Java 在RecyclerView中未从Firebase获取数据

每个人，我都在尝试制作一个音乐应用程序，为此，我在我的

HomeFragment

中创建了一个水平

RecyclerView

，我的水平

RecyclerView

得到了一张有艺术家名字的图像

但单击后，我加载另一个活动。在我的另一项活动中，我试图使用

RecyclerView

从firebase在

列表视图中加载SongsData

但问题是我没有从Firebase获取数据，它返回的是空数据。我在下面提供了我的代码，这是我的Firebase数据库的屏幕截图：-

我的列表类：-

    public class TestUploads
    {
        private String songName;
        private String songImageUri;
        private String songUrl;
        private String artistName;

        public TestUploads() {
        }

        public String getSongName() {
            return songName;
        }

        public void setSongName(String SongName) {
            this.songName = SongName;
        }

        public String getSongImageUri() {
            return songImageUri;
        }

        public void setSongImageUri(String SongImageUri) {
            this.songImageUri = SongImageUri;
        }

        public String getSongUrl() {
            return songUrl;
        }

        public void setSongUrl(String SongUrl) {
            this.songUrl = songUrl;
        }

        public TestUploads(String SongImageUri, String SongName, String SongUrl ) {
            this.songName = SongName;
            this.artistName = SongImageUri;
            this.songUrl = SongUrl;

        }
    }


    public class TestAdapter extends RecyclerView.Adapter<TestAdapter.TestViewHolder>{

        private Context mContext;
        private List<TestUploads> mUploads;

        public TestAdapter(Context context , List<TestUploads> uploads) {
            mContext = context;
            mUploads = uploads;
        }

        @NonNull
        @Override
        public TestViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(mContext).inflate(R.layout.test_package_layout , parent ,false);
            return new TestViewHolder(v);
        }

        @Override
        public void onBindViewHolder(@NonNull TestViewHolder holder, int position) {


            TestUploads uploadcurrent = mUploads.get(position);

            holder.name.setText(uploadcurrent.getSongName());

            Glide.with(mContext)
                    .load(uploadcurrent.getSongImageUri())
                    .into(holder.image_view);

        }

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


        public class TestViewHolder extends RecyclerView.ViewHolder {

            public TextView name;
            public TextView artist_name;
            public CircleImageView image_view;

            public TestViewHolder(@NonNull View itemView) {
                super(itemView);

                name = itemView.findViewById(R.id.test_package_song_name);
                artist_name = itemView.findViewById(R.id.test_package_artist_name);
                image_view = itemView.findViewById(R.id.test_package_image_name);

            }
        }

    }

    public class TestActivity extends AppCompatActivity {

        private ValueEventListener listener;
        private DatabaseReference reference;
        private List<TestUploads> mUploads;

        private RecyclerView mRecyclerView;

        private TestAdapter adapter;


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

            reference = FirebaseDatabase.getInstance().getReference("ArtistView").child(getIntent().getStringExtra("Artist"))
            .child("Songs");

            Toast.makeText(this, "" + getIntent().getStringExtra("Artist"), Toast.LENGTH_SHORT).show();

            mUploads = new ArrayList<>();

            mRecyclerView = findViewById(R.id.test_pacakge_recyclerView);
            mRecyclerView.setHasFixedSize(true);
            mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
            mRecyclerView.smoothScrollToPosition(0);


            adapter = new TestAdapter(this , mUploads);

            mRecyclerView.setAdapter(adapter);

            listener = reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    mUploads.clear();

                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                        TestUploads uploads =postSnapshot.getValue(TestUploads.class);
                        mUploads.add(uploads);
                    }

                    adapter.notifyDataSetChanged();
                }

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

                }
            });
        }
    }


我的适配器类：-

    public class TestUploads
    {
        private String songName;
        private String songImageUri;
        private String songUrl;
        private String artistName;

        public TestUploads() {
        }

        public String getSongName() {
            return songName;
        }

        public void setSongName(String SongName) {
            this.songName = SongName;
        }

        public String getSongImageUri() {
            return songImageUri;
        }

        public void setSongImageUri(String SongImageUri) {
            this.songImageUri = SongImageUri;
        }

        public String getSongUrl() {
            return songUrl;
        }

        public void setSongUrl(String SongUrl) {
            this.songUrl = songUrl;
        }

        public TestUploads(String SongImageUri, String SongName, String SongUrl ) {
            this.songName = SongName;
            this.artistName = SongImageUri;
            this.songUrl = SongUrl;

        }
    }


    public class TestAdapter extends RecyclerView.Adapter<TestAdapter.TestViewHolder>{

        private Context mContext;
        private List<TestUploads> mUploads;

        public TestAdapter(Context context , List<TestUploads> uploads) {
            mContext = context;
            mUploads = uploads;
        }

