use a variable from one class in another class

Question

I am making an app in android and i am using google maps.

I have a navigation screen where users can put in a location.

then they click on a button and a mapview opens.

Here the location which they have entered should be navigated too.

When i run this code i get a nullpointerexception for plaats in my map.class

My Navigation code is:

   public class Navigatie extends Activity{
        public String plaats;   

        @Override
        public void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.navigatie);

            EditText text = (EditText)findViewById(R.id.title);
            this.plaats = text.getText().toString();

            // We create a new ImageButton which links to the map.java class 
            ImageButton imageButton = (ImageButton) findViewById(R.id.imageButton1);
            // We give a onclicklistener method to the button imageButton
                   imageButton.setOnClickListener(new OnClickListener() {

                // if the imageButton is clicked we start a new activity called "Map"
                public void onClick(View v) {
                    startActivity(new Intent(Navigatie.this, Map.class));
                }
            });
        }
    }

The code for my maps where the location display is coded, is: (just a part of the code)

 public Navigatie nav;

 @Override
 public void onCreate(Bundle savedInstanceState) {
 super.onCreate(savedInstanceState);
 setContentView(R.layout.map);

 mapView = (MapView) findViewById(R.id.mapview1);

 mc = mapView.getController();

 mapView.setBuiltInZoomControls(true);
 String plaats = nav.plaats;
 Geocoder geoCoder = new Geocoder(this, Locale.getDefault());
 try 
 {
   List<Address> addresses = geoCoder.getFromLocationName(plaats, 5);
   String strCompleteAddress = "";
   if (addresses.size() > 0) {
   GeoPoint p = new GeoPoint(
   (int) (addresses.get(0).getLatitude() * 1E6),
   (int) (addresses.get(0).getLongitude() * 1E6));
   mc.animateTo(p);
   mapView.invalidate();
   }
 } catch (IOException e) {
       e.printStackTrace();
 }

Answer 1

Add plaats to your intent, which starts the map using

intent.putExtra("location", this.plaats);

Then in you map activity, in oncreate:

String map_plaats = this.getIntent().getStringExtra("location");

Answer 2

You want to send string to other activity it seems.

For this you can use putExtra("key", "value"); and

you can get this string in Map.class like this

getIntent().getStringExtra("key");

Study here to know more about Intents