java - RecyclerView + SQLite 空白页

Question

我没有收到任何错误，但页面是空白的。

我有 2 种 View 布局，一种用于回收器 View (acrivity_favorites)，另一种用于图像和其他 View (favorites_item)，我如何在FavoritesActivity.java 文件中膨胀 View

FavoritesActivity.java(此代码需要一些修改和帮助)

public class FavoritesActivity extends AppCompatActivity {

    RecyclerView recyclerView;
    RecyclerView.LayoutManager layoutManager;

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

        recyclerView = findViewById(R.id.recycler_favorites);
        recyclerView.setHasFixedSize(true);

        LinearLayoutManager myLayoutManager = new LinearLayoutManager(this);
        myLayoutManager.setReverseLayout(true);
        myLayoutManager.setStackFromEnd(true);
        recyclerView.setLayoutManager(myLayoutManager);

        loadFavorites();
    }

    private void loadFavorites() {

        FavoritesAdapter adapter = new FavoritesAdapter
                (this, new Database(this).getAllFavorites("FoodId"));

        recyclerView.setAdapter(adapter);

    }

}

这里是FavoritesAdapter.java

public class FavoritesAdapter extends RecyclerView.Adapter<FavoritesViewHolder> {

    private Context context;
    private List<Favorites> favoritesList;

    public FavoritesAdapter(Context context, List<Favorites> favoritesList) {
        this.context = context;
        this.favoritesList = favoritesList;
    }

    @NonNull
    @Override
    public FavoritesViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View itemView = LayoutInflater.from(context).inflate(R.layout.favorites_item,parent,false);
        return new FavoritesViewHolder(itemView);
    }

    @Override
    public void onBindViewHolder(@NonNull FavoritesViewHolder viewHolder, final int position) {

        viewHolder.food_name.setText(favoritesList.get(position).getName());
        viewHolder.food_presenter.setText(String.format("%S", favoritesList.get(position).getName()));
        Picasso.with(context).load(favoritesList.get(position).getImage())
                .into(viewHolder.food_image);

        final Favorites local = favoritesList.get(position);
        viewHolder.setItemClickListener(new ItemClickListener() {
            @Override
            public void onClick(View view, int position, boolean isLongClick) {

                //Start New Activity (Description Activity)
                Intent foodDetails = new Intent(context, FavoritesActivity.class);
                foodDetails.putExtra("FoodId",favoritesList.get(position).getFoodId()); //Send food ID to new activity
                context.startActivity(foodDetails);
            }
        });

    }

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

    public void removeItem(int position){
        favoritesList.remove(position);
        notifyItemRemoved(position);
    }

    public void restoreItem(Favorites item, int position){
        favoritesList.add(position,item);
        notifyItemInserted(position);
    }

    public Favorites getItem(int position){
        return favoritesList.get(position);
    }

}

数据库.java

 public List<Favorites> getAllFavorites (String foodId)
    {
        SQLiteDatabase db = getReadableDatabase();
        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();

        String[] sqlSelect={"FoodId", "Name", "Image", "Description", "Components", "MenuId", "UserName"};
        String sqlTable = "Favorites";

        qb.setTables(sqlTable);
        Cursor cursor = qb.query(db,sqlSelect,"FoodId=?", new String[]{foodId}, null,null,null);

        final List<Favorites> result = new ArrayList<>();
        if (cursor.moveToFirst())
        {
            do {
                result.add(new Favorites(
                        cursor.getString(cursor.getColumnIndex("FoodId")),
                        cursor.getString(cursor.getColumnIndex("Name")),
                        cursor.getString(cursor.getColumnIndex("Image")),
                        cursor.getString(cursor.getColumnIndex("Description")),
                        cursor.getString(cursor.getColumnIndex("Components")),
                        cursor.getString(cursor.getColumnIndex("MenuId")),
                        cursor.getString(cursor.getColumnIndex("UserName"))
                        ));
            }while (cursor.moveToNext());
        }
        return result;
    }

activity_favorites.XML(用于回收站 View )

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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:id="@+id/root_layout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".FoodList">

        <android.support.v7.widget.RecyclerView
        android:layout_below="@+id/searchBar"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/recycler_favorites"
        android:scrollbars="vertical"
        >

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


</RelativeLayout>

favorites_item.XML(用于在回收器 View 中显示图像和所有详细信息)

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="300dp"
    app:cardElevation="10dp"
    app:cardCornerRadius="0dp"
    android:layout_marginBottom="8dp"
    >

       <LinearLayout
        android:id="@+id/view_foreground"
        android:layout_margin="8dp"
        android:background="@android:color/white"
        android:orientation="vertical"
        android:weightSum="5"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:padding="10dp"
        android:gravity="right"
        >


        <ImageView
            android:id="@+id/food_image"
            android:src="@drawable/bacground"
            android:scaleType="centerCrop"
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="4"
            />

        <LinearLayout
            android:layout_width="match_parent"
            android:layout_height="0dp"
            android:layout_weight="1"
            android:orientation="horizontal"
            android:weightSum="10">

                <TextView
                android:id="@+id/food_name"
                android:layout_width="0dp"
                android:layout_height="wrap_content"
                android:layout_weight="8"
                android:gravity="right"
                android:text="Name Of Food"
                android:textSize="20sp" />

        </LinearLayout>


    </LinearLayout>

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

Answer 1

检查以下几行时。

 FavoritesAdapter adapter = new FavoritesAdapter
                (this, new Database(this).getAllFavorites("foodId"));

Cursor cursor = qb.query(db,sqlSelect,"FoodId=?", new String[]{foodId}, null,null,null);

您的条件类似于 FoodId ="foodId"列的值。这就是计数为零的原因。请检查。