回收站视图未显示在片段中

Question

由于某种原因，我将活动更改为片段，但现在我的回收站视图未显示我还检查了我想在回收站视图上显示的 ArrayList，它不是空的。 相同的代码在另一个活动和片段中工作，但不在此片段中。 请有人帮帮我！！ 先感谢您

我的片段代码

public class HomeSkillsFragment extends Fragment {

private EditText Search;
private ImageView back;
private RecyclerView recyclerView;
private ArrayList<Post> postItem;
private postAdapter adapter;
private GridLayoutManager gridLayoutManager;
private DatabaseReference reference;
private BottomNavigationVisibility bottomNavigationVisibility;

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {
    // Inflate the layout for this fragment
    return inflater.inflate(R.layout.fragment_home_skills, container, false);
}


@Override
public void onActivityCreated(@Nullable Bundle savedInstanceState) {
    super.onActivityCreated(savedInstanceState);

    bottomNavigationVisibility = new BottomNavigationVisibility(getActivity());
    bottomNavigationVisibility.hideBottomNavigation();

    //init Views
    Search = getActivity().findViewById(R.id.search_editText);
    back = getActivity().findViewById(R.id.back);
    recyclerView = getActivity().findViewById(R.id.recyclerView);
    gridLayoutManager = new GridLayoutManager(getContext(),2,GridLayoutManager.VERTICAL,false);
    recyclerView.setLayoutManager(gridLayoutManager);

    //getting Data from Database
    getDataFromDB();

    //click handle, back
    back.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            bottomNavigationVisibility.showBottomNavigation();
            NavController navController = Navigation.findNavController(getActivity(), R.id.nav_host_fragment);
            navController.navigate(R.id.navigation_home);

        }
    });
}


private void getDataFromDB(){

    postItem = new ArrayList<>();
    //initialize database
    reference = FirebaseDatabase.getInstance().getReference("Posts");
    reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot snapshot) {
                    for(DataSnapshot dataSnapshot: snapshot.getChildren()){
                        Post post = dataSnapshot.getValue(Post.class);
                        if(post.getCategory().equals("Skills, M" ) || post.getCategory().equals("Skills, S"))
                            postItem.add(post);
                    }

                    adapter = new postAdapter(getContext(),postItem);
                    recyclerView.setAdapter(adapter);
                }

                @Override
                public void onCancelled(@NonNull DatabaseError error) {
                    Toast.makeText(getContext(),"Something went Wrong",Toast.LENGTH_SHORT).show();

                }
            });

}

}

我的适配器代码

public class postAdapter extends RecyclerView.Adapter<postAdapter.PostViewHolder> {

LayoutInflater mInflater;
private ArrayList<Post> mPost;
Context context;

public postAdapter(Context context, ArrayList<Post> posts) {
    mInflater = LayoutInflater.from(context);
    this.mPost = posts;
    this.context=context;
}

@NonNull
@Override
public PostViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
    View itemView = mInflater.inflate(R.layout.list_item,parent,false);
    return new PostViewHolder(itemView,this);
}

@RequiresApi(api = Build.VERSION_CODES.M)
@Override
public void onBindViewHolder(@NonNull PostViewHolder holder, int position) {

    //setting post title
    Post currentPost = mPost.get(position);
    holder.itemNameTextView.setText(currentPost.getPost_Title());

    //setting InExchange
    if(currentPost.getCategory().equals("Skills, M") || currentPost.getCategory().equals("Educational Accessories, M")){
        holder.inExchangeTextView.setText("Rs. " + currentPost.getIn_Exchange());
        holder.inExchangeTextView.setTextColor(context.getColor(R.color.blue));
        holder.exchangeIcon.setVisibility(View.VISIBLE);
    }
    else if(currentPost.getCategory().equals("Skills, S") || currentPost.getCategory().equals("Educational Accessories, A")){
        holder.inExchangeTextView.setText(currentPost.getIn_Exchange());
        holder.inExchangeTextView.setTextColor(context.getColor(R.color.blue));
        holder.exchangeIcon.setVisibility(View.VISIBLE);
    }
    else{
        holder.inExchangeTextView.setText(currentPost.getIn_Exchange());
        holder.inExchangeTextView.setTextColor(context.getColor(R.color.green));
        holder.exchangeIcon.setVisibility(View.INVISIBLE);
    }

