patrickyin

public TilePosition getTilePosition(float zoomLevel, double latitude, double longitude) {
  int tileZoom = round(zoomLevel);
  int tileX = (int) ((longitude + 180.0) / 360.0 * pow(2.0, tileZoom));
  int tileY = (int)((1.0 - log(tan(latitude * PI / 180.0) + 1.0 / cos(latitude * PI / 180.0)) / PI) / 2.0 * pow(2.0, tileZoom));
  tileY = (int) (pow(2.0, tileZoom) - tileY - 1.0); // flip Y, this is only for mbtiles file
  return new TilePosition(tileZoom, tileX, tileY);
}

patrickyin

public class TilePosition extends Object{
    private int zoom;
    private int x;
    private int y;
    public TilePosition(int zoom, int x, int y) {
        this.zoom = zoom;
        this.x = x;
        this.y = y;
    }
    public int getZoom() {

patrickyin

private byte[] getGridBLOBData(TilePosition tilePosition) {
    String[] columns = { "grid" };
    String[] args = { Integer.toString(tilePosition.getZoom()), Integer.toString(tilePosition.getX()), Integer.toString(tilePosition.getY()) };
    Cursor cursor = this.db.query("grids", columns, "zoom_level=? AND tile_column=? AND tile_row=?", args, null, null, null);
    if (cursor == null || cursor.getCount() == 0)
        return null;
    cursor.moveToFirst();
    byte[] data = cursor.getBlob(0);
    cursor.close();
    return data;

patrickyin

private byte[] decompress(byte[] compressedData)
{
    if(compressedData == null) return null;
    Inflater inflater = new Inflater();
    inflater.setInput(compressedData);
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream(compressedData.length);
    byte[] buffer = new byte[1024];
    while (!inflater.finished()) {
        int count = 0;
        try {