到 recyclerview 的 Firebase 数据显示错误 - RecyclerView：android 中没有附加适配器

Question

您好，我想将图像从 Firebase 获取到内存中。当我调试我的代码时，它首先返回视图，然后返回 usersPhotoRef.addValueEventListener() 并将 mPhotoArrayList 的大小打印为 0。最后返回 photoRef.getBytes()#addOnSuccessListener() 并将位图放入 ArrayList。我认为我的代码应该更正，这样我就可以将mPhotoArrayList 传递给适配器。我该怎么做或必须进行哪些更改？

这段代码的输出：

2019-06-30 15:01:00.130 12154-12154/com.newstrange.worklog E/RecyclerView: No adapter attached; skipping layout
2019-06-30 15:01:00.134 12154-12158/com.newstrange.worklog I/art: Do partial code cache collection, code=24KB, data=30KB
2019-06-30 15:01:00.135 12154-12158/com.newstrange.worklog I/art: After code cache collection, code=23KB, data=30KB
2019-06-30 15:01:00.135 12154-12158/com.newstrange.worklog I/art: Increasing code cache capacity to 128KB
2019-06-30 15:01:00.151 12154-12154/com.newstrange.worklog I/IMAGE_NAME: asdasd_giris_25.54.47_29.Mayıs.2019
2019-06-30 15:01:00.169 12154-12154/com.newstrange.worklog I/SELFIES: 0
2019-06-30 15:01:00.169 12154-12154/com.newstrange.worklog I/IMAGE_NAME: fdsafdas_giris_25.55.4_29.Mayıs.2019
2019-06-30 15:01:00.170 12154-12154/com.newstrange.worklog I/SELFIES: 0
2019-06-30 15:01:00.170 12154-12154/com.newstrange.worklog I/IMAGE_NAME: sdf_cikis_8.44.32_30.Mayıs.2019
2019-06-30 15:01:00.173 12154-12154/com.newstrange.worklog I/SELFIES: 0
2019-06-30 15:01:00.842 12154-12154/com.newstrange.worklog I/GET_BITMAP: 1
2019-06-30 15:01:00.846 12154-12154/com.newstrange.worklog I/GET_BITMAP: 2
2019-06-30 15:01:00.858 12154-12154/com.newstrange.worklog I/GET_BITMAP: 3

代码：

package com.newstrange.worklog;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.support.v7.widget.DefaultItemAnimator;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Toast;

import com.google.android.gms.tasks.OnCompleteListener;
import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;
import com.google.firebase.storage.FirebaseStorage;
import com.google.firebase.storage.StorageReference;

import java.io.IOException;
import java.util.ArrayList;

public class ListSelfiesFragment extends Fragment {

    private FirebaseStorage mStorageIns;
    private FirebaseDatabase mDatabaseIns;
    private RecyclerView mRecyclerView;
    private GridLayoutManager mLayoutManager;

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

        mDatabaseIns = FirebaseDatabase.getInstance(); // DATABASE

        mStorageIns = FirebaseStorage.getInstance(); // STORAGE

        View view = inflater.inflate(R.layout.fragment_list_selfies, container, false);
        mRecyclerView = view.findViewById(R.id.selfies_recyclerview);

        //initialize lists
        final ArrayList<String> mPhotoIds = new ArrayList<>();
        final ArrayList<Bitmap> mPhotoArrayList = new ArrayList<>();

        //get names
        DatabaseReference usersPhotoRef = mDatabaseIns.getReference().child("storeIDs");

        usersPhotoRef.addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                final long ONE_MEGABYTE = 1024 * 1024;
                for (DataSnapshot uniqueKeySnapshot : dataSnapshot.getChildren()) {

                    String image_name = uniqueKeySnapshot.getValue(String.class);
                    Log.i("IMAGE_NAME", image_name);
                    mPhotoIds.add(image_name);
                    String photoId = image_name + ".png";
                    StorageReference photoRef = mStorageIns.getReference().child("images/" + photoId);
                    photoRef.getBytes(ONE_MEGABYTE).addOnSuccessListener(new OnSuccessListener<byte[]>() {
                        @Override
                        public void onSuccess(byte[] bytes) {
                            Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                            mPhotoArrayList.add(bitmap);
                            Log.i("GET_BITMAP", String.valueOf(mPhotoArrayList.size()));
                        }
                    }).addOnFailureListener(new OnFailureListener() {
                        @Override
                        public void onFailure(@NonNull Exception e) {
                            Log.i("SELFIEFRAGMENT", e.getMessage());
                        }
                    });
                    Log.i("SELFIES", String.valueOf(mPhotoArrayList.size()));
                }

                SelfiesAdapter selfiesAdapter = new SelfiesAdapter(getActivity(), mPhotoArrayList, mPhotoIds);
                mRecyclerView.setAdapter(selfiesAdapter);

                mLayoutManager = new GridLayoutManager(getActivity(), 2);
                mRecyclerView.setLayoutManager(mLayoutManager);
                mRecyclerView.setItemAnimator(new DefaultItemAnimator());
            }
            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Log.i("SELFIEFRAGMENT", databaseError.getMessage());
            }
        });

        return view;
    }

}

Answer 1

每次向mPhotoArrayList 添加照片时，都需要通过调用notifyDataSetChanged() 让适配器知道其数据集已更改。然后适配器将重新渲染视图。

usersPhotoRef.addValueEventListener(new ValueEventListener() {
    @Override
    public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
        final long ONE_MEGABYTE = 1024 * 1024;
        for (DataSnapshot uniqueKeySnapshot : dataSnapshot.getChildren()) {

            String image_name = uniqueKeySnapshot.getValue(String.class);
            Log.i("IMAGE_NAME", image_name);
            mPhotoIds.add(image_name);
            String photoId = image_name + ".png";
            StorageReference photoRef = mStorageIns.getReference().child("images/" + photoId);
            photoRef.getBytes(ONE_MEGABYTE).addOnSuccessListener(new OnSuccessListener<byte[]>() {
                @Override
                public void onSuccess(byte[] bytes) {
                    Bitmap bitmap = BitmapFactory.decodeByteArray(bytes, 0, bytes.length);
                    mPhotoArrayList.add(bitmap);
                    Log.i("GET_BITMAP", String.valueOf(mPhotoArrayList.size()));

                    selfiesAdapter.notifyDataSetChanged();
                }
            }).addOnFailureListener(new OnFailureListener() {
                @Override
                public void onFailure(@NonNull Exception e) {
                    Log.i("SELFIEFRAGMENT", e.getMessage());
                }
            });
            Log.i("SELFIES", String.valueOf(mPhotoArrayList.size()));
        }

要让回调找到适配器，您需要将其声明为 final：

        final SelfiesAdapter selfiesAdapter = new SelfiesAdapter(getActivity(), mPhotoArrayList, mPhotoIds);