完整错误跟踪:
07-09 15:04:39.552 32410-32410/com.example.junker.lectio E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.example.junker.lectio, PID: 32410
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.support.v7.widget.RecyclerView.setLayoutManager(android.support.v7.widget.RecyclerView$LayoutManager)' on a null object reference
at com.example.junker.lectio.OpgaveFragmentIndhold.onCreateView(OpgaveFragmentIndhold.java:103)
at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
at android.support.v4.app.FragmentManagerImpl.executePendingTransactions(FragmentManager.java:490)
at android.support.v4.app.FragmentStatePagerAdapter.finishUpdate(FragmentStatePagerAdapter.java:163)
at android.support.v4.view.ViewPager.populate(ViewPager.java:1105)
at android.support.v4.view.ViewPager.populate(ViewPager.java:951)
at android.support.v4.view.ViewPager.onMeasure(ViewPager.java:1473)
at android.view.View.measure(View.java:17430)
at android.widget.RelativeLayout.measureChildHorizontal(RelativeLayout.java:727)
at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:463)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17430)
at android.support.v4.widget.DrawerLayout.onMeasure(DrawerLayout.java:868)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1436)
at android.widget.LinearLayout.measureVertical(LinearLayout.java:722)
at android.widget.LinearLayout.onMeasure(LinearLayout.java:613)
at android.view.View.measure(View.java:17430)
at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:5463)
at android.widget.FrameLayout.onMeasure(FrameLayout.java:430)
at com.android.internal.policy.impl.PhoneWindow$DecorView.onMeasure(PhoneWindow.java:2560)
at android.view.View.measure(View.java:17430)
at android.view.ViewRootImpl.performMeasure(ViewRootImpl.java:2001)
at android.view.ViewRootImpl.measureHierarchy(ViewRootImpl.java:1166)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1372)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1054)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5779)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:767)
at android.view.Choreographer.doCallbacks(Choreographer.java:580)
at android.view.Choreographer.doFrame(Choreographer.java:550)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:753)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:135)
at android.app.ActivityTh
第一次使用recyclerview，并且已经为此奋斗了一整天。 已经尝试了很多东西，将附加 recyclerview 适配器从 on create 移动到 oncreateview，确保我声明一个布局管理器并检查代码是否有奇怪的错误。
OpgaveFragmentIndhold
public class OpgaveFragmentIndhold extends Fragment {
// 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 RecyclerView rvOpgave;
private RecyclerView.Adapter rvAdapter;
private RecyclerView.LayoutManager rvLayoutManager;
private OnFragmentInteractionListener mListener;
/**
* 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 OpgaveFragmentIndhold.
*/
// TODO: Rename and change types and number of parameters
public static OpgaveFragmentIndhold newInstance(String param1, String param2) {
OpgaveFragmentIndhold fragment = new OpgaveFragmentIndhold();
Bundle args = new Bundle();
args.putString(ARG_PARAM1, param1);
args.putString(ARG_PARAM2, param2);
fragment.setArguments(args);
return fragment;
}
public OpgaveFragmentIndhold() {
// Required empty public constructor
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getArguments() != null) {
mParam1 = getArguments().getString(ARG_PARAM1);
mParam2 = getArguments().getString(ARG_PARAM2);
}
}
//Use this part to get the data from lectio and input it here
private ArrayList<Opgave> getOpgaveInfo() {
ArrayList<Opgave> items = new ArrayList<>();
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
items.add(new Opgave("Opgave titel", "15", "3 dage og 15 timer","link"));
return items;
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout.fragment_skema, container, false);
rvOpgave = (RecyclerView) rootView.findViewById(R.id.opgave_recycler_view);
rvAdapter = new OpgaveRecyclerViewAdapter(getOpgaveInfo());
rvLayoutManager = new LinearLayoutManager(getActivity());
rvOpgave.setLayoutManager(rvLayoutManager);
rvOpgave.setAdapter(rvAdapter);
return rootView;
}
@Override
public void onViewCreated(View view, Bundle savedInstanceState) {
}
// TODO: Rename method, update argument and hook method into UI event
public void onButtonPressed(Uri uri) {
if (mListener != null) {
mListener.onFragmentInteraction(uri);
}
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
}
@Override
public void onDetach() {
super.onDetach();
mListener = null;
}
/**
* 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 OnFragmentInteractionListener {
// TODO: Update argument type and name
public void onFragmentInteraction(Uri uri);
}
}
OpgaveRecyclerViewAdapter
public class OpgaveRecyclerViewAdapter extends RecyclerView.Adapter<OpgaveRecyclerViewAdapter.ViewHolder> {
private ArrayList<Opgave> opgaver;
public OpgaveRecyclerViewAdapter(ArrayList<Opgave> opgaver){
this.opgaver = opgaver;
}
public class ViewHolder extends RecyclerView.ViewHolder {
public TextView opgaveTitel;
public TextView opgaveTidspunkt;
public TextView opgaveUge;
public ViewHolder(View itemView) {
super(itemView);
this.opgaveTitel =(TextView) itemView.findViewById(R.id.opgaveTitel);
this.opgaveTidspunkt =(TextView) itemView.findViewById(R.id.opgaveTidspunkt);
this.opgaveUge =(TextView) itemView.findViewById(R.id.opgaveUge);
}
}
@Override
public void onBindViewHolder(OpgaveRecyclerViewAdapter.ViewHolder holder, int position) {
// Get the data model based on position
Opgave opgave = opgaver.get(position);
// Set item views based on the data model
holder.opgaveTitel.setText(opgave.opgaveTitel);
holder.opgaveTidspunkt.setText(opgave.opgaveTidspunkt);
holder.opgaveUge.setText(opgave.opgaveUge);
}
@Override
public OpgaveRecyclerViewAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View itemView = LayoutInflater.from(parent.getContext()).
inflate(R.layout.opgave_item, parent, false);
// Return a new holder instance
return new OpgaveRecyclerViewAdapter.ViewHolder(itemView);
}
@Override
public int getItemCount() {
return opgaver.size();
}
}
opgave 类
public class Opgave {
public String opgaveTitel;
public String opgaveUge;
public String opgaveTidspunkt;
public String opgaveId;
public Opgave(String opgaveTitel, String opgaveUge, String opgaveTidspunkt, String opgaveId) {
this.opgaveTitel = opgaveTitel;
this.opgaveUge = opgaveUge;
this.opgaveTidspunkt = opgaveTidspunkt;
this.opgaveId = opgaveId;
}
}
opgave_fragment.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent" >
<android.support.v7.widget.RecyclerView
android:id="@+id/opgave_recycler_view"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
</RelativeLayout>
<?xml version="1.0" encoding="utf-8"?>
<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:textAppearance="?android:attr/textAppearanceLarge"
android:id="@+id/opgaveTitel"
android:text="titel"
android:layout_gravity="center_horizontal" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textSize="25sp"
android:text="15"
android:id="@+id/opgaveUge" />
<TextView
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:textAppearance="?android:attr/textAppearanceMedium"
android:text="tidspunkt"
android:id="@+id/opgaveTidspunkt"
android:layout_marginLeft="10dp"
android:layout_gravity="right" />
</LinearLayout>
最佳答案
您正在夸大错误的 xml 文件。 变化:
View rootView = inflater.inflate(R.layout.fragment_skema, container, false);
至
View rootView = inflater.inflate(R.layout.opgave_fragment, container, false);
关于java - 在 fragment 中设置布局管理器时，在 Recyclerview 上出现空指针异常，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31327667/