GoogleMap give me null when trying to draw on the map outside

Question

How can protect GoogleMap properly from being null?

It currently says mMap null inside the drawOnMap() method, but works when adding it to the onMapReady() method.

I wonder because isn't it true that the map may be initiated before I get the values from my intent if I ask for drawOnMap() inside onMapReady()?

mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(startLatLng, 10));

public class DetailActivity extends AppCompatActivity implements OnMapReadyCallback {

private GoogleMap mMap;
private String locationA;
private String locationB;
private ArrayList<LatLng> latLngList;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_detail);

    // Check if Google Maps have been activated, else starting it again.
    if (mMap == null) {
        SupportMapFragment smf = (SupportMapFragment) this.getSupportFragmentManager().findFragmentById(R.id.map);
        smf.getMapAsync(this);
    }

    // Settings up the views
    TextView mDistance = (TextView) findViewById(R.id.distanceDetail);
    TextView mDuration = (TextView) findViewById(R.id.durationDetail);
    TextView mLocationA = (TextView) findViewById(R.id.locationA);
    TextView mLocationB = (TextView) findViewById(R.id.locationB);


    // Getting the values
    Intent i = getIntent();
    locationA = i.getStringExtra("locA");
    locationB = i.getStringExtra("locB");
    String distance = i.getStringExtra("distance");
    String duration = i.getStringExtra("duration");


    // initiate the values.
    mDistance.setText(distance);
    mDuration.setText(duration);
    mLocationA.setText(locationA);
    mLocationB.setText(locationB);


    drawOnMap();
}





public void drawOnMap(){

    latLngList = getIntent().getParcelableArrayListExtra("points");

    // Används för att rita ut marksen på kartan sedan, start och stop.
    // Get the first and last postion to write out the marks on map
    LatLng startLatLng = latLngList.get(0);
    LatLng endLatLng = latLngList.get(latLngList.size() - 1);

    // Zooms into the start position;
    mMap.moveCamera(CameraUpdateFactory.newLatLngZoom(startLatLng, 10));

    // Adding mark to start location
    mMap.addMarker(new MarkerOptions()
            .position(startLatLng)
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_GREEN))
            .title(locationA));

    // Adding mark to end location
    mMap.addMarker(new MarkerOptions()
            .position(endLatLng)
            .icon(BitmapDescriptorFactory.defaultMarker(BitmapDescriptorFactory.HUE_RED))
            .title(locationB));


    if (latLngList.size() > 0) {
        // Draw the route on map
        mMap.addPolyline(new PolylineOptions()
                .addAll(latLngList)
                .color(Color.argb(255, 55, 160, 255))
                .width(20));
    }
}



@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    UiSettings mapSettings = mMap.getUiSettings();
    mapSettings.setZoomControlsEnabled(true);
}

Catlog

java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.moveCamera(com.google.android.gms.maps.CameraUpdate)' on a null object reference at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2416) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616) Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void com.google.android.gms.maps.GoogleMap.moveCamera(com.google.android.gms.maps.CameraUpdate)' on a null object reference at com.example.rasmusjosefsson.rjcar.DetailActivity.drawOnMap(DetailActivity.java:113) at com.example.rasmusjosefsson.rjcar.DetailActivity.onCreate(DetailActivity.java:96) at android.app.Activity.performCreate(Activity.java:6237) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1107) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2369) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2476) at android.app.ActivityThread.-wrap11(ActivityThread.java) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1344) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148) at android.app.ActivityThread.main(ActivityThread.java:5417) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)

blackkara blackkara · Accepted Answer · 2016-05-26T16:34:41

Call drawOnMap method after map is ready.

@Override
public void onMapReady(GoogleMap googleMap) {
    mMap = googleMap;
    UiSettings mapSettings = mMap.getUiSettings();
    mapSettings.setZoomControlsEnabled(true);

    drawOnMap();
}

GoogleMap give me null when trying to draw on the map outside

2 Answers