Question

我的代码需要一些帮助。我无法解决问题。我正在使用日志进行调试。 onDataChange（）方法Log.i("SELFIES", image_name);内的其中一个，另外两个Log.i("SELFIEFRAGMENT", String.valueOf(mPhotoIds.size()));不在此方法之内。

问题是，它最初没有进入onDataChange方法，而是经过它，打印数组的大小，返回视图。之后，它返回并进入方法并打印获取的数据，然后完成操作（我的目标是在其他方法中使用mPhotoIds数组，但会出现此问题）。

调试器控制台输出：

    I/SELFIEFRAGMENT: Array size is : 0
    I/SELFIEFRAGMENT: Array size is : 0
    I/Choreographer: Skipped 998 frames!  The application may be doing too much work on its main thread.
    I/SELFIES: asdasd_giris_25.54.47_29.Mayıs.2019
    I/SELFIES: fdsafdas_giris_25.55.4_29.Mayıs.2019
    I/SELFIES: sdf_cikis_8.44.32_30.Mayıs.2019

我的代码：

package com.newstrange.worklog;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
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 com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
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.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) {

                for (DataSnapshot uniqueKeySnapshot : dataSnapshot.getChildren()) {
                    String image_name = uniqueKeySnapshot.getValue(String.class);
                    Log.i("SELFIES", image_name); // PRINTING when everything is finished
                    mPhotoIds.add(image_name);
                }
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Log.i("SELFIEFRAGMENT", databaseError.getMessage());
            }
        });

        Log.i("SELFIEFRAGMENT", "Array size is : " +mPhotoIds.size()); // PRINTS 0

        if (!mPhotoIds.isEmpty()) {
            final long ONE_MEGABYTE = 1024 * 1024;
            for (int i = 0; i < mPhotoIds.size(); i++) {

                StorageReference photoRef = mStorageIns.getReference().child("images/" + mPhotoIds.get(i) + ".png");

//                    final File localFile = File.createTempFile(mPhotoIds.get(i), "png"); // içine yüklenecek değişken
                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);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.i("SELFIEFRAGMENT", e.getMessage());

                    }
                });
            }
        }

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

        mLayoutManager = new GridLayoutManager(getActivity(), 2);
        mRecyclerView.setLayoutManager(mLayoutManager);
        mRecyclerView.setItemAnimator(new DefaultItemAnimator());

        Log.i("SELFIEFRAGMENT", "Array size is : " + mPhotoIds.size()); // PRINTS 0
        // PRINTS 0

        return view;
    }
}

Answer 1

您必须在onDataChange的for循环之后立即调用Firebase存储功能。

//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) {

                for (DataSnapshot uniqueKeySnapshot : dataSnapshot.getChildren()) {
                    String image_name = uniqueKeySnapshot.getValue(String.class);
                    Log.i("SELFIES", image_name); // PRINTING when everything is finished
                    mPhotoIds.add(image_name);
                }

          if (!mPhotoIds.isEmpty()) {
                final long ONE_MEGABYTE = 1024 * 1024;
                for (int i = 0; i < mPhotoIds.size(); i++) {

                StorageReference photoRef = mStorageIns.getReference().child("images/" + mPhotoIds.get(i) + ".png");

    //                    final File localFile = File.createTempFile(mPhotoIds.get(i), "png"); // içine yüklenecek değişken
                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);
                    }
                }).addOnFailureListener(new OnFailureListener() {
                    @Override
                    public void onFailure(@NonNull Exception e) {
                        Log.i("SELFIEFRAGMENT", e.getMessage());

                    }
                });
             }
         }

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

          mLayoutManager = new GridLayoutManager(getActivity(), 2);
          mRecyclerView.setLayoutManager(mLayoutManager);
          mRecyclerView.setItemAnimator(new DefaultItemAnimator());

         Log.i("SELFIEFRAGMENT", "Array size is : " + mPhotoIds.size()); // PRINTS 0

     }

     @Override
     public void onCancelled(@NonNull DatabaseError databaseError) {
           Log.i("SELFIEFRAGMENT", databaseError.getMessage());
     }
 });

Firebase在片段中从数据库获取值

1 个答案: