java - 当我尝试将数据从 firebase 数据库添加到 firebaseViewHolder 时，Android 应用程序不断停止

Question

我正在开发一个食谱书应用程序。我的数据结构如下:

 Reference
   - users
     -53
     -movies
       -id1
          (-name
          -rating
          -ingredients(list)
          -recipe
          -photo)
       -id2 (....)

数据添加正确，但是当我使用以下代码进行检索时，应用程序停止。我的模型类是食谱。

1. 我需要创建一个网格结构来显示所有菜肴。我认为这段代码应该达到这个目的，但事实并非如此。我做错了什么？

2. 当用户单击特定菜肴时，应显示该菜肴的食谱和其他详细信息。我如何在 firebase 中进行这种选择性检索？

   package foodelicious.com.foodfinal;
   
   public class MainActivity extends AppCompatActivity {
   
   private FloatingActionButton fab;
   
   ScaleAnimation shrinkAnim;
   private RecyclerView mRecyclerView;
   private StaggeredGridLayoutManager mLayoutManager;
   private TextView tvNoRecipes;
   
   private ImageView DPoster;
   private TextView  DMovieName,DIngredients,DRecipeTitle,DRecipe;
   private RatingBar Drate;
   
   
   //Getting reference to Firebase Database
   FirebaseDatabase database = FirebaseDatabase.getInstance();
   DatabaseReference mDatabaseReference = database.getReference();
   
   private static final String userId = "53";
   
   
   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
   
       //Initializing our Recyclerview
       mRecyclerView = (RecyclerView) findViewById(R.id.my_recycler_view);
       tvNoRecipes = (TextView) findViewById(R.id.tv_no_recipes);
   
       DPoster=(ImageView) findViewById(R.id.Dposter);
       DIngredients=(TextView) findViewById(R.id.Ding);
       //scale animation to shrink floating actionbar
       shrinkAnim = new ScaleAnimation(1.15f, 0f, 1.15f, 0f, Animation.RELATIVE_TO_SELF, 0.5f, Animation.RELATIVE_TO_SELF, 0.5f);
   
       if (mRecyclerView != null) {
           //to enable optimization of recyclerview
           mRecyclerView.setHasFixedSize(true);
       }
       //using staggered grid pattern in recyclerview
       mLayoutManager = new StaggeredGridLayoutManager(2, StaggeredGridLayoutManager.VERTICAL);
       mRecyclerView.setLayoutManager(mLayoutManager);
   
       //Say Hello to our new FirebaseUI android Element, i.e., FirebaseRecyclerAdapter
       FirebaseRecyclerAdapter<Recipe,RecipeViewHolder> adapter = new FirebaseRecyclerAdapter<Recipe, RecipeViewHolder>(
               Recipe.class,
               R.layout.recipe_board_item,
               RecipeViewHolder.class,
               //referencing the node where we want the database to store the data from our Object
               mDatabaseReference.child("users").child(userId).child("movies").getRef()
       ) {
           @Override
           protected void populateViewHolder(final RecipeViewHolder viewHolder, Recipe model, int position) {
               if(tvNoRecipes.getVisibility()== View.VISIBLE){
                   tvNoRecipes.setVisibility(View.GONE);
   
               }
               viewHolder.tvRecipeName.setText(model.getRecipeName());
               viewHolder.ratingBar.setRating(model.getRecipeRating());
               Picasso.with(MainActivity.this).load(model.getRecipePoster()).into(viewHolder.ivRecipePoster);
   
               viewHolder.ivRecipePoster.setOnClickListener(new View.OnClickListener() {
   
                   @Override
                   public void onClick(View view) {
   
                       setContentView(R.layout.recipe_details);
   
                   }
               });
           }
       };
   
       mRecyclerView.setAdapter(adapter);
   
   
       fab = (FloatingActionButton) findViewById(R.id.fab);
       fab.setOnClickListener(new View.OnClickListener() {
           public void onClick(View v) {
               getSupportFragmentManager().beginTransaction()
                       .replace(R.id.frame_container, new AddRecipeFragment())
                       .addToBackStack(null)
                       .commit();
               //animation being used to make floating actionbar disappear
               shrinkAnim.setDuration(400);
               fab.setAnimation(shrinkAnim);
               shrinkAnim.start();
               shrinkAnim.setAnimationListener(new Animation.AnimationListener() {
                   @Override
                   public void onAnimationStart(Animation animation) {
   
                   }
   
                   @Override
                   public void onAnimationEnd(Animation animation) {
                       //changing floating actionbar visibility to gone on animation end
                       fab.setVisibility(View.GONE);
                   }
   
                   @Override
                   public void onAnimationRepeat(Animation animation) {
   
   
                   }
               });
   
           }
       });
   
   
   }
   
   
   @Override
   public void onBackPressed() {
       super.onBackPressed();
       if (fab.getVisibility() == View.GONE)
           fab.setVisibility(View.VISIBLE);
   }
   
   
   