        @NonNull
        @Override
        public TestViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(mContext).inflate(R.layout.test_package_layout , parent ,false);
            return new TestViewHolder(v);
        }

        @Override
        public void onBindViewHolder(@NonNull TestViewHolder holder, int position) {


            TestUploads uploadcurrent = mUploads.get(position);

            holder.name.setText(uploadcurrent.getSongName());

            Glide.with(mContext)
                    .load(uploadcurrent.getSongImageUri())
                    .into(holder.image_view);

        }

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


        public class TestViewHolder extends RecyclerView.ViewHolder {

            public TextView name;
            public TextView artist_name;
            public CircleImageView image_view;

            public TestViewHolder(@NonNull View itemView) {
                super(itemView);

                name = itemView.findViewById(R.id.test_package_song_name);
                artist_name = itemView.findViewById(R.id.test_package_artist_name);
                image_view = itemView.findViewById(R.id.test_package_image_name);

            }
        }

    }

    public class TestActivity extends AppCompatActivity {

        private ValueEventListener listener;
        private DatabaseReference reference;
        private List<TestUploads> mUploads;

        private RecyclerView mRecyclerView;

        private TestAdapter adapter;


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

            reference = FirebaseDatabase.getInstance().getReference("ArtistView").child(getIntent().getStringExtra("Artist"))
            .child("Songs");

            Toast.makeText(this, "" + getIntent().getStringExtra("Artist"), Toast.LENGTH_SHORT).show();

            mUploads = new ArrayList<>();

            mRecyclerView = findViewById(R.id.test_pacakge_recyclerView);
            mRecyclerView.setHasFixedSize(true);
            mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
            mRecyclerView.smoothScrollToPosition(0);


            adapter = new TestAdapter(this , mUploads);

            mRecyclerView.setAdapter(adapter);

            listener = reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    mUploads.clear();

                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                        TestUploads uploads =postSnapshot.getValue(TestUploads.class);
                        mUploads.add(uploads);
                    }

                    adapter.notifyDataSetChanged();
                }

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

                }
            });
        }
    }


公共类TestAdapter扩展了RecyclerView.Adapter{
私有上下文；
私人列表多路复用器；
公共测试适配器（上下文、列表上载）{
mContext=上下文；
mUploads=上传；
}
@非空
@凌驾
公共TestViewHolder onCreateViewHolder（@NonNull ViewGroup父级，int-viewType）{
视图v=LayoutFlater.from（mContext）。充气（R.layout.test\u package\u布局，父级，false）；
返回新的TestViewHolder（v）；
}
@凌驾
public void onBindViewHolder（@NonNull TestViewHolder，int位置）{
TestUploads uploadcurrent=mUploads.get（位置）；
holder.name.setText（uploadcurrent.getSongName（））；
使用（mContext）滑动
.load（uploadcurrent.getSongImageUri（））
.进入（支架图像视图）；
}
@凌驾
public int getItemCount（）{
回传多倍体
.size（）；
}
公共类TestViewHolder扩展了RecyclerView.ViewHolder{
公共文本视图名称；
公共文本视图艺术家名称；
公共环路图像视图图像视图；
公共TestViewHolder（@NonNull View itemView）{
超级（项目视图）；
name=itemView.findviewbyd（R.id.test\u package\u song\u name）；
艺术家名称=itemView.findViewById（R.id.test\u package\u艺术家名称）；
image\u view=itemView.findviewbyd（R.id.test\u package\u image\u name）；
}
}
}

我的活动：-

    public class TestUploads
    {
        private String songName;
        private String songImageUri;
        private String songUrl;
        private String artistName;

        public TestUploads() {
        }

        public String getSongName() {
            return songName;
        }

        public void setSongName(String SongName) {
            this.songName = SongName;
        }

        public String getSongImageUri() {
            return songImageUri;
        }

        public void setSongImageUri(String SongImageUri) {
            this.songImageUri = SongImageUri;
        }

        public String getSongUrl() {
            return songUrl;
        }

        public void setSongUrl(String SongUrl) {
            this.songUrl = songUrl;
        }

        public TestUploads(String SongImageUri, String SongName, String SongUrl ) {
            this.songName = SongName;
            this.artistName = SongImageUri;
            this.songUrl = SongUrl;

        }
    }


    public class TestAdapter extends RecyclerView.Adapter<TestAdapter.TestViewHolder>{

        private Context mContext;
        private List<TestUploads> mUploads;

        public TestAdapter(Context context , List<TestUploads> uploads) {
            mContext = context;
            mUploads = uploads;
        }

        @NonNull
        @Override
        public TestViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
            View v = LayoutInflater.from(mContext).inflate(R.layout.test_package_layout , parent ,false);
            return new TestViewHolder(v);
        }

        @Override
        public void onBindViewHolder(@NonNull TestViewHolder holder, int position) {


