Android tips #1 - Make Google Navigator Intent

Se il vostro obiettivo è eseguire l'applicazione Google Navigator verso una destinazione precedentemente acquisita e memorizzata nelle SharedPreferences è sufficente incollare il codice seguente nella vostra applicazione:

1) Creare un oggetto LocationListener per agganciare la posizione:

private static final String C_PREFS_NAME = "gnav";

private static final int C_TWO_MINUTES = 1000 * 60 * 2;

private static final String C_LATITUDE = "latitude";

private static final String C_LONGITUDE = "longitude";

LocationListener mLocationListener = new LocationListener()

{   

public void onLocationChanged(Location location) {

if (isBetterLocation(location, currentBestLocation))

{

currentBestLocation = location;

SharedPreferences settings = getSharedPreferences(

C_PREFS_NAME, 0);  

SharedPreferences.Editor editor = settings.edit();     

editor.putString(

C_LATITUDE, Double.toString(currentBestLocation.getLatitude()));

editor.putString(

C_LONGITUDE, Double.toString(currentBestLocation.getLongitude()));

editor.commit();

}

}

protected boolean isBetterLocation(Location location, Location currentBestLocation)
{
if (currentBestLocation == null) {
return true;
}
  // Check whether the new location fix is newer or older
  long timeDelta = location.getTime() - currentBestLocation.getTime();
  boolean isSignificantlyNewer = timeDelta > C_TWO_MINUTES;
  boolean isSignificantlyOlder = timeDelta < -C_TWO_MINUTES;
  boolean isNewer = timeDelta > 0;
  // If it's been more than two minutes since the current location, use
  // the new location
  // because the user has likely moved
  if (isSignificantlyNewer) {
   return true;
   // If the new location is more than two minutes older, it must be
   // worse
  } else if (isSignificantlyOlder) {
   return false;
  }
  // Check whether the new location fix is more or less accurate
  int accuracyDelta = (int) (location.getAccuracy() - currentBestLocation
    .getAccuracy());
  boolean isLessAccurate = accuracyDelta > 0;
  boolean isMoreAccurate = accuracyDelta < 0;
  boolean isSignificantlyLessAccurate = accuracyDelta > 200;
  // Check if the old and new location are from the same provider
  boolean isFromSameProvider = isSameProvider(location.getProvider(),
    currentBestLocation.getProvider());
  // Determine location quality using a combination of timeliness and
  // accuracy
  if (isMoreAccurate) {
   return true;
  } else if (isNewer && !isLessAccurate) {
   return true;
  } else if (isNewer && !isSignificantlyLessAccurate
    && isFromSameProvider) {
   return true;
  }
  return false;
 }
 /** Checks whether two providers are the same */
private boolean isSameProvider(String provider1, String provider2) {
if (provider1 == null)
{
return provider2 == null;
}
return provider1.equals(provider2);
}
2) Recuperare la posizione precedentemente memorizzata e aprire Google Navigator.
...
SharedPreferences settings = getSharedPreferences(C_PREFS_NAME, 0);        
String uri = "google.navigation:q=" + settings.getString(C_LATITUDE,"") + "," + settings.getString(C_LONGITUDE, "");
Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse(uri));
startActivity(intent);
...