   //ViewHolder for our Firebase UI
   public static class RecipeViewHolder extends RecyclerView.ViewHolder{
   
       TextView tvRecipeName;
       RatingBar ratingBar;
       ImageView ivRecipePoster;
   
       public RecipeViewHolder(View v) {
           super(v);
           tvRecipeName = (TextView) v.findViewById(R.id.iv_dish_name);
           ratingBar = (RatingBar) v.findViewById(R.id.rating_bar);
           ivRecipePoster = (ImageView) v.findViewById(R.id.iv_dish_poster);
   
       }
   }
   }
   

LOGCAT

10-05 16:43:08.462 30349-30479/foodelicious.com.foodfinal D/FA: Connected to remote service 10-05 16:43:08.463 30349-30479/foodelicious.com.foodfinal V/FA: Processing queued up service tasks: 1 10-05 16:43:13.592 30349-30479/foodelicious.com.foodfinal V/FA: Inactivity, disconnecting from the service 10-05 16:43:21.549 30349-30354/foodelicious.com.foodfinal I/art: Do partial code cache collection, code=29KB, data=29KB 10-05 16:43:21.550 30349-30354/foodelicious.com.foodfinal I/art: After code cache collection, code=29KB, data=29KB 10-05 16:43:21.550 30349-30354/foodelicious.com.foodfinal I/art: Increasing code cache capacity to 128KB 10-05 16:43:21.617 30349-30349/foodelicious.com.foodfinal D/AndroidRuntime: Shutting down VM 10-05 16:43:21.625 30349-30349/foodelicious.com.foodfinal E/AndroidRuntime: FATAL EXCEPTION: main Process: foodelicious.com.foodfinal, PID: 30349 com.google.firebase.database.DatabaseException: Class foodelicious.com.foodfinal.models.Recipe is missing a constructor with no arguments at com.google.android.gms.internal.zzbqi$zza.zze(Unknown Source) at com.google.android.gms.internal.zzbqi$zza.zzaG(Unknown Source) at com.google.android.gms.internal.zzbqi.zze(Unknown Source) at com.google.android.gms.internal.zzbqi.zzb(Unknown Source) at com.google.android.gms.internal.zzbqi.zza(Unknown Source) at com.google.firebase.database.DataSnapshot.getValue(Unknown Source) at com.firebase.ui.database.FirebaseRecyclerAdapter.parseSnapshot(FirebaseRecyclerAdapter.java:147) at com.firebase.ui.database.FirebaseRecyclerAdapter.getItem(FirebaseRecyclerAdapter.java:136) at com.firebase.ui.database.FirebaseRecyclerAdapter.onBindViewHolder(FirebaseRecyclerAdapter.java:176) at android.support.v7.widget.RecyclerView$Adapter.onBindViewHolder(RecyclerView.java:6476) at android.support.v7.widget.RecyclerView$Adapter.bindViewHolder(RecyclerView.java:6509) at android.support.v7.widget.RecyclerView$Recycler.tryBindViewHolderByDeadline(RecyclerView.java:5452) at android.support.v7.widget.RecyclerView$Recycler.tryGetViewHolderForPositionByDeadline(RecyclerView.java:5718) at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5557) at android.support.v7.widget.RecyclerView$Recycler.getViewForPosition(RecyclerView.java:5553) at android.support.v7.widget.LayoutState.next(LayoutState.java:100) at android.support.v7.widget.StaggeredGridLayoutManager.fill(StaggeredGridLayoutManager.java:1570) at android.support.v7.widget.StaggeredGridLayoutManager.onLayoutChildren(StaggeredGridLayoutManager.java:682) at android.support.v7.widget.StaggeredGridLayoutManager.onLayoutChildren(StaggeredGridLayoutManager.java:604) at android.support.v7.widget.RecyclerView.dispatchLayoutStep2(RecyclerView.java:3693) at android.support.v7.widget.RecyclerView.dispatchLayout(RecyclerView.java:3410) at android.support.v7.widget.RecyclerView.consumePendingUpdateOperations(RecyclerView.java:1710) at android.support.v7.widget.RecyclerView$1.run(RecyclerView.java:346) at android.view.Choreographer$CallbackRecord.run(Choreographer.java:871) at android.view.Choreographer.doCallbacks(Choreographer.java:683) at android.view.Choreographer.doFrame(Choreographer.java:616) at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:857) at android.os.Handler.handleCallback(Handler.java:751) at android.os.Handler.dispatchMessage(Handler.java:95) at android.os.Looper.loop(Looper.java:154) at android.app.ActivityThread.main(ActivityThread.java:6123) at java.lang.reflect.Method.invoke(Native Method) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:757)

Answer 1

错误:

com.google.firebase.database.DatabaseException: Class foodelicious.com.foodfinal.models.Recipe is missing a constructor with no arguments at

解决方案:将默认(无参数)构造函数添加到您的类Recipe

public class Recipe ... {

   public Recipe() {
       //
   }


}