Firebase Recycler查看项目之间的填充

Question

我一直在尝试在Firebase RecyclerView项之间进行填充。我尝试使用ItemDecoration，但它仅适用于RecyclerView的第一项。如果您能指出我的错误，将对您有很大的帮助。

这就是我得到的

我想要得到的是一个布局，其中每个recyclerview项之间都有填充，以便我可以看到每个项的阴影。

这是我的Java代码，使用Firebase RecyclerView加载项目。

public class CommunityFragment extends Fragment {
    private static final String KEY_RECYCLER_STATE = "";
    private RecyclerView mConvList;
    private DatabaseReference mConvDatabase;
    private DatabaseReference mUsersDatabase;
    private DatabaseReference mMessageDatabase;
    private Bundle mBundleRecyclerViewState;
    private Parcelable mListState;
    private static final String TAG = "ChatsFragment";

    public CommunityFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {


        View mMainView = inflater.inflate(R.layout.fragment_chats, container, false);

        mConvList = (RecyclerView) mMainView.findViewById(R.id.conv_list);
        FirebaseAuth mAuth = FirebaseAuth.getInstance();

        String mCurrent_user_id = Objects.requireNonNull(mAuth.getCurrentUser()).getUid();

        mConvDatabase = FirebaseDatabase.getInstance().getReference().child("Chat").child(mCurrent_user_id);
        mConvDatabase.keepSynced(true);

        mUsersDatabase = FirebaseDatabase.getInstance().getReference().child("Users");
        mUsersDatabase.keepSynced(true);

        mMessageDatabase = FirebaseDatabase.getInstance().getReference().child("messages").child(mCurrent_user_id);
        mMessageDatabase.keepSynced(true);

        mConvList = mMainView.findViewById(R.id.conv_list);
        mConvList.setHasFixedSize(true);
        mConvList.setLayoutManager(new LinearLayoutManager(getContext()));

        // Inflate the layout for this fragment
        return mMainView;
    }

    @Override
    public void onStart() {
        super.onStart();

        Query conversationQuery = mConvDatabase.orderByChild("timestamp");

        FirebaseRecyclerOptions<Conv> friendsFirebaseRecyclerOptions = new FirebaseRecyclerOptions.Builder<Conv>()
                .setQuery(conversationQuery, Conv.class)
                .build();

        FirebaseRecyclerAdapter<Conv, ConvViewHolder> firebaseConvAdapter = new FirebaseRecyclerAdapter<Conv, ConvViewHolder>(friendsFirebaseRecyclerOptions) {
            @Override
            protected void onBindViewHolder(@NonNull final ConvViewHolder holder, int position, @NonNull final Conv model) {

                final String list_user_id = getRef(position).getKey();

                assert list_user_id != null;
                Query lastMessageQuery = mMessageDatabase.child(list_user_id).limitToLast(1);

                lastMessageQuery.addChildEventListener(new ChildEventListener() {

                    @Override
                    public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
                        String data = Objects.requireNonNull(dataSnapshot.child("message").getValue()).toString();
                        String seen_ = Objects.requireNonNull(dataSnapshot.child("seen").getValue()).toString();
                        holder.setMessage(data, Boolean.parseBoolean(seen_));

                    }

                    @Override
                    public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

                    }

                    @Override
                    public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {

                    }

                    @Override
                    public void onChildMoved(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {

                    }

                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });

                mUsersDatabase.child(list_user_id).addValueEventListener(new ValueEventListener() {
                    @Override
                    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                        final String userName = dataSnapshot.child("Name").getValue().toString();
                        holder.setName(userName);
                        holder.mView.setOnClickListener(new View.OnClickListener() {
                            @Override
                            public void onClick(View v) {
                                Intent chatIntent = new Intent(getContext(), ChatActivity.class);
                                chatIntent.putExtra("user_id", list_user_id);
                                chatIntent.putExtra("user_name",userName);
                                startActivity(chatIntent);
                            }
                        });

