Manejo del caso cuando se ha perdido un giro en Google Maps

Estoy trabajando en una aplicación de navegación Android para personas ciegas. Así que, naturalmente, no uso de mostrar mapa en la pantalla. Mi código por ahora obtiene la ruta mediante la construcción de una url y luego analizar el documento html. Quiero hacer esto vivo, es decir, quiero manejar el caso cuando él / ella se va de la ruta o va en la dirección equivocada, quiero que mi aplicación para alertarlo.

¿Es posible utilizar una función de Google Maps? Si es posible, proporcione detalles sobre esa característica o si no existe tal característica, entonces es posible utilizar la función existente y utilizarla de alguna manera para ayudar a resolver el problema.

Este es mi código actual:

public class GPSTracking extends Activity implements TextToSpeech.OnInitListener { protected static final int RESULT_SPEECH_start = 1; protected static final int RESULT_SPEECH_end = 2; protected static final int RESTART_ALL = 3; //total distance travelled till last turn Float totalDistance; //distance to be travelled from present point to the next point Float obtainedDistance; //upper button Button btnShowLocation; //bottom button Button btnShowLocationNo; //to narate what user should do. TextToSpeech tts; //used to get name of current location Geocoder geocoder; //used to find positioning feature GPS gps; //start and position of the journey String startPosition=null, endPosition=null; //strings containing the path. String[] string = null; //vibrate the mobile Vibrator viberator; //indexing the present value of string which contains the path int i = 0; //to maintain proper order of events int steps=0; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); //button on top btnShowLocation = (Button) findViewById(R.id.trueButton); //button on the lower side btnShowLocationNo = (Button) findViewById(R.id.falseButton); //initialising the text to speech tts = new TextToSpeech(this, this); //initialising the vibrator. viberator = (Vibrator) getSystemService(Context.VIBRATOR_SERVICE); //to know what the current location btnShowLocation.setOnClickListener(new View.OnClickListener() { //to avoid start of multiple threads boolean mytaskStarted=false; String str=null; @Override public void onClick(View v) { if(steps==0){ //to make sure values are reset totalDistance=(float)0; obtainedDistance=(float)0; mytaskStarted=false; string=null; str=null; i=0; //only ask for initial position if not set if(startPosition == null){ speakOut("Please enter the start position"); //takes the input using speech to text intentGenerator(RESULT_SPEECH_start); } else{ //to enter the destination speakOut("press the button again"); steps=1; } } else if(steps==1){ //to enter the destination speakOut("Please enter the destination"); intentGenerator(RESULT_SPEECH_end); } else if(steps==2){ //for a impatient user speakOut("please wait"); //to avoid start of many asynchronous task if(!mytaskStarted){ mytaskStarted=true; //asynchronous task to find the path to be followed new GetPath().execute(); } } else if(steps==3){ if (string != null && i < string.length) { if(gps!=null && gps.isGpsEnabled()){ speakOut(i + 1 + " " + string[i]); if(i>0 && i<string.length-1 && (string[i]+" ").lastIndexOf(" m ")>-1){ str=(string[i]+" ").substring(0,(string[i]+" ").lastIndexOf(" m ")+3); obtainedDistance=Float.parseFloat(str.substring(1+str.substring(0,str.substring(0,str.lastIndexOf(" ")).lastIndexOf(" ")).lastIndexOf(" "),str.substring(0,str.lastIndexOf(" ")).lastIndexOf(" "))); //increment only when present distance greater than distance in present string so that one will know when to turn. if(((totalDistance+obtainedDistance)-gps.getApprximateDistance())<10) { i++; totalDistance=totalDistance+obtainedDistance; } } else if(i>0 && i<string.length-1 && (string[i]+" ").lastIndexOf(" km ")>-1){ str=(string[i]+" ").substring(0,(string[i]+" ").lastIndexOf(" km ")+4); obtainedDistance=Float.parseFloat(str.substring(1+str.substring(0,str.substring(0,str.lastIndexOf(" ")).lastIndexOf(" ")).lastIndexOf(" "),str.substring(0,str.lastIndexOf(" ")).lastIndexOf(" "))); obtainedDistance*=1000; //increment only when present distance greater than distance in present string so that one will know when to turn. if(((totalDistance+obtainedDistance)-gps.getApprximateDistance())<10) { i++; totalDistance=totalDistance+obtainedDistance; } } else if(i==0 ){ i++; } } else if(gps!=null){ gps.resetDistance(); gps.stopUsingGPS(); //if gps not working. speakOut(i + 1 + " " + string[i]); i++; } else{ speakOut(i + 1 + " " + string[i]); i++; } } else if (string != null && i >= string.length) { i = 0; } } } }); //to get present location btnShowLocation.setOnLongClickListener(new View.OnLongClickListener() { @Override public boolean onLongClick(View v) { if(gps==null){ gps = new GPS(AndroidGPSTrackingActivity.this); } if (gps.canGetLocation()) { double longitude = gps.getLongitude(); double latitude = gps.getLatitude(); Geocoder geocoder = new Geocoder(getApplicationContext(), Locale.getDefault()); try { //obtain the address of present location List<Address> listAddresses = geocoder.getFromLocation(latitude, longitude, 1); if(null!=listAddresses&&listAddresses.size()>0){ if (listAddresses.size() > 0) { StringBuilder result = new StringBuilder(); for(int i = 0; i < listAddresses.size(); i++){ Address address = listAddresses.get(i); int maxIndex = address.getMaxAddressLineIndex(); for (int x = 0; x <= maxIndex; x++ ){ if(address.getAddressLine(x)!