android - How to move a map under a marker?

Question

Suppose that we have a centered marker on the map, when we move the map with our fingers we can see that marker would no longer displayed when you got out of bounds of the area. So how can we make a marker that would remain always on the center of the map although we move the map anywhere? There is an app named UBER and they provide this feature, you don't drag and drop the marker you just move the map and the marker remained it's position.

Here is a screenshot:

As you can see green marker is on the center of screen when we move the map it remained its place but shows the new position when the user stop moving the map. How can we do like this?

I have a code that shows the address when you drag&drop the marker, how about displaying the address again but this time not by dragging, moving the map? Hope you can understand any ideas would be great.

public class MainActivity extends AbstractMapActivity implements
    OnNavigationListener, OnInfoWindowClickListener,
    OnMarkerDragListener {
  private static final String STATE_NAV="nav";
  private static final int[] MAP_TYPE_NAMES= { R.string.normal,
    R.string.hybrid, R.string.satellite, R.string.terrain };
  private static final int[] MAP_TYPES= { GoogleMap.MAP_TYPE_NORMAL,
    GoogleMap.MAP_TYPE_HYBRID, GoogleMap.MAP_TYPE_SATELLITE,
    GoogleMap.MAP_TYPE_TERRAIN };
private GoogleMap map=null;
String filterAddress = "";
Marker marker;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    if (readyToGo()) {
        setContentView(R.layout.activity_main);

        SupportMapFragment mapFrag=
            (SupportMapFragment)getSupportFragmentManager().findFragmentById(R.id.map);

        mapFrag.setRetainInstance(true);
        initListNav();

        map=mapFrag.getMap();

        if (savedInstanceState == null) {
            CameraUpdate center=
                CameraUpdateFactory.newLatLng(new LatLng(
                        41.003739,
                        28.999572));
            CameraUpdate zoom=CameraUpdateFactory.zoomTo(10);

            map.moveCamera(center);
            map.animateCamera(zoom);

            addMarker(map, 41.003739, 28.999572, R.string.un, R.string.united_nations);

              map.setInfoWindowAdapter(new PopupAdapter(getLayoutInflater()));
              map.setOnInfoWindowClickListener(this);
              map.setOnMarkerDragListener(this);
        }
    }
}

@Override
public boolean onNavigationItemSelected(int itemPosition, long itemId) {
    map.setMapType(MAP_TYPES[itemPosition]);

    return(true);
}

@Override
public void onSaveInstanceState(Bundle savedInstanceState) {
    super.onSaveInstanceState(savedInstanceState);

    savedInstanceState.putInt(STATE_NAV,
            getSupportActionBar().getSelectedNavigationIndex());
}

@Override
public void onRestoreInstanceState(Bundle savedInstanceState) {
    super.onRestoreInstanceState(savedInstanceState);
getSupportActionBar().setSelectedNavigationItem(savedInstanceState.getInt(STATE_NAV));
}

@Override
public void onInfoWindowClick(Marker marker) {
    Toast.makeText(this, marker.getTitle(), Toast.LENGTH_LONG).show();
}

@Override
public void onMarkerDragStart(Marker marker) {
    LatLng position=marker.getPosition();

    Log.d(getClass().getSimpleName(), String.format("Drag from %f:%f",
            position.latitude,
            position.longitude));
}

@Override
public void onMarkerDrag(Marker marker) {
    LatLng position=marker.getPosition();

    Log.d(getClass().getSimpleName(),
            String.format("Dragging to %f:%f", position.latitude,
                    position.longitude));
}

@Override
public void onMarkerDragEnd(Marker marker) {
    LatLng position=marker.getPosition();

