MainActivity RecyclerView lags

Question

My app, particularly the MainActivity suffers from some lag when I scroll through the RecyclerView. I tried to fix OverDraw as much as I can.

This is what my OverDraw screenshot looks like:

OverDraw

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout 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"
xmlns:ads="http://schemas.android.com/apk/res-auto"
android:background="@drawable/background"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".ChordsList.ChordsListActivity">
<RelativeLayout
 android:id="@+id/layout_top"
 android:layout_width="match_parent"
 android:layout_height="wrap_content">
 <ImageView
 android:id="@+id/logo"
 android:layout_width="match_parent"
 android:layout_height="100dp"
 android:scaleType="fitStart"
 android:src="@drawable/icon_verde_acqua_tras"/>
 <ImageButton
 android:id="@+id/menu"
 android:background="@color/trans"
 android:layout_width="40dp"
 android:layout_height="40dp"
 android:src="@drawable/tasto_menu"
 android:scaleType="fitCenter"
 android:layout_centerVertical="true"
 android:layout_alignParentEnd="true"
 android:layout_marginTop="20dp"
 android:onClick="showMenu"/>
 <ImageButton
 android:id="@+id/search"
 android:background="@color/trans"
 android:layout_width="40dp"
 android:layout_height="40dp"
 android:src="@drawable/tasto_ricerca"
 android:scaleType="fitCenter"
 android:layout_centerVertical="true"
 android:onClick="onSearchButtonPressed"
 android:layout_toStartOf="@id/menu"
 android:layout_marginTop="20dp" />
 <ImageButton
 android:id="@+id/tuner"
 android:background="@color/trans"
 android:layout_width="40dp"
 android:layout_height="40dp"
 android:layout_centerVertical="true"
 android:onClick="onTunerButtonPressed"
 android:src="@drawable/tuner"
 android:scaleType="fitCenter"
 android:layout_toStartOf="@id/search"
 android:layout_marginTop="20dp" />
</RelativeLayout>
<android.support.v7.widget.RecyclerView
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:id="@+id/chords_recycler"
 android:layout_below="@+id/layout_top"
 android:layout_alignParentStart="true"
 android:layout_marginTop="25dp" />
</RelativeLayout>

row.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent" android:layout_height="wrap_content">
<TextView
 android:id="@+id/nome"
 android:layout_width="wrap_content"
 android:layout_height="wrap_content"
 android:textAllCaps="true"
 android:layout_centerVertical="true"
 android:textSize="25sp"
 android:layout_marginTop="10dp"
 android:fontFamily="sans-serif-condensed"
 android:textStyle="bold"
 android:textColor="@color/black" />
<ImageView
 android:id="@+id/immagine_accordo"
 android:layout_width="130dp"
 android:layout_marginTop="5dp"
 android:layout_height="100dp"
 android:scaleType="fitCenter"
 android:layout_alignParentEnd="true"/>
</RelativeLayout>

Assuming that the problem is OverDraw (please tell me if it's not), how can I improve it further? I need everything that is in the Image, so I cannot remove the background.

As suggested by Ivanhoe, OverDraw does not seem to be a problem. The Adapter class and binding could be.

Adapter class:

public class ChordsListAdapter extends RecyclerView.Adapter<ChordsListAdapter.MyViewHolder> {
private ArrayList<Accordo> chordsList;
Context c;
public class MyViewHolder extends RecyclerView.ViewHolder {
 public TextView nome; //note
 public ImageView immagine;
 public MyViewHolder(View view) {
 super(view);
 nome = (TextView) view.findViewById(R.id.nome);
 immagine = (ImageView) view.findViewById(R.id.immagine_accordo);
 }
}
public ChordsListAdapter(Context c, ArrayList<Accordo> chordsList) {
 this.chordsList = chordsList;
 this.c = c;
}
@Override
public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
 View itemView = LayoutInflater.from(parent.getContext()).inflate(R.layout.row, parent, false);
 return new MyViewHolder(itemView);
}
@Override
public void onBindViewHolder(MyViewHolder holder, int position) {
 Accordo chord = chordsList.get(position);
 holder.nome.setText(chord.getName());
 holder.immagine.setImageResource(chord.getImage()[0]);
}
@Override
public int getItemCount() {
 return chordsList.size();
}
}

• Mast: Taking for granted that the problem is OverDraw How do you know?
• Daniele: I don't know, that's why I added "please tell me if it's not" :)
• Ivanhoe: I don't see any red in your overdraw snapshot so that's not why your list is laggy.
• Ivanhoe: Could you provide your adapter's implementation? I suspect the problem might be in your "binding" code.
• Daniele: @Ivanhoe I have updated my question with the adapter class

Answer 1

You're instantiating MyViewHolder for every binding, that means you're executing findViewById for each item which is an expensive method. A solution would be to cache the created instance of MyViewHolder in onCreateViewHolder by assigning it to the view tag, and reuse it. Have a look a this https://developer.android.com/training/improving-layouts/smooth-scrolling.html

• Ivanhoe: This is true for a regular ListView implementation. The OP is using RecyclerView where this overhead is already taken care of. onCreateViewHolder() will only be called when it is needed developer.android.com/reference/android/support/v7/widget/… android.view.ViewGroup, int