结队作业-地铁查询作业(5)

建立SQLite数据库

java
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public class DatabaseHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "subway.db";
    private static final int DATABASE_VERSION = 1;

    public DatabaseHelper(Context context) {
        super(context, DATABASE_NAME, null, DATABASE_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db) {
        db.execSQL("CREATE TABLE stations (_id INTEGER PRIMARY KEY, name TEXT NOT NULL, line_id INTEGER NOT NULL);");
        db.execSQL("CREATE TABLE lines (_id INTEGER PRIMARY KEY, name TEXT NOT NULL, color TEXT NOT NULL);");
        db.execSQL("CREATE TABLE station_lines (_id INTEGER PRIMARY KEY, station_id INTEGER NOT NULL, line_id INTEGER NOT NULL, FOREIGN KEY (station_id) REFERENCES stations (_id), FOREIGN KEY (line_id) REFERENCES lines (_id));");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        db.execSQL("DROP TABLE IF EXISTS stations;");
        db.execSQL("DROP TABLE IF EXISTS lines;");
        db.execSQL("DROP TABLE IF EXISTS station_lines;");
        onCreate(db);
    }
}

查询路径

java
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public class PathFinder {
    private static final int INFINITY = Integer.MAX_VALUE;
    private Graph graph;
    private int[] distTo;
    private boolean[] marked;
    private Edge[] edgeTo;
    private PriorityQueue<Station> pq;

    public PathFinder(Graph graph) {
        this.graph = graph;
    }

    public void findPath(Station start, Station end) {
        distTo = new int[graph.getNumVertices()];
        marked = new boolean[graph.getNumVertices()];
        edgeTo = new Edge[graph.getNumVertices()];
        pq = new PriorityQueue<>(graph.getNumVertices());

        for (int v = 0; v < graph.getNumVertices(); v++) {
            distTo[v] = INFINITY;
        }

        distTo[start.getId()] = 0;
        pq.add(start);

        while (!pq.isEmpty()) {
            Station v = pq.poll();
            if (v == end) {
                break;
            }
            for (Edge e : graph.getAdjacentEdges(v)) {
                Station w = e.getOther(v);
                if (distTo[v.getId()] + e.getWeight() < distTo[w.getId()]) {
                    distTo[w.getId()] = distTo[v.getId()] + e.getWeight();
                    edgeTo[w.getId()] = e;
                    if (pq.contains(w)) {
                        pq.remove(w);
                    }
                    pq.add(w);
                }
            }
        }
    }

    public Iterable<Edge> getPath() {
        List<Edge> path = new ArrayList<>();
        for (Edge e = edgeTo[graph.getVertexIndex(graph.getEndStation())]; e != null; e = edgeTo[graph.getVertexIndex(e.getOther(graph.getVertex(e)))]) {
            path.add(e);
        }
        Collections.reverse(path);
        return path;
    }
}

使用百度地图API查询路径

java
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public class BaiduMapPathFinder {
    private static final String AK = "your_ak";
    private static final String ROUTE_URL = "http://api.map.baidu.com/directionlite/v1/transit?origin=%s&destination=%s&ak=%s";
    private static final int TIMEOUT = 10000;

    public static String getRoute(String origin,