创建新活动后如何显示 RecyclerView，Android Firebase

Question

When my Home fragment uses regular buttons through intent to go to a new class. On the new class when I try to use RecylerVie and Firebase to show data, the data does not appear and the app crashes.

On my Firebase the nodes go from project --> to DataHome --> Home1. Home 1 has the attributes description,directions, ingredients, image, title

DataHome also has other nodes named Home2, etc. But in this case I'm only trying to show data from Home1 on this class.

database image

The logcat says Fatal Exception Main: Process: com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.tmrecipes.Model.DataHome

This is the class:

public class BeefSamosa extends AppCompatActivity {


    FirebaseDatabase mHomeFireBaseDatabase;
    RecyclerView myhomeview;
    private DatabaseReference DataHomeRef;
    private LinearLayoutManager mLinearLayoutManager;


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_beef_samosa);
        //Back Button
        getSupportActionBar().setDisplayShowHomeEnabled(true);
        getSupportActionBar().setDisplayHomeAsUpEnabled(true);
        getSupportActionBar().setTitle("Beef Samosa");


        //Recycler View
        myhomeview = findViewById(R.id.beefview);
        myhomeview.setHasFixedSize(true);

        //set layout as LinearLayout
        myhomeview.setLayoutManager(new LinearLayoutManager(this));


        //send query to firebase database
        mHomeFireBaseDatabase = FirebaseDatabase.getInstance();
        DataHomeRef = mHomeFireBaseDatabase.getInstance().getReference("DataHome").child("Home1");


    }

    @Override
    public boolean onOptionsItemSelected (MenuItem item){
        int id = item.getItemId();

        if(id == android.R.id.home){
            //ends the activity
            this.finish();
        }
        return super.onOptionsItemSelected(item);
    }



    @Override
    protected void onStart() {
        super.onStart();


        Query query = FirebaseDatabase.getInstance()
                .getReference("DataHome")
                .child("Home1");

        FirebaseRecyclerOptions<DataHome> options =
                new FirebaseRecyclerOptions.Builder<DataHome>()
                        .setQuery(DataHomeRef, DataHome.class)
                        .build();

        FirebaseRecyclerAdapter<DataHome,DataHomeViewHolder> firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<DataHome, DataHomeViewHolder>(options) {
            @NonNull
            @Override
            public DataHomeViewHolder onCreateViewHolder(ViewGroup parent, int viewtype) {
                final View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.activity_home_deatil, parent, false);

                return new DataHomeViewHolder(view);

            }

            @Override
            protected void onBindViewHolder(@NonNull DataHomeViewHolder holder, int position, @NonNull DataHome model) {
                    holder.setDetails(getApplicationContext(), model.getTitle(), model.getImage(), model.getDescription() , model.getIngredients(), model.getDirections());
            }
        };

        firebaseRecyclerAdapter.startListening();
        myhomeview.setAdapter(firebaseRecyclerAdapter);
    }


    //DataHomeViewHolder class

    public static class DataHomeViewHolder extends RecyclerView.ViewHolder {


        View mview;


        public DataHomeViewHolder(@NonNull View itemView) {
            super(itemView);
            mview = itemView;



        }

        public void setDetails(Context ctx, String title, String image, String description, String ingredients , String directions) {

            //Views
            TextView mHomeTitle = mview.findViewById(R.id.titlewords);
            ImageView mHomeImage = mview.findViewById(R.id.loading_pic);
            TextView mDescriptionTitle = mview.findViewById(R.id.descriptionwords);
            TextView mIngredientsTitle = mview.findViewById(R.id.ingredientwords);
            TextView mDirectionsTitle = mview.findViewById(R.id.directionwords);

            //Set data to views
            mHomeTitle.setText(title);
            mDescriptionTitle.setText(description);
            mIngredientsTitle.setText(ingredients);
            mDirectionsTitle.setText(directions);
            Picasso.get().load(image).into(mHomeImage);

