无法正确将 Firebase 数据导入 RecyclerView（Android）

Question

我在将数据从 Firebase 数据库导入应用程序的 RecyclerView 时遇到问题。我想从 UserUid 子项中获取数据到单独的 CardViews 中，但我只得到一个 CardView 与数据库中的最后一个数据子项。我在 YouTube 上看过 tutorial，但没有任何关于使用 dataSnapshot 获取数据的信息。我想我应该使用 Array 来获取数据，因为我在Log 中得到了所有的data，但不知道该怎么做。请帮忙解释一下。 先谢谢了。

ViewDatabase.class

package com.mcarrow.mapsservicerunning;

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.text.TextUtils;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;
import android.widget.Toast;

import com.firebase.ui.database.FirebaseRecyclerAdapter;
import com.google.firebase.auth.FirebaseAuth;
import com.google.firebase.auth.FirebaseUser;
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 java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.List;

public class ViewDatabase extends AppCompatActivity {
private static final String TAG="ViewDatabase";
private FirebaseDatabase mFirebaseDatabase;
private FirebaseAuth mAuth;
private FirebaseAuth.AuthStateListener mAuthListener;
private DatabaseReference myRef;
private RecyclerView mBlogList;
private String userID;
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view_database_layout);
    mAuth=FirebaseAuth.getInstance();
    mFirebaseDatabase= FirebaseDatabase.getInstance();
    myRef=mFirebaseDatabase.getReference("users");
    myRef.keepSynced(true);
    mBlogList=(RecyclerView)findViewById(R.id.myrecycleview);
    mBlogList.setHasFixedSize(true);
    mBlogList.setLayoutManager(new LinearLayoutManager(this));
    FirebaseUser user=mAuth.getInstance().getCurrentUser();
    userID=user.getUid();
    mAuthListener=new FirebaseAuth.AuthStateListener() {
        @Override
        public void onAuthStateChanged(@NonNull FirebaseAuth firebaseAuth) {
            FirebaseUser user =firebaseAuth.getInstance().getCurrentUser();
            if(user!=null){
                Log.d(TAG,"Signed in"+user.getUid());
                toastMessage("Signed In"+user.getEmail());
            }else {
                Log.d(TAG,"Signed Out");
                toastMessage("Signed Out");
            }

        }
    };
    myRef.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
            showData(dataSnapshot);

        }

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

        }
    });
}

private void showData(DataSnapshot dataSnapshot) {
    final DataSnapshot contactSnapshot=dataSnapshot.child(userID);




        final FirebaseRecyclerAdapter<UserInformation, BlogViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<UserInformation, BlogViewHolder>(UserInformation.class, R.layout.blog_row, BlogViewHolder.class, myRef) {
            @Override
            protected void populateViewHolder(BlogViewHolder viewHolder, UserInformation model, int position) {
                Iterable<DataSnapshot>contactChildren=contactSnapshot.getChildren();
                for (DataSnapshot contact : contactChildren) {
                UserInformation uInfo = new UserInformation();
                uInfo.setTitle(contact.getValue(UserInformation.class).getTitle());
                    uInfo.setDesc(contact.getValue(UserInformation.class).getDesc());
                viewHolder.setTitle(uInfo.getTitle());
                Log.d(TAG, "viewHolder " + uInfo.getTitle());
                viewHolder.setDesc(uInfo.getDesc());

            }
        }

    };
    mBlogList.setAdapter(firebaseRecyclerAdapter);
}

    public static class BlogViewHolder extends RecyclerView.ViewHolder{
    View mView;
    public BlogViewHolder(View itemView){
        super(itemView);
        mView=itemView;
    }
    public void setTitle(double title){
        TextView post_title=(TextView)mView.findViewById(R.id.post_title);
        post_title.setText(""+title);
    }
        public void setDesc(String desc){
            TextView post_desc=(TextView)mView.findViewById(R.id.post_desc);
            post_desc.setText(desc);
        }
    }


@Override
protected void onStart() {
    super.onStart();
    mAuth.addAuthStateListener(mAuthListener);

}

@Override
protected void onStop() {
    super.onStop();
    if(mAuthListener!=null){
        mAuth.removeAuthStateListener(mAuthListener);
    }
}
private void toastMessage(String message){
    Toast.makeText(this,message,Toast.LENGTH_SHORT).show();
}
}

UserInformation.class

package com.mcarrow.mapsservicerunning;

public class UserInformation {
private double title;
private String desc;

public UserInformation(double title, String desc) {
    this.title = title;
    this.desc = desc;
}

public double getTitle() {
    return title;
}

public void setTitle(double title) {
    this.title = title;
}

public String getDesc() {
    return desc;
}

public void setDesc(String desc) {
    this.desc = desc;
}

public UserInformation(){

}
}

Answer 1

您应该在 Activity 的 onCreate 方法中设置适配器。您还应该创建一个自定义适配器来根据需要显示项目。

你的活动课：

RecyclerView studyGroupsRV;
LayoutManager layoutManager;
...

