Java tutorial
/* * Copyright 2014 Thomas Hoffmann * * 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. */ package de.j4velin.mapsmeasure; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileWriter; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.util.HashMap; import java.util.LinkedList; import java.util.List; import java.util.Stack; import org.apache.http.HttpEntity; import org.apache.http.HttpResponse; import org.apache.http.client.HttpClient; import org.apache.http.client.methods.HttpGet; import org.apache.http.impl.client.DefaultHttpClient; import org.apache.http.protocol.BasicHttpContext; import org.apache.http.protocol.HttpContext; import com.google.android.gms.maps.model.LatLng; import android.content.Context; import android.net.ConnectivityManager; import android.net.Uri; import android.util.Pair; import android.util.TypedValue; public class Util { private static HashMap<LatLng, Float> elevationCache; // from // http://mrtn.me/blog/2012/03/17/get-the-height-of-the-status-bar-in-android/ static int getStatusBarHeight(final Context c) { int result = 0; int resourceId = c.getResources().getIdentifier("status_bar_height", "dimen", "android"); if (resourceId > 0) { result = c.getResources().getDimensionPixelSize(resourceId); } return result; } static int dpToPx(final Context c, int dp) { return (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, c.getResources().getDisplayMetrics()); } /** * Writes the given trace of points to the given file in CSV format, * separated by ";" * * @param f * the file to write to * @param trace * the trace to write * @throws IOException */ static void saveToFile(final File f, final Stack<LatLng> trace) throws IOException { if (!f.exists()) f.createNewFile(); BufferedWriter out = new BufferedWriter(new FileWriter(f)); LatLng current; for (int i = 0; i < trace.size(); i++) { current = trace.get(i); out.append(current.latitude + ";" + current.longitude + "\n"); } out.close(); } /** * Replaces the current points on the map with the one from the provided * file * * @param f * the file to read from * @param m * the Map activity to add the new points to * @throws IOException */ static void loadFromFile(final Uri f, final Map m) throws IOException { List<LatLng> list = new LinkedList<LatLng>(); BufferedReader in = new BufferedReader(new InputStreamReader(m.getContentResolver().openInputStream(f))); String line; String[] data; while ((line = in.readLine()) != null) { data = line.split(";"); try { list.add(new LatLng(Double.parseDouble(data[0]), Double.parseDouble(data[1]))); } catch (NumberFormatException nfe) { // should not happen when opening a valid file nfe.printStackTrace(); } catch (ArrayIndexOutOfBoundsException aiabe) { // should not happen when opening a valid file aiabe.printStackTrace(); } } in.close(); m.clear(); for (int i = 0; i < list.size(); i++) { m.addPoint(list.get(i)); } } /** * Get the altitude data for a specific point * * @param p * the point to get the altitude for * @param httpClient * can be null if no network query should be performed * @param localContext * can be null if no network query should be performed * @return the altitude at point p or -Float.MAX_VALUE if no valid data * could be fetched * @throws IOException */ static float getAltitude(final LatLng p, final HttpClient httpClient, final HttpContext localContext) throws IOException { if (elevationCache == null) { elevationCache = new HashMap<LatLng, Float>(30); } if (elevationCache.containsKey(p)) { return elevationCache.get(p); } else if (httpClient != null && localContext != null) { float altitude = -Float.MAX_VALUE; String url = "http://maps.googleapis.com/maps/api/elevation/xml?locations=" + String.valueOf(p.latitude) + "," + String.valueOf(p.longitude) + "&sensor=true"; HttpGet httpGet = new HttpGet(url); HttpResponse response = httpClient.execute(httpGet, localContext); HttpEntity entity = response.getEntity(); if (entity != null) { InputStream instream = entity.getContent(); int r = -1; StringBuffer respStr = new StringBuffer(); while ((r = instream.read()) != -1) respStr.append((char) r); String tagOpen = "<elevation>"; String tagClose = "</elevation>"; if (respStr.indexOf(tagOpen) != -1) { int start = respStr.indexOf(tagOpen) + tagOpen.length(); int end = respStr.indexOf(tagClose); altitude = Float.parseFloat(respStr.substring(start, end)); elevationCache.put(p, altitude); } instream.close(); } return altitude; } else { return elevationCache.get(p); } } /** * Calculates the up- & downwards elevation along the passed trace. * * This method might need to connect to the Google Elevation API and * therefore must not be called from the main UI thread. * * @param trace * @return null if an error occurs, a pair of two float values otherwise: * first one is the upwards elevation, second one downwards * * based on * http://stackoverflow.com/questions/1995998/android-get-altitude * -by-longitude-and-latitude */ static Pair<Float, Float> getElevation(final List<LatLng> trace) { float up = 0, down = 0; float lastElevation = -Float.MAX_VALUE, currentElevation; HttpClient httpClient = new DefaultHttpClient(); HttpContext localContext = new BasicHttpContext(); float difference; try { for (LatLng p : trace) { currentElevation = getAltitude(p, httpClient, localContext); // current and last point have a valid elevation data -> // calculate difference if (currentElevation > -Float.MAX_VALUE && lastElevation > -Float.MAX_VALUE) { difference = currentElevation - lastElevation; if (difference > 0) up += difference; else down += difference; } lastElevation = currentElevation; } } catch (Exception e) { e.printStackTrace(); return null; } return new Pair<Float, Float>(up, down); } /** * Tests for an internet connection. * * @param context * @return true, if connected to the internet */ static boolean checkInternetConnection(final Context context) { final ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE); // test for connection return cm.getActiveNetworkInfo() != null && cm.getActiveNetworkInfo().isAvailable() && cm.getActiveNetworkInfo().isConnected(); } }