FirebaseUI 填充 ListView 文本不显示

Question

我正在使用 Firebase 数据库和 Firebase-UI 填充 ListView 首歌曲，所有依赖项都已正确初始化并且应用已与数据库连接，但是当它显示列表时却没有' 显示文本，只是像这样的空框：

将项目添加到数据库后，会添加一个框，但不显示文本。这是代码：

歌曲class:

package com.example.gloriadesideri.animas;

public class Song
{
    private String myName;
    private String myURL;
    private String myAuthor;

    public Song(){
        /*myName="";
        myURL="";
        myAuthor="";*/
    }

    public Song(String Author, String Song, String URL) {
        this.myName=Song;
        this.myURL=URL;
        this.myAuthor=Author;
    }
    public String getName()
    {
        return myName;
    }
    public String getURL()
    {
        return myURL;
    }
    public String getAuthor()
    {
        return myAuthor;
    }
    public void setName(String name)
    {
        this.myName=name;
    }
    public void setURL ( String URL)
    {
        this.myURL=URL;
    }
    public void setAuthor(String author)
    {
        this.myAuthor=author;
    }
}

歌曲布局：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical"
    android:layout_margin="20dp"
    android:padding="10dp">

    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/songName"/>
    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/author"/>
</LinearLayout>

Activity 应该有列表视图：

package com.example.gloriadesideri.animas;

import android.content.Intent;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBar;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.TextView;

import com.firebase.ui.database.FirebaseListAdapter;
import com.firebase.ui.database.FirebaseListOptions;
import com.google.firebase.database.ChildEventListener;
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.Query;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;
import java.util.List;

public class Canzoni extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener
{
   //nav view parameters
    private DrawerLayout cDrawerLayout;
    private ActionBarDrawerToggle cToggle;

    //list view parameters
    private ListView mListView;

    //firebase parameters
     private FirebaseListAdapter mAdapter;

    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_canzoni);
        //nav view code
        cDrawerLayout= (DrawerLayout) findViewById(R.id.draw_viewC);
        cToggle= new ActionBarDrawerToggle(this, cDrawerLayout,R.string.Open, R.string.Close);
        cDrawerLayout.addDrawerListener(cToggle);
        cToggle.syncState();


        ActionBar actionBar = getSupportActionBar();
        if (actionBar != null)
            actionBar.setDisplayHomeAsUpEnabled(true);
        NavigationView cNavigationView = (NavigationView) findViewById(R.id.nav_viewC);
        if (cNavigationView != null)
        {
            cNavigationView.setNavigationItemSelectedListener(this);
        }

        Query mQuery= FirebaseDatabase.getInstance().getReference().child("songs");
        mListView= (ListView) findViewById(R.id.canzoni_list);
        FirebaseListOptions<Song>  mOptions= new FirebaseListOptions.Builder<Song>()
                .setLayout(R.layout.song_layout)
                .setQuery(mQuery, Song.class)
                .setLifecycleOwner(this)
                .build();

        mAdapter= new FirebaseListAdapter <Song>(mOptions){
            @Override
            protected void populateView(View v, Song model, int position) {
                TextView songName= v.findViewById(R.id.songName);
                TextView songAuthor=v.findViewById(R.id.author);


                songName.setText(model.getName());
                songAuthor.setText(model.getAuthor());
            }
        };
        mListView.setAdapter(mAdapter);

        }

    @Override
    protected void onStart() {
        super.onStart();
        mAdapter.startListening();
    }

    @Override
    protected void onStop() {
        super.onStop();
        mAdapter.stopListening();
    }

    @Override

    public boolean onOptionsItemSelected(MenuItem Item)
    {
        if(cToggle.onOptionsItemSelected(Item))
        {
            return true;
        }
        return super.onOptionsItemSelected(Item);
    }
    @Override
    public boolean onNavigationItemSelected(MenuItem Item)
    {
        int id = Item.getItemId();
        Intent intent;
        if (id == R.id.preghiere)
        {
            intent= new Intent(this, Preghiere.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        else if ( id== R.id.bans)
        {
            intent= new Intent(this, Bans.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        else if (id== R.id.canzoni)
        {
            intent= new Intent(this, this.getClass());
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        else if (id==R.id.calendario)
        {
            intent= new Intent(this, Calendario.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        else if (id== R.id.per_riflettere)
        {
            intent= new Intent(this, perRiflettere.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        else if( id== R.id.home)
        {
            intent= new Intent(this, MainActivity.class);
            intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
            this.startActivity(intent);
        }
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.draw_viewC);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }

}

上面的布局activity

<android.support.v4.widget.DrawerLayout 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:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".Canzoni"
    android:id="@+id/draw_viewC">


    <ListView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/canzoni_list">

    </ListView>

    <android.support.design.widget.NavigationView
        android:layout_width="239dp"
        android:layout_height="match_parent"
        android:layout_gravity="start"
        android:background="@color/white"
        android:fitsSystemWindows="true"
        app:headerLayout="@layout/header"
        app:itemIconTint="@color/black"
        app:itemTextColor="@color/black"
        app:menu="@menu/drawem_menu"
        tools:layout_editor_absoluteX="0dp"
        tools:layout_editor_absoluteY="0dp"
        tools:ignore="MissingConstraints"
        android:id="@+id/nav_viewC"/>

</android.support.v4.widget.DrawerLayout>

关于如何解决这个问题有什么建议吗？

编辑:
数据库如下所示：

书写和阅读规则都正确

编辑

我已经更改了歌曲中的私有名称class，因此它们与数据库相同。

private String Author;

private String Song;

private String Url;