    //setting image
    Picasso.get().load(currentPost.getImage_Url_1()).into(holder.image);
    holder.image.setClipToOutline(true);

    //setting institution name
    FirebaseDatabase.getInstance().getReference("Users/"+currentPost.getUid()+"/").getRef().addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot snapshot) {
            for (DataSnapshot dataSnapshot : snapshot.getChildren()) {
                holder.institutionName.setText(snapshot.child("institution").getValue(String.class));
            }
        }
        @Override
        public void onCancelled(@NonNull DatabaseError error) {
            Toast.makeText(context,"Something went wrong",Toast.LENGTH_SHORT).show();

        }
    });

    //handle click of item
    holder.itemView.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            Bundle bundle = new Bundle();
            bundle.putSerializable("currentPost", currentPost);
            Navigation.findNavController(view).navigate(R.id.action_navigation_home_to_homeDetailFragment, bundle);
        }
    });

}

@Override
public int getItemCount() {
    return mPost.size();
}

class PostViewHolder extends  RecyclerView.ViewHolder{

    TextView itemNameTextView;
    TextView inExchangeTextView ;
    TextView institutionName;
    ImageView image, exchangeIcon ;
    RecyclerView.Adapter mAdapter;

    public PostViewHolder(@NonNull View itemView, postAdapter adapter) {
        super(itemView);
        itemNameTextView = itemView.findViewById(R.id.itemName_TextView);
        inExchangeTextView = itemView.findViewById(R.id.inExchange_TextView);
        image = itemView.findViewById(R.id.imageView);
        institutionName = itemView.findViewById(R.id.institutionName);
        exchangeIcon = itemView.findViewById(R.id.exchange_icon);
        mAdapter = adapter;
    }
}

}

我的 Xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".fragments.home.HomeSkillsFragment">


    <androidx.constraintlayout.widget.ConstraintLayout
        android:id="@+id/constraintLayoutTop"
        android:layout_width="match_parent"
        android:layout_height="@dimen/_130sdp"
        android:background="@drawable/top_background_rounded"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent">

        <ImageView
            android:id="@+id/back"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="@dimen/_10sdp"
            android:layout_marginStart="@dimen/_12sdp"
            android:foreground="?android:attr/selectableItemBackgroundBorderless"
            android:src="@drawable/arrow_back"
            android:padding="@dimen/_8sdp"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <EditText
            android:id="@+id/search_editText"
            style="@style/searchView"
            android:layout_width="0dp"
            android:layout_height="@dimen/_35sdp"
            android:layout_marginStart="@dimen/_10sdp"
            android:layout_marginTop="@dimen/_8sdp"
            android:inputType="text"
            android:includeFontPadding="false"
            android:singleLine="true"
            android:layout_marginEnd="@dimen/_16sdp"
            android:layout_marginBottom="@dimen/main_start_end_margin"
            android:hint="Search"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toEndOf="@id/back"
            app:layout_constraintTop_toTopOf="parent" />



    <ImageView
        android:id="@+id/skills_imageView"
        android:layout_width="@dimen/_50sdp"
        android:layout_height="@dimen/_50sdp"
        android:background="@drawable/searchview_bg"
        android:src="@drawable/ic_skills"
        android:scaleType="centerInside"
        android:layout_marginTop="@dimen/_8sdp"
        app:layout_constraintTop_toBottomOf="@id/search_editText"
        app:layout_constraintEnd_toEndOf="@+id/constraintLayoutTop"
        app:layout_constraintStart_toStartOf="@+id/constraintLayoutTop" />
<TextView
    android:id="@+id/skills_TextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginTop="@dimen/_4sdp"
    android:fontFamily="@font/poppins_regular"
    android:text="Skills"
    android:textColor="@android:color/black"
    android:textSize="@dimen/_12ssp"
    android:includeFontPadding="false"
    app:layout_constraintTop_toBottomOf="@id/skills_imageView"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintEnd_toEndOf="parent"/>

    </androidx.constraintlayout.widget.ConstraintLayout>


<TextView
    android:id="@+id/inExchange_TextView"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="In Exchange"
    android:textSize="@dimen/_10ssp"
    android:textColor="@color/black"
    android:fontFamily="@font/poppins_medium"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintTop_toBottomOf="@id/constraintLayoutTop"
    android:layout_marginTop="@dimen/_8sdp" />

