ItemAnimator.java

package net.aquadc.commonandroid.lists;

import android.support.v4.view.ViewCompat;
import android.support.v4.view.ViewPropertyAnimatorCompat;
import android.support.v7.widget.RecyclerView;
import android.view.View;
import com.mikepenz.itemanimators.DefaultAnimator;

/**
 * ItemAnimator implementation which animates items so it looks like they're falling into list.
 * Forked from <a href="https://gist.github.com/enq3/2dae8e769e9606349b22fdbdf65c41a1">enq3's animator</a>.
 * Extends DefaultAnimator written by Mike Penz and available at
 * <a href="https://github.com/mikepenz/ItemAnimators/blob/develop/library/src/main/java/com/mikepenz/itemanimators/DefaultAnimator.java}">his GitHub repo</a>.
 *
 * Sample usage: {@code recycler.setItemAnimator(new ItemAnimator().withPageSize(10).withInterpolator(new DecelerateInterpolator(.7f)).withAddDuration(300))}
 */
public class ItemAnimator extends DefaultAnimator<ItemAnimator> {

    /**
     * I don't know why on earth you may need to disable animation, I'll just leave it here.
     */
    private boolean useAnimation = true;

    private int durationPerOffset = 50;
    private int delayPerOffset = 25;

    private int pageSize = Integer.MAX_VALUE;


    public boolean isUseAnimation() { return useAnimation; }
    public int getDurationPerOffset() { return durationPerOffset; }
    public int getDelayPerOffset() { return delayPerOffset; }
    public int getPageSize() { return pageSize; }


    public ItemAnimator withAnimation(boolean useAnimation) {
        this.useAnimation = useAnimation;
        return this;
    }
    public ItemAnimator withAnimationParametersPerOffset(int durationPerOffset, int delayPerOffset) {
        this.durationPerOffset = durationPerOffset;
        this.delayPerOffset = delayPerOffset;
        return this;
    }
    /**
     * When you're loading items in pages, next page will be animated slower without this correction.
     * To turn off this correction, set to {@link Integer.MAX_VALUE}
     */
    public ItemAnimator withPageSize(int pageSize) {
        this.pageSize = pageSize;
        return this;
    }

    /**
     * Just proxies your value to {@link this#setAddDuration} and returns itself.
     */
    public ItemAnimator withAddDuration(int addDuration) {
        setAddDuration(addDuration);
        return this;
    }


    @Override public void addAnimationPrepare(RecyclerView.ViewHolder holder) {
        if (useAnimation) {
            ViewCompat.setTranslationY(holder.itemView, holder.itemView.getHeight() * 0.4f);
            ViewCompat.setAlpha(holder.itemView, 0.0f);
        }
    }

    @Override public ViewPropertyAnimatorCompat addAnimation(final RecyclerView.ViewHolder holder) {
        holder.itemView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
        int off = holder.getAdapterPosition() < 0 ? holder.getLayoutPosition() : holder.getAdapterPosition();
        while (off >= pageSize) off -= pageSize;
        return ViewCompat.animate(holder.itemView)
                .alpha(1)
                .translationY(0)
                .setDuration(useAnimation ? getAddDuration() + durationPerOffset * off : 0)
                .setInterpolator(getInterpolator())
                .setStartDelay(useAnimation ? off * delayPerOffset : 0);
    }

    @Override public void addAnimationCleanup(RecyclerView.ViewHolder holder) {
        ViewCompat.setAlpha(holder.itemView, 1);
        ViewCompat.setTranslationY(holder.itemView, 0);
    }

    @Override public ViewPropertyAnimatorCompat removeAnimation(final RecyclerView.ViewHolder holder) {
        holder.itemView.setLayerType(View.LAYER_TYPE_HARDWARE, null);
        return ViewCompat.animate(holder.itemView)
                .alpha(0)
                .setDuration(useAnimation ? getRemoveDuration() : 0)
                .setInterpolator(getInterpolator())
                .setStartDelay(0);
    }

    @Override public void removeAnimationCleanup(RecyclerView.ViewHolder holder) {
        ViewCompat.setAlpha(holder.itemView, 1);
    }

    @Override public ViewPropertyAnimatorCompat changeOldAnimation(RecyclerView.ViewHolder holder, ChangeInfo changeInfo) {
        return ViewCompat.animate(holder.itemView)
                .setDuration(getChangeDuration())
                .alpha(0)
                .translationX(changeInfo.toX - changeInfo.fromX)
                .translationY(changeInfo.toY - changeInfo.fromY)
                .setInterpolator(getInterpolator());
    }

    @Override public ViewPropertyAnimatorCompat changeNewAnimation(RecyclerView.ViewHolder holder) {
        return ViewCompat.animate(holder.itemView)
                .translationX(0)
                .translationY(0)
                .setDuration(getChangeDuration())
                .alpha(1)
                .setInterpolator(getInterpolator());
    }

    @Override public void changeAnimationCleanup(RecyclerView.ViewHolder holder) {
        ViewCompat.setAlpha(holder.itemView, 1);
    }
}