Firebase DB-linked Recycler view has an error

Question

I'm a beginner at Android development. Firebase DB-linked Recycler view has an error. There are two errors in Frag1.java.

Frag1.java
'LinearLayoutManager(android.content.Context)' in 'androidx.recyclerview.widget.LinearLayoutManager' cannot be applied to '(softcampus.co.myapplication.Frag1)'
'ContentAdapter(java.util.ArrayList<softcampus.co.myapplication.Content>, android.content.Context)' in 'softcampus.co.myapplication.ContentAdapter' cannot be applied to '(java.util.ArrayList<softcampus.co.myapplication.Content>, softcampus.co.myapplication.Frag1)'

I'm having a hard time because the error was not resolved through the search...

Frag1.java

package softcampus.co.myapplication;

import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.ImageButton;
import android.widget.LinearLayout;
import android.widget.TextView;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.fragment.app.Fragment;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.google.firebase.database.DataSnapshot;
import com.google.firebase.database.DatabaseError;
import com.google.firebase.database.DatabaseReference;
import com.google.firebase.database.FirebaseDatabase;
import com.google.firebase.database.ValueEventListener;

import org.w3c.dom.Text;

import java.util.ArrayList;

public class Frag1 extends Fragment {

    private View view;
    private RecyclerView recyclerView;
    private RecyclerView.Adapter adapter;
    private RecyclerView.LayoutManager layoutManager;
    private ArrayList<Content> arrayList;
    private FirebaseDatabase database;
    private DatabaseReference databaseReference;

    TextView main_name;
    TextView main_board;
    Button main_plus;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
        view = inflater.inflate(R.layout.frag1_home, container, false);

        recyclerView = (RecyclerView)view.findViewById(R.id.recyclerView);
        recyclerView.setHasFixedSize(true);
        layoutManager = new LinearLayoutManager(this);
        recyclerView.setLayoutManager(layoutManager);
        arrayList = new ArrayList<>(); 

        database = FirebaseDatabase.getInstance(); 

        databaseReference = database.getReference("Content"); 
        databaseReference.addListenerForSingleValueEvent(new ValueEventListener() {
            @Override
            public void onDataChange(@NonNull DataSnapshot dataSnapshot) {
                
                arrayList.clear();
                for(DataSnapshot snapshot : dataSnapshot.getChildren()){ 
                    Content content = snapshot.getValue(Content.class); 
                    arrayList.add(content); 
                }
                adapter.notifyDataSetChanged();
            }

            @Override
            public void onCancelled(@NonNull DatabaseError databaseError) {
                Log.e("Frag1",String.valueOf(databaseError.toException()));
            }
        });

        adapter = new ContentAdapter(arrayList, this);
        recyclerView.setAdapter(adapter);

        main_name = (TextView)view.findViewById(R.id.main_name);
        main_board = (TextView) view.findViewById(R.id.main_board);
        main_plus = (Button) view.findViewById(R.id.main_plus);

        main_plus.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent  = new Intent(view.getContext(), Campaign_registration.class);
                startActivity(intent);
            }
        });

        return view;
    }

}

frag1_home.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"
    android:orientation="vertical">


    <TextView
        android:id="@+id/main_name"
        android:layout_width="365dp"
        android:layout_height="wrap_content"
        android:text="안녕하세요, OOO님!"
        android:textSize="25sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.1" />

    <Button
        android:id="@+id/main_plus"
        android:layout_width="35dp"
        android:layout_height="35dp"
        android:background="@drawable/ic_baseline_add_circle_24"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.906"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.181" />

    <TextView
        android:id="@+id/main_board"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="게시판"
        android:textSize="22sp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintHorizontal_bias="0.148"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="0.186" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="560dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintVertical_bias="1.0">

        <ScrollView
            android:layout_width="match_parent"
            android:layout_height="match_parent">

            <androidx.recyclerview.widget.RecyclerView
                android:id="@+id/recyclerView"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:orientation="vertical"
                app:layoutManager="androidx.recyclerview.widget.LinearLayoutManager" />

