即使設定了getitemcount并設定了layoutmanager，RecyclerView也不顯示任何專案-有解無憂

我嘗試了這里提到的大多數有類似問題的解決方案，但似乎沒有一個對我有用......現在我觀察到的是代碼能夠從 firebase 獲取資料并且它能夠設定資料但是getitemcount 方法沒有更新，即使在我將其設定為專案串列大小后，它仍然顯示為零，任何關于我做錯了什么的幫助都會有所幫助

Activity class

package com.example.sololeveling;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import android.os.Bundle;
import android.widget.Toast;

import com.example.sololeveling.DAO.CasinoCouponsDao;
import com.example.sololeveling.DAO.CasinoHistoryDao;
import com.example.sololeveling.DAO.CouponDao;
import com.example.sololeveling.DAO.UserDAO;
import com.example.sololeveling.Entity.CasinoHistory;
import com.example.sololeveling.adapter.CasinoHistoryAdapter;
import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.ValueEventListener;

import java.util.ArrayList;

public class HistoryActivity extends AppCompatActivity {

    CasinoHistoryDao casinoHistoryDao;
    RecyclerView casinoHistoryView;
    CasinoHistoryAdapter casinoHistoryAdapter;

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

        initializeLevelObjects();
        loadRollHistory();


        casinoHistoryView.setAdapter(casinoHistoryAdapter);
        casinoHistoryView.setLayoutManager(new LinearLayoutManager(this));
    }

    private void loadRollHistory()
    {
        casinoHistoryDao.get().addValueEventListener(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot snapshot) {
                ArrayList<CasinoHistory> casinoHistoryArrayList = new ArrayList<>();
                for(DataSnapshot dataSnapshot : snapshot.getChildren())
                {
                    CasinoHistory casinoHistory = dataSnapshot.getValue(CasinoHistory.class);
                    casinoHistory.setKey(dataSnapshot.getKey());
                    casinoHistoryArrayList.add(casinoHistory);
                }
                casinoHistoryAdapter.setCasinoHistoryArrayList(casinoHistoryArrayList);
            }

            @Override
            public void onCancelled(@NonNull DatabaseError error) {
                Toast.makeText(HistoryActivity.this, "Fail to get data.", Toast.LENGTH_SHORT).show();
            }
        });
    }

    private void initializeLevelObjects()
    {
        casinoHistoryDao = new CasinoHistoryDao();
        casinoHistoryView = findViewById(R.id.historyrollview);
        casinoHistoryAdapter = new CasinoHistoryAdapter(this);
    }
}

Adapter class

package com.example.sololeveling.adapter;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.example.sololeveling.Entity.CasinoHistory;
import com.example.sololeveling.R;
import com.example.sololeveling.ViewHolder.CasinoHistoryViewHolder;

import java.util.ArrayList;

public class CasinoHistoryAdapter extends RecyclerView.Adapter<RecyclerView.ViewHolder>
{
    private Context context;
    ArrayList<CasinoHistory> casinoHistoryArrayList = new ArrayList<>();

    public CasinoHistoryAdapter(Context context) {
        this.context = context;
    }

    public void setCasinoHistoryArrayList(ArrayList<CasinoHistory> casinoHistories)
    {
        this.casinoHistoryArrayList = casinoHistories;
    }

    @NonNull
    @Override
    public RecyclerView.ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(context).inflate(R.layout.casino_history_list, parent, false);
        return new CasinoHistoryViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull RecyclerView.ViewHolder holder, int position) {
        CasinoHistoryViewHolder casinoHistoryViewHolder = (CasinoHistoryViewHolder) holder;
        CasinoHistory casinoHistory = casinoHistoryArrayList.get(position);
        casinoHistoryViewHolder.historyView.setText("you got "   casinoHistory.getCoupon()   " at "   casinoHistory.getDate());
    }

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

ViewHolder class

package com.example.sololeveling.ViewHolder;

import android.util.Log;
import android.view.View;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.recyclerview.widget.RecyclerView;

import com.example.sololeveling.R;

public class CasinoHistoryViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener
{
    public TextView historyView;

    public CasinoHistoryViewHolder(@NonNull View itemView) {
        super(itemView);
        historyView = itemView.findViewById(R.id.historyview);
        Log.d("CasinoHistoryViewHolder","inside");
    }

    @Override
    public void onClick(View view) {

    }
}

main activity xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout 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=".HistoryActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@ id/historyrollview"
        android:layout_width="412dp"
        android:layout_height="729dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.0"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

item list xml

<?xml version="1.0" encoding="utf-8"?>
<com.google.android.material.card.MaterialCardView 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="75dp"
    android:clickable="true"
    android:focusable="true"
    app:cardUseCompatPadding="true">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:padding="10dp">

        <TextView
            android:id="@ id/historyview"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="daily task"
            android:textAppearance="@style/TextAppearance.AppCompat.Large" />
    </LinearLayout>

</com.google.android.material.card.MaterialCardView>

uj5u.com熱心網友回復：

更改資料后呼叫 notifyDataSetChanged() 方法。這個 android 函式通知附加的觀察者底層資料已更改，并且任何反映資料集的視圖都應自行重繪。

public void setCasinoHistoryArrayList(ArrayList<CasinoHistory> casinoHistories)
{
    this.casinoHistoryArrayList = casinoHistories;
    notifyDataSetChanged();
}

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