TileDownloadMapGenerator.java :  » Tools » mapsforge » org » mapsforge » android » maps » Android Open Source

/*
 * Copyright 2010, 2011 mapsforge.org
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.mapsforge.android.maps;

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.net.UnknownHostException;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;

/**
 * A MapGenerator that downloads map tiles from a server. To build an implementation for a
 * certain tile server, extend this class and implement the abstract methods.
 */
abstract class TileDownloadMapGenerator extends MapGenerator {
  private Bitmap decodedBitmap;
  private InputStream inputStream;
  private int[] pixelColors;
  private StringBuilder stringBuilder;
  private Bitmap tileBitmap;

  /**
   * Default constructor that must be called by subclasses.
   */
  TileDownloadMapGenerator() {
    this.stringBuilder = new StringBuilder(128);
  }

  @Override
  final void cleanup() {
    this.tileBitmap = null;
    if (this.decodedBitmap != null) {
      this.decodedBitmap.recycle();
      this.decodedBitmap = null;
    }
  }

  @Override
  final boolean executeJob(MapGeneratorJob mapGeneratorJob) {
    try {
      getTilePath(mapGeneratorJob.tile, this.stringBuilder);
      // read the data from the tile URL
      this.inputStream = new URL(this.stringBuilder.toString()).openStream();
      this.decodedBitmap = BitmapFactory.decodeStream(this.inputStream);
      this.inputStream.close();

      // check if the input stream could be decoded into a bitmap
      if (this.decodedBitmap == null) {
        return false;
      }

      // copy all pixels from the decoded bitmap to the color array
      this.decodedBitmap.getPixels(this.pixelColors, 0, Tile.TILE_SIZE, 0, 0,
          Tile.TILE_SIZE, Tile.TILE_SIZE);
      this.decodedBitmap.recycle();

      // copy all pixels from the color array to the tile bitmap
      if (this.tileBitmap != null) {
        this.tileBitmap.setPixels(this.pixelColors, 0, Tile.TILE_SIZE, 0, 0,
            Tile.TILE_SIZE, Tile.TILE_SIZE);
      }
      return true;
    } catch (UnknownHostException e) {
      Logger.d(e.getMessage());
      return false;
    } catch (IOException e) {
      Logger.e(e);
      return false;
    }
  }

  /**
   * Returns the host name of the tile download server.
   * 
   * @return the server name.
   */
  abstract String getServerHostName();

  /**
   * Stores the absolute path to the requested tile in the given StringBuilder.
   * 
   * @param tile
   *            the tile for which an image is required.
   * @param imagePath
   *            the StringBuilder to store the URL to the image.
   */
  abstract void getTilePath(Tile tile, StringBuilder imagePath);

  @Override
  final void prepareMapGeneration() {
    this.stringBuilder.setLength(0);
  }

  @Override
  final void setupMapGenerator(Bitmap bitmap) {
    this.tileBitmap = bitmap;
    this.pixelColors = new int[Tile.TILE_SIZE * Tile.TILE_SIZE];
  }
}