            TestUploads uploadcurrent = mUploads.get(position);

            holder.name.setText(uploadcurrent.getSongName());

            Glide.with(mContext)
                    .load(uploadcurrent.getSongImageUri())
                    .into(holder.image_view);

        }

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


        public class TestViewHolder extends RecyclerView.ViewHolder {

            public TextView name;
            public TextView artist_name;
            public CircleImageView image_view;

            public TestViewHolder(@NonNull View itemView) {
                super(itemView);

                name = itemView.findViewById(R.id.test_package_song_name);
                artist_name = itemView.findViewById(R.id.test_package_artist_name);
                image_view = itemView.findViewById(R.id.test_package_image_name);

            }
        }

    }

    public class TestActivity extends AppCompatActivity {

        private ValueEventListener listener;
        private DatabaseReference reference;
        private List<TestUploads> mUploads;

        private RecyclerView mRecyclerView;

        private TestAdapter adapter;


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

            reference = FirebaseDatabase.getInstance().getReference("ArtistView").child(getIntent().getStringExtra("Artist"))
            .child("Songs");

            Toast.makeText(this, "" + getIntent().getStringExtra("Artist"), Toast.LENGTH_SHORT).show();

            mUploads = new ArrayList<>();

            mRecyclerView = findViewById(R.id.test_pacakge_recyclerView);
            mRecyclerView.setHasFixedSize(true);
            mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
            mRecyclerView.smoothScrollToPosition(0);


            adapter = new TestAdapter(this , mUploads);

            mRecyclerView.setAdapter(adapter);

            listener = reference.addValueEventListener(new ValueEventListener() {
                @Override
                public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                    mUploads.clear();

                    for (DataSnapshot postSnapshot : dataSnapshot.getChildren()) {
                        TestUploads uploads =postSnapshot.getValue(TestUploads.class);
                        mUploads.add(uploads);
                    }

                    adapter.notifyDataSetChanged();
                }

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

                }
            });
        }
    }


公共类测试活动扩展了AppCompative活动{
私人价值观；
私人数据库参考；
私人列表多路复用器；
私人回收视图mRecyclerView；
专用测试适配器；
@凌驾
创建时受保护的void（@Nullable Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.test\u package\u活动）；
reference=FirebaseDatabase.getInstance（）.getReference（“ArtistView”）.child（getIntent（）.getStringExtra（“艺术家”））
.儿童（“歌曲”）；
Toast.makeText（this，“+getIntent（）.getStringExtra（“艺术家”），Toast.LENGTH_SHORT.show（）；
mUploads=newarraylist（）；
mRecyclerView=findViewById（R.id.test\u pacakge\u recyclerView）；
mRecyclerView.setHasFixedSize（true）；
mRecyclerView.setLayoutManager（新的LinearLayoutManager（this））；
mRecyclerView.smoothScrollToPosition（0）；
适配器=新约适配器（此为多端口）；
mRecyclerView.setAdapter（适配器）；
listener=reference.addValueEventListener（新的ValueEventListener（）{
@凌驾
public void onDataChange（@NonNull DataSnapshot DataSnapshot）{
mUploads.clear（）；
对于（DataSnapshot postSnapshot:DataSnapshot.getChildren（））{
TestUploads uploads=postSnapshot.getValue（TestUploads.class）；
添加（上传）；
}
adapter.notifyDataSetChanged（）；
}
@凌驾
已取消的公共void（@NonNull DatabaseError DatabaseError）{
}
});
}
}

很抱歉有这么多代码，但这并不难解决。如果你找到了解决办法，请回复我。感谢阅读。
代码中的问题在于
TestUploads
类中字段的名称与数据库中属性的名称不同。您的
TestUploads
类中有一个名为
songName
的字段，但在您的数据库中，我看到它是
songName
，这是不正确的。名称必须匹配。当您使用名为
getSongName（）
的getter时，Firebase正在数据库中查找名为
songName
和非
songName
的字段。请参见小写字母
s
与大写字母
s

有两种方法可以解决这个问题。第一种方法是删除数据库中的数据，然后使用以小写字母开头的字段名再次添加数据，就像
TestUploads
类中存在的那样

如果不允许您使用第一种解决方案，那么第二种方法将是使用
注释
。因此，您应该在getter前面使用注释。因此，在您的
TestUploads
类中，getter应该如下所示：

@PropertyName("SongName")
public String getSongName() {
    return songName;
}

代码中的问题在于
TestUploads
类中字段的名称与数据库中属性的名称不同。您的
TestUploads
类中有一个名为
songName
的字段，但在您的数据库中，我看到它是
songName
，这是不正确的。名称必须匹配。当您使用名为
getSongName（）
的getter时，Firebase正在数据库中查找名为
songName
和非
songName
的字段。请参见小写的
s