                    }


                    @Override
                    public void onCancelled(@NonNull DatabaseError databaseError) {

                    }
                });

            }
            @NonNull
            @Override
            public ConvViewHolder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
                View view = LayoutInflater.from(viewGroup.getContext()).inflate(R.layout.single_q_layout, viewGroup, false);
                return new ConvViewHolder(view);
            }
        };
        mConvList.addItemDecoration(new PaddingItemDecoration(200));
        firebaseConvAdapter.startListening();
        mConvList.setAdapter(firebaseConvAdapter);

    }

    public void onPause(){
        super.onPause();
        mBundleRecyclerViewState = new Bundle();
        mListState = mConvList.getLayoutManager().onSaveInstanceState();
        mBundleRecyclerViewState.putParcelable(KEY_RECYCLER_STATE, mListState);
    }

    public void onResume(){
        super.onResume();
        if (mBundleRecyclerViewState != null) {
            new Handler().postDelayed(new Runnable() {

                @Override
                public void run() {
                    mListState = mBundleRecyclerViewState.getParcelable(KEY_RECYCLER_STATE);
                    mConvList.getLayoutManager().onRestoreInstanceState(mListState);

                }
            }, 50);
        }
        mConvList.setLayoutManager(new LinearLayoutManager(getContext()));
    }

    public  class ConvViewHolder extends RecyclerView.ViewHolder {

        View mView;

        public ConvViewHolder(@NonNull View itemView) {
            super(itemView);
            mView = itemView;
        }

        public void setName(String name){
            TextView userNameView = (TextView) mView.findViewById(R.id.question_title);
            userNameView.setText(name);
        }

        public void setMessage(String message, boolean isSeen) {
            TextView userStatusView = (TextView) mView.findViewById(R.id.question_catergory);

            //Log.i("textData", "State is " + isSeen);
            if(!isSeen){
                userStatusView.setText("New Message");
                userStatusView.setTypeface(userStatusView.getTypeface(), Typeface.BOLD);
            }else{
                userStatusView.setText("No New Messages");
                userStatusView.setTypeface(userStatusView.getTypeface(), Typeface.NORMAL);
            }

        }
    }

}

这是我的PaddingItemDecoration类。

public class PaddingItemDecoration extends RecyclerView.ItemDecoration {
    private final int size;

    public PaddingItemDecoration(int size) {
        this.size = size;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        super.getItemOffsets(outRect, view, parent, state);

        // Apply offset only to first item
        if (parent.getChildAdapterPosition(view) == 0) {
            outRect.top += size;
            outRect.bottom += size;

        }
    }

这是我的适配器的XML文件，我用于加载RecyclerView项。

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/relativeLayout3"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:background="@drawable/message_text_background"
    android:elevation="4dp"
    android:padding="10dp">

    <TextView
        android:id="@+id/question_title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:padding="10dp"
        android:text="Display Name"
        android:textColor="#020202"
        android:textSize="18sp"
        android:textStyle="bold"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <TextView
        android:id="@+id/question_catergory"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="16dp"
        android:layout_marginTop="8dp"
        android:text="catergory"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/question_title" />

    <TextView
        android:id="@+id/counter_value"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:text="counter"
        app:layout_constraintEnd_toStartOf="@+id/answers_given"
        app:layout_constraintTop_toBottomOf="@+id/question_title" />

    <TextView
        android:id="@+id/answers_given"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginTop="8dp"
        android:layout_marginEnd="8dp"
        android:text="answers"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/question_title" />

</androidx.constraintlayout.widget.ConstraintLayout>

Answer 1

而不是使用此PaddingItemDecoration，只需在适配器的XML文件周围添加边距

正如我所看到的，您已经在“父约束”布局（尝试边距）中添加了填充，因此，只需删除装饰类，然后仅尝试将列表打印到屏幕上，就可以了。

下图是我的应用程序中适配器的ListItem布局的示例，您的外观也应该像这样。

尝试增加边距10dp

如果无法这样做，请尝试隐含this文章中显示的方式。