<RadioGroup
    android:id="@+id/radioGroup"
    android:layout_width="wrap_content"
    android:layout_height="@dimen/_20sdp"
    app:layout_constraintTop_toBottomOf="@id/inExchange_TextView"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    android:orientation="horizontal">

    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="See All"
        android:scaleX="0.9"
        android:scaleY="0.9"
        android:textStyle="bold"
        style="@style/radioButton"
        android:fontFamily="@font/poppins_medium"
        android:includeFontPadding="false"
        android:id="@+id/radioButtonAll"
        android:checked="true"
        android:textSize="@dimen/_10sdp" />

    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Give Money"
        style="@style/radioButton"
        android:scaleX="0.9"
        android:scaleY="0.9"
        android:textStyle="bold"
        android:includeFontPadding="false"
        android:fontFamily="@font/poppins_medium"
        android:id="@+id/radioButtonMoney"
        android:checked="false"
        android:textSize="@dimen/_10sdp" />

    <RadioButton
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:includeFontPadding="false"
        android:scaleX="0.9"
        android:scaleY="0.9"
        android:text="Teach Other Skill"
        style="@style/radioButton"
        android:textStyle="bold"
        android:fontFamily="@font/poppins_medium"
        android:id="@+id/radioButtonSkill"
        android:checked="false"
        android:textSize="@dimen/_10sdp" />
</RadioGroup>

<androidx.recyclerview.widget.RecyclerView
    android:id="@+id/recyclerView"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_marginTop="@dimen/_10sdp"
    android:paddingLeft="@dimen/_12sdp"
    android:paddingRight="@dimen/_12sdp"
    android:paddingTop="@dimen/_8sdp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toBottomOf="@id/radioGroup"
    app:layout_constraintVertical_weight="1" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

在您的代码中，您将尝试从活动中获取视图，而不是从片段中获取视图。 而不是onActivityCreated使用onViewCreated

    Search = getActivity().findViewById(R.id.search_editText);
    back = getActivity().findViewById(R.id.back);
    recyclerView = getActivity().findViewById(R.id.recyclerView);

更新您的 HomeSkillFragment class。

public class HomeSkillsFragment extends Fragment {

    private EditText Search;
    private ImageView back;
    private RecyclerView recyclerView;
    private ArrayList<Post> postItem;
    private postAdapter adapter;
    private GridLayoutManager gridLayoutManager;
    private DatabaseReference reference;
    private BottomNavigationVisibility bottomNavigationVisibility;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_home_skills, container, false);
    }


    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
        super.onViewCreated(view, savedInstanceState);
        
        bottomNavigationVisibility = new BottomNavigationVisibility(getActivity());
        bottomNavigationVisibility.hideBottomNavigation();

        //init Views
        Search = view.findViewById(R.id.search_editText);
        back = view.findViewById(R.id.back);
        recyclerView = view.findViewById(R.id.recyclerView);
        gridLayoutManager = new GridLayoutManager(getContext(), 2, GridLayoutManager.VERTICAL, false);
        recyclerView.setLayoutManager(gridLayoutManager);

        //getting Data from Database
        getDataFromDB();

        //click handle, back
        back.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                bottomNavigationVisibility.showBottomNavigation();
                NavController navController = Navigation.findNavController(getActivity(), R.id.nav_host_fragment);
                navController.navigate(R.id.navigation_home);

            }
        });
    }

    private void getDataFromDB() {

        postItem = new ArrayList<>();
        //initialize database
        reference = FirebaseDatabase.getInstance().getReference("Posts");
        reference.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                for (DataSnapshot dataSnapshot : snapshot.getChildren()) {
                    Post post = dataSnapshot.getValue(Post.class);
                    if (post.getCategory().equals("Skills, M") || post.getCategory().equals("Skills, S"))
                        postItem.add(post);
                }

                adapter = new postAdapter(getContext(), postItem);
                recyclerView.setAdapter(adapter);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Toast.makeText(getContext(), "Something went Wrong", Toast.LENGTH_SHORT).show();

            }
        });
    }
}