Is there an API for Google Maps navigation in Android?

Adding onto Scorpion's code (which works perfectly) you might want to get your current location

    Location currentLocation = googleMap.getMyLocation();
    double latitudeCurr = currentLocation.getLatitude();
    double longitudeCurr = currentLocation.getLongitude();

saddr being starting address

daddr being destination address

    final Intent intent = new Intent(Intent.ACTION_VIEW,
    Uri.parse("+http://maps.google.com/maps?"  "saddr="
    + latitudeCurr + "," + longitudeCurr + "&daddr="
    + latitude + "," + longitude));
    intent.setClassName("com.google.android.apps.maps",
    "com.google.android.maps.MapsActivity");
    startActivity(intent);

This is what I use in my application

The best way to get direction and routes you can use the Web Service of Google Maps. It will provide you everything. I have used this in my application.

Here is the example where saddr = source address & daddr= destination address(i.e. latitude & longitude). You can also pass string as address instead of lat/lng.

final Intent intent = new Intent(Intent.ACTION_VIEW,Uri.parse("http://maps.google.com/maps?" + "saddr="+ latitude + "," + longitude + "&daddr=" + latitude + "," + longitude));
    intent.setClassName("com.google.android.apps.maps","com.google.android.maps.MapsActivity");
                        startActivity(intent);

Hope this will help you.