我正在尝试将我的NestedScrollView放在我的MapFragment上,但是当我尝试时,会出现此错误:
尝试在空对象引用上调用虚拟方法'android.view.View android.support.v4.widget.NestedScrollView.findViewById(int)'
这是我的MapFragment.java文件
package com.example.alexandre.list.fragments;
import android.content.Context;
import android.os.Bundle;
import android.support.v4.app.Fragment;
import android.support.v4.widget.NestedScrollView;
import android.support.v7.app.AppCompatActivity;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import com.example.alexandre.list.MainActivity;
import com.example.alexandre.list.R;
import com.google.android.gms.maps.CameraUpdateFactory;
import com.google.android.gms.maps.GoogleMap;
import com.google.android.gms.maps.MapView;
import com.google.android.gms.maps.MapsInitializer;
import com.google.android.gms.maps.OnMapReadyCallback;
import com.google.android.gms.maps.SupportMapFragment;
import com.google.android.gms.maps.model.CameraPosition;
import com.google.android.gms.maps.model.LatLng;
import com.google.android.gms.maps.model.Marker;
import com.google.android.gms.maps.model.MarkerOptions;
/**
* A simple {@link Fragment} subclass.
* Activities that contain this fragment must implement the
* {@link OnMapClickListener} interface
* to handle interaction events.
* Use the {@link MapFragment#newInstance} factory method to
* create an instance of this fragment.
*/
public class MapFragment extends Fragment implements OnMapReadyCallback {
// TODO: Rename parameter arguments, choose names that match
// the fragment initialization parameters, e.g. ARG_ITEM_NUMBER
private static final String ARG_PARAM1 = "param1";
private static final String ARG_PARAM2 = "param2";
// TODO: Rename and change types of parameters
private String mParam1;
private String mParam2;
private GoogleMap mGoogleMap;
private MapView mMapView;
private OnMapClickListener mListener;
public MapFragment() {
// Required empty public constructor
}
/**
* Use this factory method to create a new instance of
* this fragment using the provided parameters.
*
* @param param1 Parameter 1.
* @param param2 Parameter 2.
* @return A new instance of fragment MapFragment.
*/
// TODO: Rename and change types and number of parameters
public static MapFragment newInstance(String param1, String param2) {
MapFragment fragment = new MapFragment();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// Inflate the layout for this fragment
View view = inflater.inflate(R.layout.fragment_map, container, false);
bindViews(view, savedInstanceState);
return view;
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed() {
if (mListener != null) {
mListener.onMapClick();
}
}
@Override
public void onAttach(Context context) {
super.onAttach(context);
if (context instanceof OnMapClickListener) {
mListener = (OnMapClickListener) context;
} else {
throw new RuntimeException(context.toString()
+ " must implement OnTweetListClickListener");
}
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
private void bindViews(View view, Bundle savedInstanceState) {
mMapView = view.findViewById(R.id.map);
mMapView.onCreate(savedInstanceState);
mMapView.getMapAsync(this);
}
@Override
public void onResume() {
super.onResume();
mMapView.onResume();
}
@Override
public void onDestroy() {
super.onDestroy();
mMapView.onDestroy();
}
@Override
public void onMapReady(GoogleMap googleMap) {
mGoogleMap = googleMap;
LatLng castlePos = new LatLng(45.209299, 5.659144);
LatLng treePos = new LatLng(MainActivity.posx, MainActivity.posy);
CameraPosition liberty = CameraPosition.builder().target(castlePos).zoom(17)/*.bearing(0).tilt(0)*/.build();
Marker marker = mGoogleMap.addMarker(new MarkerOptions()
.position(treePos)
.title("Test du cèdre du Liban")
.snippet("Libani"));
marker.hideInfoWindow();
mGoogleMap.setOnMarkerClickListener(
new GoogleMap.OnMarkerClickListener() {
@Override
public boolean onMarkerClick(Marker marker) {
((AppCompatActivity) getActivity()).getSupportActionBar().hide();
NestedScrollView nestedScrollView = null;
nestedScrollView = (NestedScrollView) nestedScrollView.findViewById(R.id.bottom_sheet);
nestedScrollView.setVisibility(View.VISIBLE);
return false;
}
}
);
mGoogleMap.moveCamera(CameraUpdateFactory.newCameraPosition(liberty));
mGoogleMap.setMapType(GoogleMap.MAP_TYPE_NORMAL);
}
/**
* This interface must be implemented by activities that contain this
* fragment to allow an interaction in this fragment to be communicated
* to the activity and potentially other fragments contained in that
* activity.
* <p>
* See the Android Training lesson <a href=
* "http://developer.android.com/training/basics/fragments/communicating.html"
* >Communicating with Other Fragments</a> for more information.
*/
public interface OnMapClickListener {
void onMapClick();
}
}
看起来像R.id.nestedScrollView返回NULL,但为什么?
谢谢!
答案 0 :(得分:0)
将此代码NestedScrollView nestedScrollView;
移至顶部,并在onCreateView()
方法中引用该代码。像这样:
nestedScrollView = (NestedScrollView) view.findViewById(R.id.bottom_sheet);
。现在,您可以在片段中的任何方法中使用它,包括onMarkerClick()
。
您收到NPE错误,因为您的代码告诉Dalvik计算机它应该在空视图NestedScrollView
中查找NestedScrollView nestedScrollView= null
。
希望它有所帮助。