Unknown animation name: decelerateInterpolator

Question

Android Studio 1.5
Device Samsung 4.4.2

I am trying to animate items loaded from a ArrayList into a recyclerview. I when the dropdown arrow is clicked the items should animate (decelerate) when expanded and should animate when collapsed. However, currently the list items just appears.

Code that calls the setAnimation

 @Override
    public void onBindChildViewHolder(ChatChildViewHolder childViewHolder, int position, Object childListItem) {
        ChatChildTitles chatChildTitles = (ChatChildTitles)childListItem;
        childViewHolder.tvChildTitle.setText(chatChildTitles.getTitle());

        setAnimation(childViewHolder.cvChildRooms, position);
    }

Code for setting the animation

  private void setAnimation(CardView viewToAnimate, int position) {
        Animation animation = AnimationUtils.loadAnimation(mContext, android.R.anim.fade_in);
        animation.setInterpolator(mContext, android.R.anim.decelerate_interpolator);
        viewToAnimate.startAnimation(animation);
    }

Here is a couple of screenshots:

In the collapsed state

After the arrow has been clicked expland the list

This is my layout I am using that represents the rows that will be displayed in the recyclerView:

<?xml version="1.0" encoding="utf-8"?>
<android.support.v7.widget.CardView
    android:id="@+id/cvChildRooms"
    xmlns:card="http://schemas.android.com/apk/res-auto"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    card:cardBackgroundColor="@color/child_header_lighter_grey"
    card:contentPadding="4dp"
    card:cardPreventCornerOverlap="true">

    <de.hdodenhof.circleimageview.CircleImageView
        android:id="@+id/profile_image"
        android:layout_width="40dp"
        android:layout_height="40dp"
        android:layout_gravity="center_vertical|start"
        android:src="@drawable/photorace"/>

    <TextView
        android:id="@+id/tvChildTitle"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical|center"
        android:text="Coffee Latte Room"
        android:fontFamily="sans-serif-light"
        android:textSize="16sp"
        android:textColor="@android:color/black"/>
</android.support.v7.widget.CardView>

I have a function that should start the animation.

private void setAnimation(CardView viewToAnimate, int position) {
    Animation animation = AnimationUtils.loadAnimation(mContext, android.R.anim.decelerate_interpolator);
    viewToAnimate.startAnimation(animation);
}

I have tested using the following that works ok with slide_in_left. However, I don't want them to slide in from the left

Animation animation = AnimationUtils.loadAnimation(mContext, android.R.anim.slide_in_left);
viewToAnimate.startAnimation(animation);

Many thanks for any suggestions,

Answer 1

If you want to use a decelerate interpolator you need to set it AS an interpolator, not as the animator:

private void setAnimation(CardView viewToAnimate, int position) {
    Animation animation = AnimationUtils.loadAnimation(mContext, android.R.anim.fade_in); //change this with your desidered (or custom) animation
    animation.setInterpolator(mContext, android.R.anim.decelerate_interpolator);
    viewToAnimate.startAnimation(animation);
}

---

UPDATE

You said that you are using com.bignerdranch.android:expandablerecyclerview:2.0.3.

From the official docs of the library, it's clearly state how to create expand/collapse animations:

You can also create your own animations for expansion by overriding ParentViewHolder#onExpansionToggled(boolean), which will be called for you when the itemView is expanded or collapsed.

I suggest you to take a look at the official example of the library.

Answer 2

You can't use decelerate_interpolator because it's not an animation, it is an interpolator:

An interpolator defines the rate of change of an animation. This allows the basic animation effects (alpha, scale, translate, rotate) to be accelerated, decelerated, repeated, etc.

Reference:
http://developer.android.com/reference/android/view/animation/Interpolator.html

As you can see the XML that describing them are completely different:

Source of decelerate_interpolator.xml:

<decelerateInterpolator />

Source of slide_in_left.xml:

<set xmlns:android="http://schemas.android.com/apk/res/android">
    <translate android:fromXDelta="-50%p" android:toXDelta="0"
            android:duration="@android:integer/config_mediumAnimTime"/>
    <alpha android:fromAlpha="0.0" android:toAlpha="1.0"
            android:duration="@android:integer/config_mediumAnimTime" />
</set>