I have a RecyclerView implementation inside of a ViewPager, and its performance is pretty horrible. I have two view types, and am using the ViewHolder pattern (so it's not inflation or finding views causing the issue).
Here's the cardview.xml file
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:clipChildren="false"
android:orientation="vertical"
android:scrollbars="none">
<LinearLayout
android:id="@+id/next"
android:layout_width="match_parent"
android:layout_height="2dp"
android:layout_marginBottom="8dp"
android:elevation="8dp"
android:orientation="horizontal" />
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/top"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="?attr/card_background"
android:orientation="horizontal">
<LinearLayout
android:id="@+id/dots"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentBottom="true"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:background="?attr/activity_background"
android:orientation="horizontal">
</LinearLayout>
<View
android:id="@+id/dot"
android:layout_width="3dp"
android:layout_height="match_parent"
android:layout_alignParentBottom="true"
android:layout_alignParentTop="true"
android:layout_toRightOf="@id/dots"
android:background="#fff" />
<RelativeLayout
android:id="@+id/background"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_toRightOf="@+id/dot"
android:orientation="vertical"
android:paddingLeft="8dp"
android:paddingRight="8dp"
android:paddingTop="8dp">
<include
android:id="@+id/children"
layout="@layout/commentnumber"
android:layout_width="wrap_content"
android:layout_height="16dp"
android:layout_alignParentRight="true"
android:layout_gravity="right"
android:layout_marginBottom="-16dp"
android:layout_marginLeft="10dp"
android:gravity="center_horizontal"
android:orientation="horizontal" />
<com.wefika.flowlayout.FlowLayout
android:id="@+id/flow"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_gravity="center_vertical"
android:gravity="center_vertical"
android:orientation="horizontal"
android:paddingRight="10dp">
<TextView
android:id="@+id/author"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:layout_gravity="center_vertical"
android:paddingRight="5dp"
android:text="ccrama"
android:textColor="?attr/font"
android:textSize="?attr/font_commenttitle"
android:textStyle="bold"
/>
<TextView
android:id="@+id/score"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:layout_gravity="center_vertical"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:text="+49"
android:textColor="?attr/font"
android:textSize="?attr/font_commentinfo"
android:textStyle="bold" />
<TextView
android:id="@+id/time"
android:layout_width="wrap_content"
android:layout_height="match_parent"
android:gravity="center_vertical"
android:layout_alignParentRight="true"
android:layout_gravity="center_vertical"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:text="4 hours ago"
android:textColor="?attr/font"
android:textSize="?attr/font_commentinfo" />
<include
android:id="@+id/gild"
layout="@layout/gilded"
android:layout_width="wrap_content"
android:layout_height="16dp"
android:layout_gravity="center_vertical"
android:gravity="center_horizontal"
android:orientation="horizontal"
android:paddingLeft="5dp"
android:paddingRight="5dp" />
<include
android:id="@+id/flairbubble"
layout="@layout/flair"
android:layout_width="wrap_content"
android:layout_height="16dp"
android:layout_gravity="center_vertical"
android:layout_margin="5dp"
android:layout_toRightOf="@+id/pinned"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:src="@drawable/pinned" />
<include
android:id="@+id/you"
layout="@layout/you"
android:layout_width="wrap_content"
android:layout_height="16dp"
android:layout_centerVertical="true"
android:layout_gravity="center_vertical"
android:layout_toRightOf="@+id/pinned"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:src="@drawable/pinned" />
<include
android:id="@+id/op"
layout="@layout/op"
android:layout_width="wrap_content"
android:layout_height="16dp"
android:layout_marginLeft="4dp"
android:layout_centerVertical="true"
android:layout_gravity="center_vertical"
android:layout_toRightOf="@+id/pinned"
android:paddingLeft="5dp"
android:paddingRight="5dp"
android:src="@drawable/pinned" />
</com.wefika.flowlayout.FlowLayout>
<me.ccrama.redditslide.ActiveTextView
android:id="@+id/content"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/flow"
android:paddingBottom="8dp"
android:textColor="?attr/font"
android:textSize="?attr/font_commentbody" />
</RelativeLayout>
</LinearLayout>
<LinearLayout
android:id="@+id/menu"
android:layout_width="match_parent"
