我需要帮助来显示从SQLite到Recyclerview的数据

Question

我正在创建一个显示我的食物清单的应用。我想通过回收者视图在主要活动中显示列表，但是出现错误，我尝试运行调试器，但是它不断跳入系统类，我在偏好设置-调试器-步进中添加了android。*，但它不起作用。这是我第一次从事自己的项目。感谢您的回答

这是我的适配器

 public class CookingAdapter extends RecyclerView.Adapter<CookingAdapter.Viewholder>{

ArrayList<Food> foodList= new ArrayList<>();
private String name;
private int imageID;

public CookingAdapter(ArrayList<Food>foods) {
    foodList=foods;
}
 public static class Viewholder extends RecyclerView.ViewHolder{
    CardView cardView;
    public Viewholder(@NonNull CardView itemView) {
        super(itemView);
        cardView= itemView;
    }
}


    @NonNull
    @Override
    public Viewholder onCreateViewHolder(@NonNull ViewGroup viewGroup, int i) {
     CardView cv =(CardView) LayoutInflater.from(viewGroup.getContext()).
             inflate(R.layout.layout_cardview,viewGroup,false);
        return new Viewholder(cv);
    }

    @Override
    public void onBindViewHolder(@NonNull Viewholder viewholder, final int position) {
        CardView cv = viewholder.cardView;
        ImageView imageView = (ImageView)cv.findViewById(R.id.info_image);
        Drawable drawable = ContextCompat.getDrawable(cv.getContext(),
                foodList.get(position).getImageId());
        imageView.setImageDrawable(drawable);
        imageView.setContentDescription(foodList.get(position).getName());
        TextView textView  = (TextView)cv.findViewById(R.id.info_text);
        textView.setText(foodList.get(position).getName());
    }

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

食物课

public class Food {
private String name;
private String recipe;
private int imageId;
private int favorite;

public Food(String name, String recipe, int imageId, int favorite) {
    this.name = name;
    this.recipe = recipe;
    this.imageId = imageId;
    this.favorite = favorite;
}

public Food(ArrayList<Food>foods, final int position) {
    this.name = foods.get(position).getName();
    this.recipe = foods.get(position).getRecipe();
    this.imageId = foods.get(position).getImageId();
    this.favorite = foods.get(position).getFavorite();
}

public String getName() {
    return name;
}

public String getRecipe() {
    return recipe;
}

public int getImageId() {
    return imageId;
}

public int getFavorite() {
    return favorite;
}

} 数据库

 public class CookingDatabase extends SQLiteOpenHelper {
private static final String DB_NAME="Cooking";
private static final int DB_VERSION = 1;
private ArrayList<Food>foods = new ArrayList<>();

// Database Constructor
public CookingDatabase(Context context) {
    super(context, DB_NAME,null, DB_VERSION);
}

@Override
public void onCreate(SQLiteDatabase db) {
    updateDatabase(db,0,DB_VERSION);
}

@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {

}

private void insert(SQLiteDatabase db,String name,String recipe, int imageID, int favortie)
{
    ContentValues cookingValue = new ContentValues();
    cookingValue.put("NAME",name);
    cookingValue.put("RECIPE",recipe);
    cookingValue.put("IMAGE_ID",imageID);
    cookingValue.put("FAVORITE",favortie);
    db.insert(DB_NAME,null,cookingValue);
}

private void updateDatabase(SQLiteDatabase db,int oldVer, int newVer){
    String table="CREATE TABLE COOKING"+"(_id INTEGER PRIMARY KEY AUTOINCREMENT," +
            " "+" NAME TEXT, "+" RECIPE TEXT, "+"IMAGE_ID INTEGER,"+"FAVORITE INTEGER)";
    if(oldVer < 1){
        db.execSQL(table);
        insert(db,"Pizza","Bake in 10 minutes",R.drawable.pizza,0);
        insert(db,"Steak","Salt and pepper",R.drawable.steak,0);
        insert(db,"Sushi","Fresh Salmon",R.drawable.sushi,0);
    }
}

public ArrayList<Food> getData(){
    SQLiteDatabase db;
    String row="select * from " + DB_NAME;
    db= this.getReadableDatabase();
    Cursor cursor = db.rawQuery(row,null);
    if(cursor != null){
        if(cursor.moveToFirst()){
            do {
                foods.add(new Food(cursor.getString(cursor.getColumnIndex("NAME")), 
                        cursor.getString(cursor.getColumnIndex("RECIPE")),
                        cursor.getInt(2),cursor.getInt(3)));
            }while (cursor.moveToNext());
        }
    }
    cursor.close();
    db.close();
    return foods;
}

public ArrayList<Food> getFoods() {
    return foods;
}

}

MainActivity

 public class MainActivity extends AppCompatActivity {
CookingDatabase db= new CookingDatabase(this);

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
    setSupportActionBar(toolbar);
    RecyclerView recyclerView=(RecyclerView)findViewById(R.id.id_recycler);
    CookingAdapter adapter = new CookingAdapter(db.getData());
    recyclerView.setAdapter(adapter);
    GridLayoutManager gridLayoutManager = new GridLayoutManager(this,2);
    recyclerView.setLayoutManager(gridLayoutManager);
}

