滚动图像时，Android Studio RecyclerView严重滞后

Question

I have a RecyclerView filled by posts from different users. Each post has a description, the name of the user, the time and an image (I use Picasso). Unfortunately when I start scrolling the view a very strong lag makes impossible to use the app.

I read many posts on the site but the only thing that helps me has been adding recyclerView.setItemViewCacheSize(20). However, the lag is still noticable. Here is my PostListActivity's code and layout (the activity where I put the recyclerview):

public class PostListActivity extends AppCompatActivity {

private FirebaseDatabase mDB;
private DatabaseReference mDBRef;
private FirebaseUser mUser;
private FirebaseAuth mAuth;
private RecyclerView recyclerView;
private BlogRecyclerAdapter blogRecyclerAdapter;
private List<Blog> blogList;
private DrawerLayout mDrawerLayout;
ExpandableListAdapter mMenuAdapter;
ExpandableListView expandableList;
List<ExpandedMenuModel> listDataHeader;
HashMap<ExpandedMenuModel, List<String>> listDataChild;


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

    final ActionBar ab = getSupportActionBar();





    BottomNavigationView bottomNavigationView = (BottomNavigationView)
            findViewById(R.id.bottom_navigation_view);

    bottomNavigationView.setOnNavigationItemSelectedListener(
            new BottomNavigationView.OnNavigationItemSelectedListener() {
                @Override
                public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                    switch (item.getItemId()) {
                        case R.id.action_PDFPOSTLIST:
                            if (mUser != null && mAuth != null){
                                startActivity(new Intent(PostListActivity.this, PDFPostListActivity.class));
                                finish();
                            }
                            break;

                    }
                    return false;
                }
            });





    /* to set the menu icon image*/
    ab.setHomeAsUpIndicator(android.R.drawable.ic_menu_sort_by_size);
    ab.setDisplayHomeAsUpEnabled(true);
    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawer_layout);
    expandableList = (ExpandableListView) findViewById(R.id.navigationmenu);
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);

    if (navigationView != null) {
        setupDrawerContent(navigationView);
    }

    prepareListData();
    mMenuAdapter = new ExpandableListAdapter(this, listDataHeader, listDataChild, expandableList);

    // setting list adapter
    expandableList.setAdapter(mMenuAdapter);

    expandableList.setOnChildClickListener(new ExpandableListView.OnChildClickListener() {
        @Override
        public boolean onChildClick(ExpandableListView expandableListView, View view, int groupPosition, int childPosition, long l) {
            //Log.d("DEBUG", "submenu item clicked");
            if (groupPosition == 3 && childPosition == 2) {
                startActivity(new Intent(PostListActivity.this, QuartaBUsersActivity.class));
            }
            return true;
        }
    });
    expandableList.setOnGroupClickListener(new ExpandableListView.OnGroupClickListener() {
        @Override
        public boolean onGroupClick(ExpandableListView expandableListView, View view, int i, long l) {
            //Log.d("DEBUG", "heading clicked");
            return false;
        }
    });

    //Recupero dell'istanza di autenticazione di Firebase
    mAuth = FirebaseAuth.getInstance();
    mUser = mAuth.getCurrentUser();

    /*
     * Recuperiamo l'istanza del database,
     * il riferimento alla posizione figlia in cui vogliamo memorizzare dati e
     * manteniamo il database sincronizzato tra dispositivo e cloud
     */
    mDB = FirebaseDatabase.getInstance();
    mDBRef = mDB.getReference().child("Blog");
    mDBRef.keepSynced(true);

    //Istanziamo la lista di post
    blogList = new ArrayList<>();
    //Istanziamo ed effettuiamo il setup della RecyclerView
    recyclerView = (RecyclerView) findViewById(R.id.RecyclerView4Post);
    recyclerView.setHasFixedSize(true);
    recyclerView.setItemViewCacheSize(20);
    recyclerView.setLayoutManager(new LinearLayoutManager(this));

    //Aggiungiamo un listener che monitori l'aggiunta di nuovi nodi figli nella posizione referenziata
    mDBRef.addChildEventListener(new ChildEventListener() {
        @Override
        public void onChildAdded(DataSnapshot dataSnapshot, String s) {
            /*
             * Questo metodo viene invocato quando vengono aggiunti nuovi nodi figli.
             */
            //Preleviamo il post dal database
            Blog post = dataSnapshot.getValue(Blog.class);
            //Aggiungiamo il post alla lista
            //   if (post.getUserID().equals(mUser.getUid()))

