使用 Google maps api 在 Android 上获取 Marker 的位置

Question

我无法获取我放置在地图上的标记的位置。将标记放在地图上后，我按下按钮显示 Toast，显示标记的纬度和经度，但应用程序正在强制关闭。

这是我的方法

 public void markerLoc(View view)
    {
        LatLng lat = marker.getPosition();
        double lat1 = lat.latitude;
        double lng1 = lat.longitude;
        Toast.makeText(getBaseContext(),"lat: "+lat1+" & long: "+lng1,Toast.LENGTH_SHORT).show();
    }

Basically i want to add a marker to the map and on pressing the button the marker's location is to be shown. If the marker is moved the new location is to be shown on pressing the button.

Thanks in advance :)

my activity

public class Locate extends FragmentActivity implements LocationListener {

    GoogleMap googleMap;
    double latitude,longitude;
    static int i=1;
    GPSTracker gps;
    Marker marker;
    LatLng lat;
    //Location location;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.locate);
        int status = GooglePlayServicesUtil.isGooglePlayServicesAvailable(getBaseContext());


        if(status!= ConnectionResult.SUCCESS){

            int requestCode = 10;
            Dialog dialog = GooglePlayServicesUtil.getErrorDialog(status, this, requestCode);
            dialog.show();

        }else {


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


            googleMap = fm.getMap();


            googleMap.setMyLocationEnabled(true);


            LocationManager locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);


            Criteria criteria = new Criteria();


            String provider = locationManager.getBestProvider(criteria, true);


            Location location = locationManager.getLastKnownLocation(provider);

            if(location!=null){
                onLocationChanged(location);
            }
            locationManager.requestLocationUpdates(provider, 20000, 0, this);
        }


    }



    @Override
    public void onLocationChanged(Location location) {

        TextView tvLocation = (TextView) findViewById(R.id.tv_location);
        Toast.makeText(getBaseContext(),"lat: "+location.getLatitude()+"long: "+location.getLatitude(),Toast.LENGTH_LONG).show();

       latitude = location.getLatitude();

        longitude = location.getLongitude();


        LatLng latLng = new LatLng(latitude, longitude);


        googleMap.moveCamera(CameraUpdateFactory.newLatLng(latLng));


        googleMap.animateCamera(CameraUpdateFactory.zoomTo(15));


        tvLocation.setText("Latitude:" +  latitude  + ", Longitude:"+ longitude );



    }


    @Override
    public void onProviderDisabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onProviderEnabled(String provider) {
        // TODO Auto-generated method stub
    }

    @Override
    public void onStatusChanged(String provider, int status, Bundle extras) {
        // TODO Auto-generated method stub
    }
    public void Dest(View view){
        if(i==1) {
            i=0;
            gps = new GPSTracker(Locate.this);


            if(gps.canGetLocation()){

                double latitude = gps.getLatitude();
                double longitude = gps.getLongitude();


                Toast.makeText(getApplicationContext(), "Your Location is - \nLat: " + latitude + "\nLong: " + longitude, Toast.LENGTH_LONG).show();
               marker = googleMap.addMarker(new MarkerOptions()
                        .position(new LatLng(latitude+0.0005, longitude+0.0005))
                        .title("Your destination")
                        .draggable(true));
            }else{

                gps.showSettingsAlert();
            }

        }
        else
            Toast.makeText(getBaseContext(),"You can add only one destination spot",Toast.LENGTH_SHORT).show();
    }

    public void Clear(View view)
    {
        i=1;
        googleMap.clear();
    }

    public void markerLoc(View view) {

        if (marker != null) {
            lat = marker.getPosition();
            double lat1 = lat.latitude;
            double lng1 = lat.longitude;
            if(getBaseContext() != null) {
                Toast.makeText(getBaseContext(), "lat: " + lat1 + " & long: " + lng1, Toast.LENGTH_SHORT).show();
            }
        }
    }

} 我的xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Location activity"
        android:id="@+id/tv_location"
        android:layout_gravity="center_horizontal" />
    <fragment xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/map"
        android:layout_width="match_parent"
        android:layout_height="500dp"
        class="com.google.android.gms.maps.SupportMapFragment" />

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent">


        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Add destination"
            android:onClick="Dest"
            android:id="@+id/dest" />

        <Button
            style="?android:attr/buttonStyleSmall"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Clear"
            android:id="@+id/clear"
            android:onClick="Clear"
            android:layout_alignParentTop="true"
            android:layout_alignParentRight="true"
            android:layout_alignParentEnd="true" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="MarkerLoc"
            android:id="@+id/button"
            android:onClick="markerLoc"
            android:layout_alignParentBottom="true"
            android:layout_centerHorizontal="true" />

    </RelativeLayout>



</LinearLayout>

Dest 按钮会添加一个新标记，该标记距离当前位置稍远。如果我将标记移动到新位置，然后按 markerLoc 按钮，位置似乎没有改变，它总是显示第一个位置。

Answer 1

public void markerLoc(View view)
{
    if(marker != null)
    {
        LatLng lat = marker.getPosition();
        double lat1 = lat.latitude;
        double lng1 = lat.longitude;
        if(getBaseContext() != null)
        {
            Toast.makeText(getBaseContext(),"lat: "+lat1+" & long:     "+lng1,Toast.LENGTH_SHORT).show();
        }
    }
}