} MainActivyti XML

 LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical"
tools:context="hfad.com.mycooking.MainActivity">

    <include
        layout="@layout/toolbar_main"
        android:id="@+id/toolbar"/>

<android.support.v7.widget.RecyclerView
xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/pizza_recycler"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:scrollbars="vertical" /></LinearLayout>

Logcat

   2019-02-09 16:19:14.238 3503-3503/hfad.com.mycooking E/AndroidRuntime: FATAL EXCEPTION: main
Process: hfad.com.mycooking, PID: 3503
android.content.res.Resources$NotFoundException: Resource ID #0x0
    at android.content.res.ResourcesImpl.getValue(ResourcesImpl.java:190)
    at android.content.res.Resources.getDrawable(Resources.java:766)
    at android.content.Context.getDrawable(Context.java:525)
    at android.support.v4.content.ContextCompat.getDrawable(ContextCompat.java:463)
    at hfad.com.mycooking.CookingAdapter.onBindViewHolder(CookingAdapter.java:45)
    at hfad.com.mycooking.CookingAdapter.onBindViewHolder(CookingAdapter.java:17)
    at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6781)
    at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6823)
    at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5752)
    at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:6019)
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5858)
    at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5854)
    at android.support.v7.widget.LinearLayoutManager$LayoutState.next(LinearLayoutManager.java:2230)
    at android.support.v7.widget.GridLayoutManager.layoutChunk(GridLayoutManager.java:557)
    at android.support.v7.widget.LinearLayoutManager.fill(LinearLayoutManager.java:1517)
    at android.support.v7.widget.LinearLayoutManager.onLayoutChildren(LinearLayoutManager.java:612)
    at android.support.v7.widget.GridLayoutManager.onLayoutChildren(GridLayoutManager.java:171)
    at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3924)
    at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3641)
    at android.support.v7.widget.RecyclerView.onLayout(RecyclerView.java:4194)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1741)
    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1585)
    at android.widget.LinearLayout.onLayout(LinearLayout.java:1494)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.widget.FrameLayout.layoutChildren(FrameLayout.java:323)
    at android.widget.FrameLayout.onLayout(FrameLayout.java:261)
    at com.android.internal.policy.DecorView.onLayout(DecorView.java:724)
    at android.view.View.layout(View.java:17523)
    at android.view.ViewGroup.layout(ViewGroup.java:5612)
    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:2342)
    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2069)
    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1246)
    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6301)
    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871)
2019-02-09 16:19:14.238 3503-3503/hfad.com.mycooking E/AndroidRuntime:     at android.view.Choreographer.doCallbacks(Choreographer.java:683)
    at android.view.Choreographer.doFrame(Choreographer.java:619)
    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857)
    at android.os.Handler.handleCallback(Handler.java:751)
    at android.os.Handler.dispatchMessage(Handler.java:95)
    at android.os.Looper.loop(Looper.java:154)
    at android.app.ActivityThread.main(ActivityThread.java:6077)
    at java.lang.reflect.Method.invoke(Native Method)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:866)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:756)

Answer 1

android.content.res.Resources$NotFoundException: Resource ID #0x0
    at android.content.res.ResourcesImpl.getValue(ResourcesImpl.java:190)
    at android.content.res.Resources.getDrawable(Resources.java:766)
    at android.content.Context.getDrawable(Context.java:525)
    at android.support.v4.content.ContextCompat.getDrawable(ContextCompat.java:463)
    at hfad.com.mycooking.CookingAdapter.onBindViewHolder(CookingAdapter.java:45)
    at hfad.com.mycooking.CookingAdapter.onBindViewHolder(CookingAdapter.java:17)

这些行表明您的Viewholder在绑定视图时找不到资源：

@Override
public void onBindViewHolder(@NonNull Viewholder viewholder, final int position) {
        CardView cv = viewholder.cardView;
        ImageView imageView = (ImageView)cv.findViewById(R.id.info_image);
        Drawable drawable = ContextCompat.getDrawable(cv.getContext(),
                foodList.get(position).getImageId());
        imageView.setImageDrawable(drawable);
        imageView.setContentDescription(foodList.get(position).getName());
        TextView textView  = (TextView)cv.findViewById(R.id.info_text);
        textView.setText(foodList.get(position).getName());
    }

特别是，我的猜测是问题出在这里：

        Drawable drawable = ContextCompat.getDrawable(cv.getContext(),
                foodList.get(position).getImageId());
        imageView.setImageDrawable(drawable);

确保传递正确的资源ID。注意：存储资源ID并不是一个好主意

(R.drawable.example)

作为类字段

(foodList.get(position).getImageId())

用不同的资源映射它们，例如。带有枚举类：

public enum FoodType {

    PIZZA(R.drawable.pizza),
    BURGER(R.drawable.burger);
    private Integer drawableRes;
    private FoodType(Integer drawableRes){
        this.drawableRes = drawableRes;
    }

    public Integer getDrawableRes() {
        return drawableRes;
    }
}

然后，检查类型并按以下方式获取它：

FoodType type;
if(type==FoodType.BURGER){
    type.getDrawableRes();
}