            blogList.add(post);
            //Invertiamo l'ordine la lista per visualizzare i nuovi post per primi
            Collections.reverse(blogList);
            //Istanziamo l'adapter
            blogRecyclerAdapter = new BlogRecyclerAdapter(PostListActivity.this, blogList);
            //Settiamo l'adapter sulla RecyclerView
            recyclerView.setAdapter(blogRecyclerAdapter);
            //Notifichiamo all'adapter che il dataset è cambiato
            blogRecyclerAdapter.notifyDataSetChanged();
        }
        @Override
        public void onChildChanged(DataSnapshot dataSnapshot, String s) {
            /*
             * Questo metodo viene invocato quando vengono modificati dati sul nodo figlio.
             */
        }
        @Override
        public void onChildRemoved(DataSnapshot dataSnapshot) {
            /*
             * Questo metodo viene invocato quando viene rimosso un nodo figlio.
             */
        }
        @Override
        public void onChildMoved(DataSnapshot dataSnapshot, String s) {
            /*
             * Questo metodo viene invocato quando cambia la priorità della posizione dei nodi figli.
             */
        }
        @Override
        public void onCancelled(DatabaseError databaseError) {
            /*
             * Questo metodo viene invocato quando non è stato possibile reperire il dato.
             */
        }
    });


}


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

private void prepareListData() {
    listDataHeader = new ArrayList<ExpandedMenuModel>();
    listDataChild = new HashMap<ExpandedMenuModel, List<String>>();

    ExpandedMenuModel item1 = new ExpandedMenuModel();
    item1.setIconName("Prime Liceo");
    item1.setIconImg(android.R.drawable.ic_menu_more);
    // Adding data header
    listDataHeader.add(item1);

    ExpandedMenuModel item2 = new ExpandedMenuModel();
    item2.setIconName("Seconde Liceo");
    item2.setIconImg(android.R.drawable.ic_menu_more);
    listDataHeader.add(item2);

    ExpandedMenuModel item3 = new ExpandedMenuModel();
    item3.setIconName("Terze Liceo");
    item3.setIconImg(android.R.drawable.ic_menu_more);
    // Adding data header
    listDataHeader.add(item3);

    ExpandedMenuModel item4 = new ExpandedMenuModel();
    item4.setIconName("Quarte Liceo");
    item4.setIconImg(android.R.drawable.ic_menu_more);
    // Adding data header
    listDataHeader.add(item4);

    ExpandedMenuModel item5 = new ExpandedMenuModel();
    item5.setIconName("PROF");
    item5.setIconImg(android.R.drawable.star_big_on);
    // Adding data header
    listDataHeader.add(item5);

    // Adding child data
    List<String> heading1 = new ArrayList<String>();
    heading1.add("1A                                   ");
    heading1.add("IA                                   ");
    heading1.add("1B                                   ");
    heading1.add("IB                                   ");

    List<String> heading2 = new ArrayList<String>();
    heading2.add("2A                                   ");
    heading2.add("IIA                                  ");
    heading2.add("2B                                   ");
    heading2.add("IIB                                  ");

    List<String> heading3 = new ArrayList<String>();
    heading3.add("3A                                    ");
    heading3.add("IIIA                                  ");
    heading3.add("3B                                    ");
    heading3.add("IIIB                                  ");

    List<String> heading4 = new ArrayList<String>();
    heading4.add("4A                                    ");
    heading4.add("IVA                                   ");
    heading4.add("4B                                    ");
    heading4.add("IVB                                   ");

    listDataChild.put(listDataHeader.get(0), heading1);// Header, Child data
    listDataChild.put(listDataHeader.get(1), heading2);
    listDataChild.put(listDataHeader.get(2), heading3);
    listDataChild.put(listDataHeader.get(3), heading4);

}


//Metodo chiamato dalla piattaforma per la creazione del menù
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    //Recupero dell'inflater e inflate del layout predisposto
    getMenuInflater().inflate(R.menu.main_menu, menu);
    return super.onCreateOptionsMenu(menu);
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
        case android.R.id.home:
            mDrawerLayout.openDrawer(GravityCompat.START);
            return true;

            case R.id.action_addPDF:
            /*
             * Quando l'utente sceglie l'item per aggiungere un nuovo post
             * lo direzioniamo verso l'activity appropriata
             */
            if (mUser != null && mAuth != null){
                startActivity(new Intent(PostListActivity.this, AddPDFActivity.class ));
            }
            break;

            case R.id.action_addPHOTO:
            /*
             * Quando l'utente sceglie l'item per aggiungere un nuovo post
             * lo direzioniamo verso l'activity appropriata
             */
            if (mUser != null && mAuth != null){
                startActivity(new Intent(PostListActivity.this, AddPostActivity.class ));
            }
            break;

            case R.id.action_signout:
            /*
             * Quando l'utente sceglie l'item per effettuare il logout
             * eseguiamo l'operazione e ritorniamo all'activity di login e registrazione
             */
            if (mAuth != null){
                mAuth.signOut();
                Toast.makeText(PostListActivity.this, "Utente disconnesso", Toast.LENGTH_SHORT).show();
                startActivity(new Intent(PostListActivity.this, MainActivity.class));
                finish();
            }
            break;

            case R.id.action_myphoto:
                if (mUser != null && mAuth != null) {
                    startActivity(new Intent(PostListActivity.this, MyPostListActivity.class));
                }
                break;

            case R.id.action_mypdf:
                if (mUser != null && mAuth != null) {
                    startActivity(new Intent(PostListActivity.this, MyPDFPostListActivity.class));
                }
                break;

        case R.id.action_changeprofileimage:
            if (mUser != null && mAuth != null) {
                startActivity(new Intent(PostListActivity.this, ChangeProfileImageActivity.class));
            }
            break;




