GoogleMapOverlayMapTileProvider.java

package it.fdev.unisaconnect.map;

import it.fdev.unisaconnect.FragmentMap;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

import android.content.res.AssetManager;

import com.google.android.gms.maps.model.Tile;
import com.google.android.gms.maps.model.TileProvider;

public class GoogleMapOverlayMapTileProvider implements TileProvider {

	private static final int TILE_WIDTH = 256;
	private static final int TILE_HEIGHT = 256;
	private static final int BUFFER_SIZE = 16 * 1024;

	private AssetManager assets;
	private String tilesFolder;

	public GoogleMapOverlayMapTileProvider(AssetManager assets, String tilesFolderName) {
		this.assets = assets;
		this.tilesFolder = tilesFolderName;
	}

	@Override
	public Tile getTile(int x, int y, int zoom) {

		/* conversion from TMS to XYZ tiles */
		y = (int) ((Math.pow(2, zoom)) - y - 1);

		if (!existsTile(x, y, zoom)) {
			return null;
		} else {
			byte[] image = readTileImage(x, y, zoom);
			return image == null ? null : new Tile(TILE_WIDTH, TILE_HEIGHT, image);
		}
	}

	private byte[] readTileImage(int x, int y, int zoom) {
		InputStream in = null;
		ByteArrayOutputStream buffer = null;

		try {
			in = assets.open(getTileFilename(x, y, zoom));
			buffer = new ByteArrayOutputStream();

			int nRead;
			byte[] data = new byte[BUFFER_SIZE];

			while ((nRead = in.read(data, 0, BUFFER_SIZE)) != -1) {
				buffer.write(data, 0, nRead);
			}
			buffer.flush();

			return buffer.toByteArray();
		} catch (IOException e) {
			e.printStackTrace();
			return null;
		} catch (OutOfMemoryError e) {
			e.printStackTrace();
			return null;
		} finally {
			if (in != null)
				try {
					in.close();
				} catch (Exception ignored) {
				}
			if (buffer != null)
				try {
					buffer.close();
				} catch (Exception ignored) {
				}
		}
	}

	private String getTileFilename(int x, int y, int zoom) {
		return tilesFolder + "/" + zoom + '/' + x + '/' + y + ".png";
	}

	private boolean existsTile(int x, int y, int zoom) {
		int minZoom = FragmentMap.MIN_ZOOM;
		int maxZoom = FragmentMap.MAX_ZOOM;

		if ((zoom < minZoom || zoom > maxZoom)) {
			return false;
		}

		return true;
	}
}