WeatherFragment.java

/***
  Copyright (c) 2012-2014 CommonsWare, LLC
  Licensed under the Apache License, Version 2.0 (the "License"); you may not
  use this file except in compliance with the License. You may obtain a copy
  of the License at http://www.apache.org/licenses/LICENSE-2.0. Unless required
  by applicable law or agreed to in writing, software distributed under the
  License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS
  OF ANY KIND, either express or implied. See the License for the specific
  language governing permissions and limitations under the License.
  
  Covered in detail in the book _The Busy Coder's Guide to Android Development_
    https://commonsware.com/Android
 */

package com.commonsware.android.weather;

import android.content.Context;
import android.location.Location;
import android.location.LocationListener;
import android.location.LocationManager;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.webkit.WebViewFragment;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.StringReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.util.ArrayList;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;

public class WeatherFragment extends WebViewFragment implements
    LocationListener {
  private String template=null;
  private LocationManager mgr=null;

  @Override
  public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setRetainInstance(true);

    template=getActivity().getString(R.string.url);
    mgr=
        (LocationManager)getActivity().getSystemService(Context.LOCATION_SERVICE);
  }

  @Override
  public void onStart() {
    super.onStart();

    mgr.requestLocationUpdates(LocationManager.GPS_PROVIDER, 3600000,
                               1000, this);
  }

  @Override
  public void onStop() {
    super.onStop();

    mgr.removeUpdates(this);
  }

  @Override
  public void onLocationChanged(Location location) {
    FetchForecastTask task=new FetchForecastTask();

    task.execute(location);
  }

  @Override
  public void onProviderDisabled(String provider) {
    // required for interface, not used
  }

  @Override
  public void onProviderEnabled(String provider) {
    // required for interface, not used
  }

  @Override
  public void onStatusChanged(String provider, int status, Bundle extras) {
    // required for interface, not used
  }

  private String getForecastXML(String path) throws IOException {
    BufferedReader reader=null;
    URL url=new URL(path);
    HttpURLConnection c=(HttpURLConnection)url.openConnection();
    
    try {
      reader=
          new BufferedReader(new InputStreamReader(c.getInputStream()));

      StringBuilder buf=new StringBuilder();
      String line=null;

      while ((line=reader.readLine()) != null) {
        buf.append(line + "\n");
      }

      return(buf.toString());
    }
    finally {
      if (reader != null) {
        reader.close();
      }
      
      c.disconnect();
    }
  }

  private ArrayList<Forecast> buildForecasts(String raw)
                                                        throws Exception {
    ArrayList<Forecast> forecasts=new ArrayList<Forecast>();
    DocumentBuilder builder=
        DocumentBuilderFactory.newInstance().newDocumentBuilder();
    Document doc=builder.parse(new InputSource(new StringReader(raw)));
    NodeList times=doc.getElementsByTagName("start-valid-time");

    for (int i=0; i < times.getLength(); i++) {
      Element time=(Element)times.item(i);
      Forecast forecast=new Forecast();

      forecasts.add(forecast);
      forecast.setTime(time.getFirstChild().getNodeValue());
    }

    NodeList temps=doc.getElementsByTagName("value");

    for (int i=0; i < temps.getLength(); i++) {
      Element temp=(Element)temps.item(i);
      Forecast forecast=forecasts.get(i);

      forecast.setTemp(Integer.valueOf(temp.getFirstChild().getNodeValue()));
    }

    NodeList icons=doc.getElementsByTagName("icon-link");

    for (int i=0; i < icons.getLength(); i++) {
      Element icon=(Element)icons.item(i);
      Forecast forecast=forecasts.get(i);

      forecast.setIcon(icon.getFirstChild().getNodeValue());
    }

    return(forecasts);
  }

  String generatePage(ArrayList<Forecast> forecasts) {
    StringBuilder bufResult=new StringBuilder("<html><body><table>");

    bufResult.append("<tr><th width=\"50%\">Time</th>"
        + "<th>Temperature</th><th>Forecast</th></tr>");

    for (Forecast forecast : forecasts) {
      bufResult.append("<tr><td align=\"center\">");
      bufResult.append(forecast.getTime());
      bufResult.append("</td><td align=\"center\">");
      bufResult.append(forecast.getTemp());
      bufResult.append("</td><td><img src=\"");
      bufResult.append(forecast.getIcon());
      bufResult.append("\"></td></tr>");
    }

    bufResult.append("</table></body></html>");

    return(bufResult.toString());
  }

  class FetchForecastTask extends AsyncTask<Location, Void, String> {
    Exception e=null;

    @Override
    protected String doInBackground(Location... locs) {
      String page=null;

      try {
        Location loc=locs[0];
        String url=
            String.format(template, loc.getLatitude(),
                          loc.getLongitude());

        page=generatePage(buildForecasts(getForecastXML(url)));
      }
      catch (Exception e) {
        this.e=e;
      }

      return(page);
    }

    @Override
    protected void onPostExecute(String page) {
      if (e == null) {
        getWebView().loadDataWithBaseURL(null, page, "text/html",
                                         "UTF-8", null);
      }
      else {
        Log.e(getClass().getSimpleName(), "Exception fetching data", e);
        Toast.makeText(getActivity(),
                       String.format(getString(R.string.error),
                                     e.toString()), Toast.LENGTH_LONG)
             .show();
      }
    }
  }
}