    }
    return super.onOptionsItemSelected(item);
}

private void setupDrawerContent(NavigationView navigationView) {
    //revision: this don't works, use setOnChildClickListener() and setOnGroupClickListener() above instead
    navigationView.setNavigationItemSelectedListener(
            new NavigationView.OnNavigationItemSelectedListener() {
                @Override
                public boolean onNavigationItemSelected(MenuItem menuItem) {
                    menuItem.setChecked(true);
                    mDrawerLayout.closeDrawers();
                    return true;
                }
            });
}


@Override
public void onBackPressed() {
    DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
    if (drawer.isDrawerOpen(GravityCompat.START)) {
        drawer.closeDrawer(GravityCompat.START);
    } else {
        super.onBackPressed();
    }
}




}

And here is the layout:

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

<androidx.drawerlayout.widget.DrawerLayout android:id="@+id/drawer_layout"
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="match_parent"
android:fitsSystemWindows="true"
xmlns:design="http://schemas.android.com/tools">




<LinearLayout 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"
tools:context=".PostListActivity">

    <androidx.recyclerview.widget.RecyclerView
        android:id="@+id/RecyclerView4Post"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginBottom="?actionBarSize" />




</LinearLayout>


<include layout="@layout/bottom_navigation_layout" />

<com.google.android.material.navigation.NavigationView
    android:id="@+id/nav_view"
    android:layout_width="wrap_content"
    android:layout_height="match_parent"
    android:layout_gravity="start"
    android:fitsSystemWindows="true"
    app:headerLayout="@layout/nav_header_main"
    >

    <ExpandableListView
        android:id="@+id/navigationmenu"
        android:layout_width="wrap_content"
        android:layout_height="match_parent"
        android:layout_marginTop="192dp"
        android:groupIndicator="@android:color/transparent"
        android:background="@android:color/white"
        >
    </ExpandableListView>

</com.google.android.material.navigation.NavigationView>

I also thought that the Adapter used for the recycler may be useful to understand the problem

public class BlogRecyclerAdapter extends RecyclerView.Adapter<BlogRecyclerAdapter.ViewHolder> {
private Context context;
private List<Blog> blogList;
public BlogRecyclerAdapter(Context context, List<Blog> blogList) {
    this.context = context;
    this.blogList = blogList;
}
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    View view = LayoutInflater.from(parent.getContext())
            .inflate(R.layout.post_row, parent, false);
    return new ViewHolder(view, context);
}
@Override
public void onBindViewHolder(final ViewHolder holder, int position) {
    Blog blog = blogList.get(position);
    holder.nameUser.setText(blog.getNameUser());
    holder.surnameUser.setText(blog.getSurnameUser());
    holder.classUser.setText(blog.getClassUser());
    holder.description.setText(blog.getDescription());
    DateFormat dateFormat = DateFormat.getDateInstance();
    String formattedDate = dateFormat.format(new Date(Long.valueOf(blog.getTimeStamp())).getTime());
    holder.timeStamp.setText(formattedDate);
    final String imageURL = blog.getImage();
    Picasso.get().load(imageURL).into(holder.image);



}
@Override
public int getItemCount() {
    return blogList.size();
}
public class ViewHolder extends RecyclerView.ViewHolder {
    private ImageView image;
    private TextView nameUser;
    private TextView surnameUser;
    private TextView classUser;
    private TextView description;
    private TextView timeStamp;
    private String userID;
    public ViewHolder(View itemView, Context ctx) {
        super(itemView);
        image = (ImageView) itemView.findViewById(R.id.postImageList);
        nameUser = (TextView)itemView.findViewById(R.id.textViewNAME);
        surnameUser = (TextView)itemView.findViewById(R.id.textViewSURNAME);
        classUser = (TextView)itemView.findViewById(R.id.textViewCLASS);
        description = (TextView) itemView.findViewById(R.id.postTextList);
        timeStamp = (TextView) itemView.findViewById(R.id.timeStampList);
        userID = null;

    }
}
}

Answer 1

Use Glide library and try to reduce the image file size. This will reduce/remove the lag u face on your device