android:layout_height="48dp"
android:layout_below="@+id/background"
android:orientation="horizontal"
android:weightSum="4">
<ImageView
android:id="@+id/more"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:background="?android:selectableItemBackground"
android:padding="12dp"
android:src="@drawable/more"
android:tint="?attr/tint" />
<ImageView
android:id="@+id/downvote"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:background="?android:selectableItemBackground"
android:padding="12dp"
android:src="@drawable/downvoteicon"
android:tint="?attr/tint" />
<ImageView
android:id="@+id/upvote"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:background="?android:selectableItemBackground"
android:padding="12dp"
android:src="@drawable/upvoteicon"
android:tint="?attr/tint" />
<ImageView
android:id="@+id/reply"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:background="?android:selectableItemBackground"
android:padding="12dp"
android:src="@drawable/reply"
android:tint="?attr/tint" />
</LinearLayout>
<LinearLayout
android:id="@+id/replyArea"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_below="@+id/menu"
android:orientation="vertical"
android:padding="16dp">
<EditText
android:id="@+id/replyLine"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:backgroundTint="?attr/tint"
android:hint="Reply"
android:imeOptions="actionDone|flagNoEnterAction"
android:inputType="textMultiLine|textAutoCorrect|textCapSentences"
android:minHeight="30dp"
android:textColor="?attr/font"
android:textColorHint="?attr/font" />
<RelativeLayout
android:layout_width="match_parent"
android:layout_height="wrap_content">
<TextView
android:id="@+id/discard"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:background="?android:selectableItemBackground"
android:padding="4dp"
android:text="DISCARD"
android:textColor="?attr/font"
android:textSize="14sp"
android:textStyle="bold" />
<TextView
android:id="@+id/send"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:background="?android:selectableItemBackground"
android:padding="4dp"
android:text="SUBMIT"
android:textColor="?attr/font"
android:textSize="14sp"
android:textStyle="bold" />
</RelativeLayout>
<LinearLayout
android:id="@+id/innersend2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_gravity="center"
android:layout_marginLeft="-6dp"
android:layout_marginRight="-6dp"
android:alpha=".56"
android:gravity="center"
android:orientation="horizontal"
android:weightSum="8">
<ImageButton
android:id="@+id/imagerep"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/image"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/link"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/link"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/bold"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/bold"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/italics"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/italics"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/bulletlist"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/bullets"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/numlist"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/numbers"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/quote"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/quotes"
android:tint="?attr/tint" />
<ImageButton
android:id="@+id/size"
android:layout_width="0dp"
android:layout_height="48dp"
android:layout_weight="1"
android:height="48dp"
android:background="#00000000"
android:cropToPadding="false"
android:padding="8dp"
android:scaleType="fitCenter"
android:src="@drawable/fontsizedarker"
android:tint="?attr/tint" />
</LinearLayout>
</LinearLayout>
Removing all the adapter code except for inflation still results in noticeable lag. I really can't find the bottom of this, and any help/tips are greatly appreciated.
Some more information: Removing the dataset "hiding" code (getRealPosition, hideAll, unhideAll) has no affect on the speed of the RecyclerView. Also, removing the FlowLayout does not make it any faster.
I was having the same problem with RecyclerView. It was laggy. In my case, there was a horizontal list of image buttons inside RecyclerView.
I solved it by removing the scaleType from ImageButtons or ImageViews and loading images through Picasso with resizing like :
Picasso.with(context).load(icon.get(position)).resize(270,270).centerCrop().into(holder.iconView);
The problem of lag may occur due to runtime scaling of big sized images or no. of images. It is not advisable. Whereas Picasso takes care of resizing, and loading efficiently. Also it handles caching for you.