        </ScrollView>


    </LinearLayout>

</androidx.constraintlayout.widget.ConstraintLayout>

Content.java

package softcampus.co.myapplication;

public class Content {
    private String pro_img;
    private String campagin_name;
    private int token_goal;
    private String text;

    public Content(){};

    public String getPro_img() {
        return pro_img;
    }

    public void setPro_img(String pro_img) {
        this.pro_img = pro_img;
    }

    public String getCampagin_name() {
        return campagin_name;
    }

    public void setCampagin_name(String campagin_name) {
        this.campagin_name = campagin_name;
    }

    public int getToken_goal() {
        return token_goal;
    }

    public void setToken_goal(int token_goal) {
        this.token_goal = token_goal;
    }

    public String getText() { return text;}

    public void setText(String text) { this.text = text; }
}

ContentAdapter.java

package softcampus.co.myapplication;

import android.content.Context;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;

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

import com.bumptech.glide.Glide;

import java.util.ArrayList;

public class ContentAdapter extends RecyclerView.Adapter<ContentAdapter.ContentViewHolder> {

    private ArrayList<Content> arrayList;
    private Context context;


    public ContentAdapter(ArrayList<Content> arrayList, Context context) {
        this.arrayList = arrayList;
        this.context = context;
    }


    @NonNull
    @Override
    public ContentViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.content_item,parent,false);
        ContentViewHolder holder = new ContentViewHolder(view);

        return holder;
    }

    @Override
    public void onBindViewHolder(@NonNull ContentViewHolder holder, int position) {
        Glide.with(holder.itemView)
                .load(arrayList.get(position).getPro_img())
                .into(holder.iv_profile);
        holder.tv_name.setText(arrayList.get(position).getCampagin_name());
        holder.tv_goal.setText(arrayList.get(position).getToken_goal());
    }

    @Override
    public int getItemCount() {
        //삼항 연산자
        return (arrayList != null ? arrayList.size() : 0);
    }

    public class ContentViewHolder extends RecyclerView.ViewHolder {
        ImageView iv_profile;
        TextView tv_name;
        TextView tv_goal;

        public ContentViewHolder(@NonNull View itemView) {
            super(itemView);
            this.iv_profile = itemView.findViewById(R.id.iv_profile);
            this.tv_name = itemView.findViewById(R.id.tv_name);
            this.tv_goal = itemView.findViewById(R.id.tv_goal);
        }
    }
}

content_item.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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="wrap_content">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">

            <ImageView
                android:id="@+id/iv_profile"
                android:layout_width="80dp"
                android:layout_height="80dp"
                android:layout_margin="5dp"
                app:srcCompat="@android:drawable/ic_menu_gallery" />

                <LinearLayout
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:orientation="vertical"
                    android:layout_marginLeft="5dp">

                    <TextView
                        android:id="@+id/tv_name"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:text="캠페인명"
                        android:textSize="27sp"
                        android:layout_marginTop="14dp"/>

                    <TextView
                        android:id="@+id/tv_goal"
                        android:layout_width="match_parent"
                        android:layout_height="wrap_content"
                        android:text="목표 토큰"
                        android:textSize="18sp"
                        android:layout_marginTop='3dp'/>

                </LinearLayout>
    </LinearLayout>

</LinearLayout>

This issue has been troubling me for weeks and I can't seem to find a solution to it. Thanks in advance for the help.

Answer 1

• for the first error either set the LinearLayoutManager programmatically or in xml but don't use both at the same time and use requireContext() instead of this when setting it programmatically

    layoutManager = new LinearLayoutManager(this);
    layoutManager = new LinearLayoutManager(requireContext());
  

• for the second one You are using this for context in a fragment, use requireContext()

    adapter = new ContentAdapter(arrayList, this);
    adapter = new ContentAdapter(arrayList, requireContext());
  

• Third, why is your recyclerview in a scrollview, inside a linearlayout? Consider adding it to the ConstraintLayout as a child?

• Fourth, consider removing the nested LinearLayout in content_item