    String filterAddress = "";
    Geocoder geoCoder = new Geocoder(
            getBaseContext(), Locale.getDefault());
    try {
        List<Address> addresses = geoCoder.getFromLocation(
                position.latitude, 
                position.longitude, 1);

        if (addresses.size() > 0) {
            for (int index = 0; 
            index < addresses.get(0).getMaxAddressLineIndex(); index++)
                filterAddress += addresses.get(0).getAddressLine(index) + " ";
        }
    }catch (IOException ex) {        
        ex.printStackTrace();
    }catch (Exception e2) {
        // TODO: handle exception
        e2.printStackTrace();
    } 
    Log.d(getClass().getSimpleName(),
            String.format("Dragging to %f:%f", position.latitude,
                    position.longitude));
    TextView myTextView = (TextView) findViewById(R.id.test);

    myTextView.setText("Address is: " + filterAddress);

}

private void initListNav() {
    ArrayList<String> items=new ArrayList<String>();
    ArrayAdapter<String> nav=null;
    ActionBar bar=getSupportActionBar();

    for (int type : MAP_TYPE_NAMES) {
        items.add(getString(type));
    }

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH) {
        nav=
            new ArrayAdapter<String>(
                    bar.getThemedContext(),
                    android.R.layout.simple_spinner_item,
                    items);
    }
    else {
        nav=
            new ArrayAdapter<String>(
                    this,
                    android.R.layout.simple_spinner_item,
                    items);
    }

    nav.setDropDownViewResource(android.R.layout.simple_spinner_dropdown_item);
    bar.setNavigationMode(ActionBar.NAVIGATION_MODE_LIST);
    bar.setListNavigationCallbacks(nav, this);
}

private void addMarker(GoogleMap map, double lat, double lon,
        int title, int snippet)

{
    map.addMarker(new MarkerOptions().position(new LatLng(lat, lon))
            .icon(BitmapDescriptorFactory.fromResource(R.drawable.pin))

            .draggable(true));
}
    }

Here is the xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/layout1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:layout_below="@+id/img_header" >

<fragment
    android:id="@+id/map"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    class="com.google.android.gms.maps.SupportMapFragment" />

<TextView
    android:id="@+id/test"
    android:layout_width="match_parent"
    android:layout_height="90dp"
    android:layout_alignParentRight="true"
    android:text="Address : "
    android:textColor="#FF0000"
    android:textSize="22sp" />
</RelativeLayout>

Answer 1

Two easy steps:

Step 1

I used a RelativeLayout as parent of fragment with map and center in it an ImageView (which will do as the centered map marker just like in uber or easy taxi apps):

<!-- Map and ImageView in center for simulating the map marker -->
<RelativeLayout
    android:id="@+id/confirm_address_map_wrapper"
    android:layout_width="match_parent"
    android:layout_height="220dp">

    <fragment
        android:id="@+id/confirm_address_map_fragment"
        android:name="com.google.android.gms.maps.MapFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_centerInParent="true"
        />
    <!-- Image View that acts as map marker notice centerInParent-->

     <View
        android:id="@+id/view"
        android:layout_width="1dp"
        android:layout_height="1dp"
        android:layout_centerInParent="true"/>


    <ImageView
        android:id="@+id/confirm_address_map_custom_marker"
        android:layout_width="@dimen/ICON_DEFAULT_SIZE"
        android:layout_height="@dimen/ICON_DEFAULT_SIZE"
        android:layout_above="@+id/view"
        android:layout_centerHorizontal="true"
        android:src="@mipmap/my_map_marker"/>
</RelativeLayout>

Step 2

onMapReady() method at my activity I use googleMap instance method setOnCameraChangeListener() that lets me listen when the map is used and get latitude and longitude based on the center of camera position:

    @Override
    public void onMapReady(GoogleMap googleMap) {

        googleMap.setOnCameraChangeListener(new GoogleMap.OnCameraChangeListener() {
        @Override
        public void onCameraChange(CameraPosition cameraPosition) {

           Log.i("centerLat",cameraPosition.target.latitude);

           Log.i("centerLong",cameraPosition.target.longitude);
        }
    });

}

UPDATE:
OnCameraChangeListener is deprecated . Please use OnCameraIdleListener:
[Source: https://stackoverflow.com/a/38732283/421467]