尝试将数据从活动传递到片段Android时返回null指针

Question

I am trying to pass data from activity to a fragment. I have looked around at solutions but unable to get this to work for me. I've tried using the bundle but I am getting null pointer exception.

Activity Class:

public class RouteOutput extends AppCompatActivity {


private SectionsPagerAdapter mSectionsPagerAdapter;

/**
 * The {@link ViewPager} that will host the section contents.
 */
private ViewPager mViewPager;

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

    Bundle ways = getIntent().getExtras();
    if(ways==null) {
        return;
    }
    System.out.println("START LAT: " + ways.getDouble("start_lat"));



    ways.putDouble("start_lat", ways.getDouble("start_lat"));
    ways.putDouble("start_lon", ways.getDouble("start_lon"));
    ways.putStringArrayList("coords", ways.getStringArrayList("coords"));

    if(!(ways.getDouble("altend") == 0)) {
        ways.putDouble("altend_lat", ways.getDouble("altend_lat"));
        ways.putDouble("altend_lon", ways.getDouble("altend_lon"));
    }
    FragmentMapOutput frag = new FragmentMapOutput();
    frag.setArguments(ways);

And in my fragment class i have this:

View view = inflater.inflate(R.layout.fragment_map_output, container, false);
    MapboxAccountManager.start(getContext(), getString(R.string.access_token));

    mView = (MapView) view.findViewById(R.id.mapview);
    mView.onCreate(savedInstanceState);
    mView.getMapAsync(new OnMapReadyCallback() {
        @Override
        public void onMapReady(MapboxMap mapboxMap) {

            mMap = mapboxMap;

            Bundle bundle = getArguments();
            double startlat = bundle.getDouble("start_lat");
            System.out.println("BUNDLE: " + startlat);

I am using the android tablayout template and have two fragments in this activty.

The error i am getting is below:

W/System.err: java.lang.NullPointerException: Attempt to invoke virtual method 'double android.os.BaseBundle.getDouble(java.lang.String)' on a null object reference

Answer 1

Please, try to create a new Bundle instance that will go to fragment rather than using the one you receive in activity

Bundle newWays=new Bundle();
  Bundle ways = getIntent().getExtras();
if(ways==null) {
    return;
}


 newWays.putDouble("start_lat", ways.getDouble("start_lat"));
newWays.putDouble("start_lon", ways.getDouble("start_lon"));
newWays.putStringArrayList("coords", ways.getStringArrayList("coords"));

if(!(ways.getDouble("altend") == 0)) {
    newWays.putDouble("altend_lat", ways.getDouble("altend_lat"));
    newWays.putDouble("altend_lon", ways.getDouble("altend_lon"));
}
FragmentMapOutput frag = new FragmentMapOutput();
frag.setArguments(newWays);

Apart from this, I am not sure I see anything wrong, Hope it helps

Answer 2

Bundle is inside onMapReady method. It will be null.

You should get the data from bundle in onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstance)

and assign the data to member objects and then use in onMapReady.