它开始工作了，问题是现在它只显示作者

Update 2

Answer 1

我这段代码从 firebase 获取用户数据并将数据显示到回收视图中。

在布局中我使用了约束布局你可以改变它..

display_data.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="match_parent">

<android.support.v7.widget.RecyclerView
    android:id="@+id/rvData"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

</android.support.v7.widget.RecyclerView>

<TextView
    android:id="@+id/dlTvEmpty"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="No Found"
    android:textSize="16dp"
    android:visibility="gone"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:layout_constraintTop_toTopOf="parent" />
 </android.support.constraint.ConstraintLayout>

然后在 row_layout 绑定到回收站视图后..

row_layout.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:padding="10dp">

<TextView
    android:id="@+id/rlTvName"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Name"
    android:textSize="20dp" />

<TextView
    android:id="@+id/rlTvEmail"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Email"
    android:textSize="20dp"
    app:layout_constraintTop_toBottomOf="@+id/rlTvName" />

<TextView
    android:id="@+id/rlTvPwd"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="Password"
    android:textSize="20dp"
    app:layout_constraintTop_toBottomOf="@+id/rlTvEmail" />


 </android.support.constraint.ConstraintLayout>

然后为插入 firebase 的用户制作 pojo class..

User.java

public class User {

public String name;
public String email;
public String pwd;
// Default constructor required for calls to
// DataSnapshot.getValue(User.class)
public User() {
}

public User(String name, String email,String pwd) {
    this.name = name;
    this.email = email;
    this.pwd=pwd;
}

}

然后在制作适配器后 class。

DisplayAllData.java

public class DisplayAllData extends RecyclerView.Adapter<DisplayAllData.ItemViewHolder> {
private List<User> mUserLsit = new ArrayList<>();
private Context mContext;

@Override
public ItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.row_layout, parent, false);
    return new ItemViewHolder(view);
}

public DisplayAllData(Context mContext, List<User> mUserLsit) {
    this.mContext = mContext;
    this.mUserLsit = mUserLsit;
}

@Override
public void onBindViewHolder(ItemViewHolder holder, int position) {
    User user = mUserLsit.get(position);
    holder.mTvName.setText(user.name);
    holder.mTvEmail.setText(user.email);
    holder.mTvPwd.setText(user.pwd);
}

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

public class ItemViewHolder extends RecyclerView.ViewHolder {
    TextView mTvName, mTvEmail, mTvPwd;

    public ItemViewHolder(View itemView) {
        super(itemView);
        mTvEmail = itemView.findViewById(R.id.rlTvEmail);
        mTvName = itemView.findViewById(R.id.rlTvName);
        mTvPwd = itemView.findViewById(R.id.rlTvPwd);

    }
}

}

然后最终显示 class 从 firebase 获取用户记录并绑定到 recyclerview。

DisplayActivity.java

public class DisplayActivity extends AppCompatActivity {
private RecyclerView mRvData;
private DisplayAllData allDataAdapter;
private DatabaseReference mDatabase;
private TextView mTvEmpty;
private FirebaseDatabase mFirebaseInstance;
private List<User> mUserList = new ArrayList<>();

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

private void initView() {
    mFirebaseInstance = FirebaseDatabase.getInstance();
    mDatabase = mFirebaseInstance.getReference("usersDb/UserTable");
    mRvData = findViewById(R.id.rvData);
    mTvEmpty = findViewById(R.id.dlTvEmpty);
    mRvData.setLayoutManager(new LinearLayoutManager(this));
    mDatabase.addValueEventListener(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            mUserList.clear();
            for (DataSnapshot dataSnapshot1 : dataSnapshot.getChildren()) {
                User user = dataSnapshot1.getValue(User.class);
                mUserList.add(user);
            }
            allDataAdapter = new DisplayAllData(DisplayActivity.this, mUserList);
            mRvData.setAdapter(allDataAdapter);
            allDataAdapter.notifyDataSetChanged();
            if (mUserList.isEmpty())
                mTvEmpty.setVisibility(View.VISIBLE);
            else
                mTvEmpty.setVisibility(View.GONE);
        }


        @Override
        public void onCancelled(DatabaseError databaseError) {

        }
    });
}

}

Answer 2

在您的数据库中，在名为 myAuthor 的歌曲名称下有一个属性，但在模型 class 中，您有一个名为 Author 的字段，两者应该相同。

要解决这个问题，您有两个解决方案。第一个是从您的数据库中删除所有记录并根据您的模型添加新数据 class。确保使用模型中存在的字段名称添加数据库中的属性 class：myName、myURL、myAuthor 和 NOT Author, Song, Url.

如果您未处于测试模式，则只需在您的模型中使用注释 class，如下所示：

@PropertyName("Song")
private String myName;
@PropertyName("Url")
private String myURL;
@PropertyName("Author")
private String myAuthor;

根据您编辑的问题，您提交的内容不正确。请问你 Song class 应该是什么样子：

public class Song {
    private String author, song, url;

    public Song() {}

    public Song(String author, String song, String url) {
        this.author = author;
        this.song = song;
        this.url = url;
    }

    public String getAuthor() { return author; }
    public String getSong() { return song; }
    public String getUrl() { return url; }
}

看到字段了吗？以首字母小写命名。

Answer 3

经过几次实验后更改此代码

songName.setText(model.getName());
songAuthor.setText(model.getAuthor());

至此

songName.setText(model.getURL());
    songAuthor.setText(model.getAuthor());

我了解到问题实际上出在我给 privates 的名称和我给 Song class 中的 get-methods 的名称。 privates 的名称应该与数据库字段相同，方法的名称应该是 getYourPrivateName()。

FirebaseUI 填充 ListView 文本不显示

FirebaseUI populate ListView text not displayed

java

android

firebase

firebase-realtime-database

firebaseui