@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.view_database_layout);

    // declare view variables ...
    studyGroupsRV = context.findViewById(R.id.studyGroupsRV);

    dbStudyGroups = FirebaseDatabase.getInstance().getReference().child("studyGroups");
    // Set the event listener:
    dbStudyGroups.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
            // This will be called as many times as many items have you 
            studyGroupsAdapter.addStudyGroup(new StudyGroup(
                    dataSnapshot.getKey(),                        
                    dataSnapshot.child("title").getValue().toString(),
                    dataSnapshot.child("description").getValue().toString(),
                    dataSnapshot.child("age").getValue().toString(),
                    dataSnapshot.child("room").getValue().toString(),
                    dataSnapshot.child("time").getValue().toString()
            ));
        }

        @Override
        public void onChildChanged(@NonNull DataSnapshot dataSnapshot, @Nullable String s) {
            // You can handle here the item changes
        }

        // Removes the deleted item from the adapter's dataset
        @Override
        public void onChildRemoved(@NonNull DataSnapshot dataSnapshot) {
            studyGroupsAdapter.removeStudyGroupByKey(dataSnapshot.getKey());
        }

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

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            // You can handle here the errors
        }
    });

    StudyGroupsAdapter studyGroupsAdapter = new StudyGroupsAdapter(this, new ArrayList<>());
    layoutManager = new LinearLayoutManager(this);
    studyGroupsRV.setAdapter(studyGroupsAdapter);
    studyGroupsRV.setLayoutManager(layoutManager);
    studyGroupsRV.setItemAnimator(new DefaultItemAnimator());

然后你就可以创建自己的Adapter类了：

import android.content.Context;
import android.content.Intent;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.TextView;

import java.util.ArrayList;

public class StudyGroupsAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder> {

    public static final int TYPE_STUDY_GROUP = 1;
    private static final int TYPE_HEADER = 0;
    private static ArrayList<StudyGroup> studyGroups;


    private Context context;
    private LayoutInflater inflater;

    private Holder<Boolean> isOpenedPost;


    /**
     * Constructor
     *
     * @param context
     * @param studyGroups
     */
    public StudyGroupsAdapter(Context context, ArrayList<StudyGroup> studyGroups) {
        this.context = context;
        this.studyGroups = studyGroups;
        inflater = LayoutInflater.from(context);
        isOpenedPost = new Holder<>(false);

    }

    /**
     * Gets the data list
     */
    public static ArrayList<StudyGroup> getStudyGroups() {
        return studyGroups;
    }

    /** Set the dataset */
    public void setStudyGroups(ArrayList<StudyGroup> studyGroups) {
        this.studyGroups = studyGroups;
        notifyDataSetChanged();
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        // You can create multiple types of views
        return new StudyGroupHolder(inflater.inflate(R.layout.study_group_row, parent, false));

    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder_, int position) {
            StudyGroupHolder holder = (StudyGroupHolder) holder_;

            holder.title.setText(studyGroups.get(position).getTitle());
             holder.excerpt.setText(studyGroups.get(position).getDescription());
            holder.time.setText(studyGroups.get(position).getTime());



        }

    }

    /**
     * Get the size of the RecyclerView List
     *
     * @return the size of the list
     */
    @Override
    public int getItemCount() {
        return studyGroups.size();
    }

    // You can add an item to the list by this method (in firebase onChildAdded event)
    public void addStudyGroup(StudyGroup studyGroup) {
        studyGroups.add(studyGroup);
        notifyDataSetChanged();
    }

    // It removes all the items from the dataset (and the list)
    public void removeStudyGroups() {
        studyGroups.clear();
        notifyDataSetChanged();
    }

    // Removes an item by friebase key (You can call it from firebase onChildRemoved event)
    public void removeStudyGroupByKey(String key) {
        for (int i = 0; i < studyGroups.size(); i++) {
            if (studyGroups.get(i).getKey().equals(key)) {
                studyGroups.remove(i);
            }
        }
        notifyDataSetChanged();
    }

    private class StudyGroupHolder extends RecyclerView.ViewHolder {
        TextView title;
        TextView excerpt;
        TextView time;
        Button readMoreButton;

        public StudyGroupHolder(View itemView) {
            super(itemView);
            title = itemView.findViewById(R.id.studyGroupTitle);
            excerpt = itemView.findViewById(R.id.studyGroupDescription);
            time = itemView.findViewById(R.id.studyGroupTime);
            readMoreButton = itemView.findViewById(R.id.SGreadMoreBtn);
        }
    }
}