighbor.hValue = neighbor.cost + neighbor.loc.distance(goal.loc);
frontier.add(neighbor);
}
}
}
return null;
}
List<Node> shortestPath() {
Node currentNode = search();
LinkedList<Node> path = new LinkedList<>();
while (currentNode.getParent() != null) {
path.addFirst(currentNode);
currentNode = currentNode.getParent();
}
return path;
}
private List<Node> getNeighbors(Node current) {
LinkedList<Node> neighbors = new LinkedList<>();
for (Direction direction : Direction.values()) {
neighbors.add(getNeighbor(current, direction));
}
return neighbors;
}
private Node getNeighbor(Node current, Direction direction) {
Node node = new Node(current);
node.setLoc(new Point(current.loc.x + direction.x, current.loc.y + direction.y));
return node;
}
private enum Direction {
UP(0, 1),
DOWN(0, -1),
LEFT(-1, 0),
LEFT_UP(-1, 1),
LEFT_DOWN(-1, -1),
RIGHT(1, 0),
RIGHT_UP(1, 1),
RIGHT_DOWN(1, -1);
public final int x;
public final int y;
Direction(int x, int y) {
this.x = x;
this.y = y;
}
}
}

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package fr.uha.gasser.pathfinding.algorithm;
import fr.uha.gasser.pathfinding.ui.Grid;
import javax.swing.*;
import java.awt.*;
import java.util.List;
public class AStarWorker extends SwingWorker<List<Node>, List<Node>> {
private final Node start;
private final Node goal;
private final Grid target;
private List<Node> path;
public AStarWorker(Node start, Node goal, Grid target) {
this.start = start;
this.goal = goal;
this.target = target;
}
@Override
protected List<Node> doInBackground() throws Exception {
AStarSearch aStar = new AStarSearch(start, goal);
path = aStar.shortestPath();
return path;
}
@Override
protected void done() {
if (this.isCancelled()) return;
path.forEach(node -> {
if (! node.loc.equals(goal.loc)) target.setTile(node.loc, Color.BLUE);
});
}
}

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package fr.uha.gasser.pathfinding.algorithm;
import java.awt.*;
public class Node implements Comparable<Node> {
private Node parent;
Point loc;
int cost;
double hValue; // heuristic value
public Node(Point loc) {
this.loc = loc;
}
Node(Node other) {
this.parent = other.parent;
this.loc = other.loc;
this.cost = other.cost;
this.hValue = other.hValue;
}
void setParent(Node parent) {
this.parent = parent;
}
public void sethValue(double hValue) {
this.hValue = hValue;
}
void setLoc(Point point) {
this.loc = point;
}
public Point getLoc() {
return loc;
}
Node getParent() {
return parent;
}
@Override
public int compareTo(Node other) {
return Double.compare(this.hValue, other.hValue);
}
}

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package fr.uha.gasser.pathfinding.ui;
import fr.uha.gasser.pathfinding.algorithm.AStarWorker;
import fr.uha.gasser.pathfinding.algorithm.Node;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import javax.swing.*;
import java.awt.*;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
public class App extends JFrame {
private static final int ROWS = 30;
private static final int COLS = 30;
private static final int CELL_SIZE = 16;
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
private final Grid grid;
private AStarWorker pathfinder;
private Node startNode;
private Node endNode;
private JPanel gridPane;
private App() throws HeadlessException {
super("Pathfinding");
grid = new Grid(ROWS, COLS, CELL_SIZE);
setupInterface();
pack();
setVisible(true);
}
private void setupInterface() {
gridPane = new JPanel();
gridPane.setLayout(new GridLayout(ROWS, COLS));
for (JLabel label : grid) {
gridPane.add(label);
}
gridPane.addMouseListener(new MouseAdapter() {
@Override
public void mousePressed(MouseEvent e) {
final JLabel at = (JLabel) gridPane.getComponentAt(e.getPoint());
final Point loc = grid.findLoc(at);
if (startNode == null) {
grid.setTile(loc, Color.RED);
startNode = new Node(loc);
} else if (endNode == null) {
grid.setTile(loc, Color.GREEN);
endNode = new Node(loc);
}
}
});
final JMenuBar menuBar = new JMenuBar();
final JMenuItem runItem = new JMenuItem("Run");
menuBar.add(runItem);
runItem.addActionListener(actionEvent -> doSearch());
final JMenuItem cancelItem = new JMenuItem("Cancel");
menuBar.add(cancelItem);
cancelItem.addActionListener(actionEvent -> doCancel());
final JMenuItem resetItem = new JMenuItem("Reset");
menuBar.add(resetItem);
resetItem.addActionListener(actionEvent -> doReset());
setJMenuBar(menuBar);
getContentPane().add(gridPane);
}
private void doReset() {
pathfinder = null;
startNode = null;
endNode = null;
grid.clear();
}
private void doCancel() {
if (pathfinder == null) return;
pathfinder.cancel(true);
}
private void doSearch() {
pathfinder = new AStarWorker(startNode, endNode, grid);
pathfinder.execute();
}
public static void main(String[] args) {
EventQueue.invokeLater(App::new);
}
}

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package fr.uha.gasser.pathfinding.ui;
import javax.swing.*;
import javax.swing.border.Border;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.util.Iterator;
public class Grid implements Iterable<JLabel> {
private final static Border lineBorder = BorderFactory.createLineBorder(Color.BLACK, 1);
private final JLabel[] cells;
private final Dimension size;
private int cellSize;
Grid(int rows, int cols, int cellSize) {
this.cellSize = cellSize;
this.size = new Dimension(rows, cols);
int size = rows * cols;
this.cells = new JLabel[size];
initGrid(size);
}
private void initGrid(int size) {
for (int i = 0; i < size; i++) {
final JLabel label = new JLabel();
// Force cell size
label.setPreferredSize(new Dimension(cellSize, cellSize));
label.setMinimumSize(label.getPreferredSize());
label.setMaximumSize(label.getPreferredSize());
label.setBorder(lineBorder);
label.setOpaque(true);
cells[i] = label;
}
}
public Point findLoc(JLabel cell) {
for (int i = 0; i < cells.length; i++) {
JLabel label = cells[i];
if (cell == label) return new Point(i % size.width, i / size.height);
}
// Not found
return new Point(-1, -1);
}
public void setTile(Point loc, Color color) {
setTile(loc.x + size.width*loc.y, color);
}
private void setTile(int index, Color color) {
final JLabel label = cells[index];
label.setBackground(color);
label.revalidate();
}
void clear() {
for (JLabel cell : cells) {
cell.setBackground(null);
}
}
@Override
public Iterator<JLabel> iterator() {
return new Iterator<>() {
private int pos = 0;
@Override
public boolean hasNext() {
return cells.length > pos;
}
@Override
public JLabel next() {
return cells[pos++];
}
};
}
}