        }


    }
}

My model class is:

 public class DataHome {

        public String title ,image, description, ingredients, directions;

        public String getTitle() {
            return title;
        }

        public void setTitle(String title) {
            this.title = title;
        }

        public String getImage() {
            return image;
        }

        public void setImage(String image) {
            this.image = image;
        }

        public String getDescription() {
            return description;
        }

        public void setDescription(String description) {
            this.description = description;
        }

        public String getIngredients() {
            return ingredients;
        }

        public void setIngredients(String ingredients) {
            this.ingredients = ingredients;
        }

        public String getDirections() {
            return directions;
        }

        public void setDirections(String directions) {
            this.directions = directions;
        }

        public DataHome(String title, String image, String description, String ingredients, String directions){
            this.title =title;
            this.image = image;
            this.description = description;
                this.ingredients = ingredients;
                this.directions=directions;
            }

    }

Edit: The changed class is:

public class BeefSamosa extends AppCompatActivity {

private FirebaseRecyclerAdapter firebaseRecyclerAdapter;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_beef_samosa);
    //Back Button
    getSupportActionBar().setDisplayShowHomeEnabled(true);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    getSupportActionBar().setTitle("Beef Samosa");


    RecyclerView recyclerView = findViewById(R.id.beef_view);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    DatabaseReference rootRef = FirebaseDatabase.getInstance().getReference();
    Query query = rootRef.child("DataHome");

    FirebaseRecyclerOptions<DataHome> firebaseRecyclerOptions = new FirebaseRecyclerOptions.Builder<DataHome>()
            .setQuery(query, DataHome.class)
            .build();


    firebaseRecyclerAdapter = new FirebaseRecyclerAdapter<DataHome, DataHomeViewHolder>(firebaseRecyclerOptions) {
        @Override
        protected void onBindViewHolder(@NonNull DataHomeViewHolder dataHomeViewHolder, int position, @NonNull DataHome dataHome) {
            dataHomeViewHolder.setDataHome(dataHome);
        }

        @Override
        public DataHomeViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.homedetail, parent, false);

            return new DataHomeViewHolder(view);
        }
    };
    recyclerView.setAdapter(firebaseRecyclerAdapter);

}

@Override
protected void onStart() {
    super.onStart();
    firebaseRecyclerAdapter.startListening();
}

@Override
protected void onStop() {
    super.onStop();

    if (firebaseRecyclerAdapter!= null) {
        firebaseRecyclerAdapter.stopListening();
    }
}


@Override
public boolean onOptionsItemSelected (MenuItem item){
    int id = item.getItemId();

    if(id == android.R.id.home){
        //ends the activity
        this.finish();
    }
    return super.onOptionsItemSelected(item);
}





//DataHomeViewHolder class

private class DataHomeViewHolder extends RecyclerView.ViewHolder {

    private TextView imagetoo, titletext, description, ingredients, directions;


    DataHomeViewHolder(View itemView){
        super(itemView);
        imagetoo = itemView.findViewById(R.id.imagetoo);
        titletext = itemView.findViewById(R.id.titletext);
        description = itemView.findViewById(R.id.description);
        ingredients = itemView.findViewById(R.id.ingredients);
        directions = itemView.findViewById(R.id.directions);
    }


    void setDataHome(DataHome DataHome) {
        String imageto = DataHome.getImage();
        imagetoo.setText(imageto);
        String titleto = DataHome.getTitle();
        titletext.setText(titleto);
        String descriptionto = DataHome.getDescription();
        description.setText(descriptionto);
        String ingredientsto = DataHome.getIngredients();
        ingredients.setText(ingredientsto);
        String directionsto = DataHome.getDirections();
        directions.setText(directionsto);
    }
}

}

Answer 1

You are getting the following error:

 Fatal Exception Main: Process: com.google.firebase.database.DatabaseException: Can't convert object of type java.lang.String to type com.example.tmrecipes.Model.DataHome

Because the children under Home1 node are strings and not DataHome objects. To solve this, you need to pass to your FirebaseRecyclerOptions object a query that points to a node where DataHome objects exist. So please change the following line of code:

Query query = FirebaseDatabase.getInstance()
            .getReference("DataHome")
            .child("Home1");

to

Query query = FirebaseDatabase.getInstance()
            .getReference("DataHome");

See, I have removed the call to .child("Home1") because this is producing the error. This change will help you display all DataHome objects that exist within the all DataHome node.

If you want to display only the details of Home1 for example, there is no need to use the Firebase-UI library, you can simply get the value of all properties and display them in a list as explained in my answer from this post:

• How can I retrieve data from Firebase to my adapter