无法在RecyclerView中显示从Firebase检索的数据

Question

我相信我的recyclerView已成功从firebase检索数据，因为它在我的recycler视图中显示了2个cardView，这与我在Firebase中的Menu下分配的数据数量相同。

“ >>

Screenshot of my RecyclerView。

我有3个类，分别是listOnline2，MyAdapter和cMenu。 lisOnline2和MyAdapter中都有一个数组。我在listOnline2中使用数组来存储从firebase检索到的数据，并在MyAdapter中使用数组来查看cardview中的数据。下面是我对类listOnline2的编码。

`DatabaseReference currentUserRef,counterRef, ref;
MyAdapter adapterR;

RecyclerView listOnline21;
ArrayList <cMenu> menu;
private static final String TAG = "listOnline2";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_list_online2 );

    listOnline21= (RecyclerView) findViewById(R.id.listMenu);
    listOnline21.setLayoutManager( new LinearLayoutManager( listOnline2.this ) );
    listOnline21.setHasFixedSize(true);
menu= new ArrayList<cMenu>();


    counterRef= FirebaseDatabase.getInstance().getReference().child( "Menu" ).child( "twRAlXRMSgPkA35nmMoFAuAsTdz1" );
    Log.d( TAG, "Clicked ID: "+idd );
    currentUserRef=FirebaseDatabase.getInstance().getReference("Menu").child( FirebaseAuth.getInstance().getCurrentUser().getUid() );

    counterRef.addValueEventListener( new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            for(DataSnapshot dataSnapshot1: dataSnapshot.getChildren()){

                cMenu p=dataSnapshot1.getValue(cMenu.class);
                menu.add(p);

            }
            Log.d( TAG, "Data of array: "+menu );
            adapterR=new MyAdapter( listOnline2.this, menu );
            listOnline21.setAdapter( adapterR );
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(listOnline2.this, "Opsss.... Something is wrong", Toast.LENGTH_SHORT).show();
        }
    } );

    Toolbar toolbar=findViewById(R.id.toolbar);
    toolbar.setTitle("Food Ordering Delivery System");
    setSupportActionBar(toolbar);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater= getMenuInflater();
    inflater.inflate( R.menu.main_menu,menu );
    return true;
}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()){
        case R.id.action_cart:
            Intent toCart=new Intent( listOnline2.this, Cart.class );
            startActivity( toCart );
            break;

        case R.id.action_logout:
            Intent toLogin=new Intent( listOnline2.this, LoginActivity.class );
            startActivity( toLogin );

            break;
    }
    return super.onOptionsItemSelected( item );
}`
同时，以下是我在MyAdapter类中的代码

DatabaseReference currentUserRef,counterRef;
MyAdapter adapterR;

RecyclerView listOnline21;
ArrayList <cMenu> menu;
private static final String TAG = "listOnline2";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate( savedInstanceState );
    setContentView( R.layout.activity_list_online2 );

    listOnline21= (RecyclerView) findViewById(R.id.listMenu);
    listOnline21.setLayoutManager( new LinearLayoutManager( listOnline2.this ) );
    listOnline21.setHasFixedSize(true);
       menu= new ArrayList<cMenu>();


    counterRef= FirebaseDatabase.getInstance().getReference().child( "Menu" ).child( "twRAlXRMSgPkA35nmMoFAuAsTdz1" );
    Log.d( TAG, "Clicked ID: "+idd );
    currentUserRef=FirebaseDatabase.getInstance().getReference("Menu").child( FirebaseAuth.getInstance().getCurrentUser().getUid() );

    counterRef.addValueEventListener( new ValueEventListener() {
        @Override
        public void onDataChange(@NonNull DataSnapshot dataSnapshot) {

            for(DataSnapshot dataSnapshot1: dataSnapshot.getChildren()){

                cMenu p=dataSnapshot1.getValue(cMenu.class);
                menu.add(p);

            }
            Log.d( TAG, "Data of array: "+menu );
            adapterR=new MyAdapter( listOnline2.this, menu );
            listOnline21.setAdapter( adapterR );
        }

        @Override
        public void onCancelled(@NonNull DatabaseError databaseError) {
            Toast.makeText(listOnline2.this, "Opsss.... Something is wrong", Toast.LENGTH_SHORT).show();
        }
    } );

    Toolbar toolbar=findViewById(R.id.toolbar);
    toolbar.setTitle("Food Ordering Delivery System");
    setSupportActionBar(toolbar);
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    MenuInflater inflater= getMenuInflater();
    inflater.inflate( R.menu.main_menu,menu );
    return true;
}

@Override
public boolean onOptionsItemSelected(@NonNull MenuItem item) {
    switch (item.getItemId()){
        case R.id.action_cart:
            Intent toCart=new Intent( listOnline2.this, Cart.class );
            startActivity( toCart );
            break;

        case R.id.action_logout:
            Intent toLogin=new Intent( listOnline2.this, LoginActivity.class );
            startActivity( toLogin );

            break;
    }
    return super.onOptionsItemSelected( item );
}
最后一个类是cMenu，如下所示：

private String fName, fDesc, fImage, fQuantity, fPrice, fId;

public cMenu() {
}

public cMenu(String fName, String fDesc, String fImage, String fQuantity, String fPrice, String fId) {
    this.fName = fName;
    this.fDesc = fDesc;
    this.fImage = fImage;
    this.fQuantity = fQuantity;
    this.fPrice = fPrice;
    this.fId = fId;
}

public String getfName() {
    return fName;
}

public void setfName(String fName) {
    this.fName = fName;
}

public String getfDesc() {
    return fDesc;
}

public void setfDesc(String fDesc) {
    this.fDesc = fDesc;
}

public String getfImage() {
    return fImage;
}

public void setfImage(String fImage) {
    this.fImage = fImage;
}

public String getfQuantity() {
    return fQuantity;
}

public void setfQuantity(String fQuantity) {
    this.fQuantity = fQuantity;
}

public String getfPrice() {
    return fPrice;
}

public void setfPrice(String fPrice) {
    this.fPrice = fPrice;
}

public String getfId() {
    return fId;
}

public void setfId(String fId) {
    this.fId = fId;
}
如何显示存储从Firebase检索到的数据的阵列中的数据？请给我一个建议，因为我花了2天时间看这些规范。预先谢谢！

我相信我的recyclerView已成功从firebase检索数据，因为它在recycler视图中显示了2个cardView，这与我在Firebase中的Menu下分配的数据数量相同。 ...

Answer 1

int id = FirebaseAuth.getInstance.getCurrentUser.getUid（）;currentUserRef = FirebaseDatabase.getInstance（）。getReference（）。child（“ Menu”）。child（id）;