=null){ result.append(address.getAddressLine(x)); result.append(","); } } if(address.getLocality()!=null){ result.append(address.getLocality()); result.append("\n\n"); } } //if position accurate if(gps.isGpsEnabled()){ speakOut(result.toString()+" is Your current location"); startPosition=result.toString(); Toast.makeText( getApplicationContext(),startPosition, Toast.LENGTH_LONG).show(); } else if(gps.isNetworkEnabled()){ speakOut(result.toString()+" is Your current approximate location. You have to give input of your present location on your own."); Toast.makeText( getApplicationContext(),result.toString(), Toast.LENGTH_LONG).show(); } } } } catch (IOException e) { e.printStackTrace(); } } else { gps.showSettingsAlert(); startPosition=null; speakOut(" please turn on gps"); } return false; } }); //to know what the previous direction string btnShowLocationNo.setOnClickListener(new View.OnClickListener() { int j=0; @Override public void onClick(View arg0) { if(string!=null && j<string.length){ speakOut(j + 1 + " " + string[j]); j++; } else if(string!=null && j>=string.length){ j=0; } } }); //to reset all values for fresh start btnShowLocationNo.setOnLongClickListener(new View.OnLongClickListener() { @Override public boolean onLongClick(View v) { // TODO Auto-generated method stub speakOut("Values reset"); steps=0; string=null; i=0; startPosition=null; gps.stopUsingGPS(); gps=null; endPosition=null; return false; } }); } //function to handle he text obtained from speech to text. @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { super.onActivityResult(requestCode, resultCode, data); switch (requestCode) { //set the start case RESULT_SPEECH_start: if (resultCode == RESULT_OK && null != data) { ArrayList<String> text = data .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS); Toast.makeText(getApplicationContext(), text.get(0), Toast.LENGTH_SHORT).show(); startPosition = text.get(0); steps=1; //speakOut("please press button again"); } else{ steps=0; } break; //to set the end case RESULT_SPEECH_end: if (resultCode == RESULT_OK && null != data) { ArrayList<String> text = data .getStringArrayListExtra(RecognizerIntent.EXTRA_RESULTS); Toast.makeText(getApplicationContext(), text.get(0), Toast.LENGTH_SHORT).show(); endPosition = text.get(0); steps=2; } else{ steps=1; } break; } } //function to generate intent to take speech input public void intentGenerator(int code) { Intent intent = new Intent(RecognizerIntent.ACTION_RECOGNIZE_SPEECH); intent.putExtra(RecognizerIntent.EXTRA_LANGUAGE_MODEL, "en-US"); try { startActivityForResult(intent, code); } catch (ActivityNotFoundException a) { Toast.makeText(getApplicationContext(), "Opps! Your device doesn't support Speech to Text", Toast.LENGTH_SHORT).show(); speakOut("Opps! Your device doesn't support Speech to Text"); } } //mobile gives instruction. private void speakOut(String text) { tts.speak(text, TextToSpeech.QUEUE_FLUSH, null); while (tts.isSpeaking()) { try { Thread.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } //asynchronous task to get the path. THIS IS USED TO AVOID OVERLOAD THE MAIN THRED AND AVOID FORCE CLOSE OF THE APPLICATION private class GetPath extends AsyncTask<Void, Void, Void> { @Override protected Void doInBackground(Void... params) { try { string=null; String html=""; //forming url URL net = new URL(("http://maps.google.com/maps?saddr="+startPosition+" &daddr= "+endPosition).replaceAll(" ","%20")); URLConnection netConnection = null; netConnection = net.openConnection(); //to take the input from google maps BufferedReader in = null; in = new BufferedReader(new InputStreamReader(netConnection.getInputStream())); String inputLine; while ((inputLine = in.readLine()) != null) { html+=inputLine; } //jsoup parser to parse the document obtained from google maps Document doc = Jsoup.parse(html); //obtain necessary part of the document Elements el = doc.getElementsByClass("dir-mrgnr"); //to remove html tags String str = el.text(); str = str.replaceAll("[0-9]+[.] ", "\n"); string = str.split("\n"); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } return null; } @Override protected void onProgressUpdate(Void... values) { // TODO Auto-generated method stub super.onProgressUpdate(values); } @Override protected void onPostExecute(Void result) { // TODO Auto-generated method stub super.onPostExecute(result); //so that on press of button again mobile can read the directions to users steps=3; } } @Override public void onDestroy() { //shutdown if (tts != null) { tts.stop(); tts.shutdown(); } super.onDestroy(); } @Override protected void onStart() { gps = new GPS(AndroidGPSTrackingActivity.this); super.onStart(); } @Override protected void onStop() { if (tts != null) { tts.stop(); tts.shutdown(); } if(gps!=null){ gps.stopUsingGPS(); } super.onStop(); } @Override public void onInit(int status) { //initialising the text to speech if (status == TextToSpeech.SUCCESS) { int result = tts.setLanguage(Locale.US); if (result == TextToSpeech.LANG_MISSING_DATA || result == TextToSpeech.LANG_NOT_SUPPORTED) { Log.e("TTS", "Language is not supported"); } else { btnShowLocation.setEnabled(true); } } else { Log.e("TTS", "Initilization Failed"); } } }