如何为新项目添加 RecyclerView 滑入动画

Question

I have a RecyclerView and add items to mCommentArrayList at index 0. I am trying to create a slide-in animation at the top of the view as new items (CardViews) are added to the RecyclerView.

I know there are libraries that can be used, and I have even explored https://github.com/wasabeef/recyclerview-animators . However, the documentation is limited and I am unsure what approach to take.

Note that I add all new items to my mCommentArrayList at index 0 so that they appear at the top of the view. I know there is some work to be done in the adapter, specifically onBindViewHolder() , but I don't know exactly what to put in order to activate the animations.

Where I first call to Firebase to find data to populate the RecyclerView:

    mUpdateRef.addListenerForSingleValueEvent(new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            setImage(dataSnapshot);
            setQuestion(dataSnapshot);
            createInitialCommentIDArray(dataSnapshot);
            mNumberOfCommentsAtPoll = (int) dataSnapshot.child(COMMENTS_LABEL).getChildrenCount();
            for (int i = 0; i < mNumberOfCommentsAtPoll; i++) {
                String commentID = (String) dataSnapshot.child(COMMENTS_LABEL).child(mCommentIDArrayList.get(i)).child("COMMENT").getValue();
                Log.v("COMMENT_ID", "The comment ID is " + commentID);
                String userID = (String) dataSnapshot.child(COMMENTS_LABEL).child(mCommentIDArrayList.get(i)).child("USER_ID").getValue();
                Log.v("USER_ID", "The user ID is " + userID);
                mCommentArrayList.add(0, new Comments(mUserAvatar, userID, commentID));
                mCommentAdapter.notifyDataSetChanged();
            }

        }

        @Override
        public void onCancelled(FirebaseError firebaseError) {

        }
    });

Subsequent Calls to Firebase on Data Change:

@Override
protected void onStart() {
    super.onStart();
    mUpdateComments = new ValueEventListener() {
        @Override
        public void onDataChange(DataSnapshot dataSnapshot) {
            mNumberOfCommentsAtPoll = (int) dataSnapshot.getChildrenCount();
            for (DataSnapshot x : dataSnapshot.child(COMMENTS_LABEL).getChildren()) {
                Log.v("DATA_SNAPSHOT", x.toString());
                if (mCommentIDArrayList.contains(x.getKey())) {
                    Log.v("Comment_Already_Added", x.getKey());
                } else {
                    Log.v("Child_Added_Called", "Child Added Called");
                    mCommentIDArrayList.add(x.getKey());
                    String commentID = (String) dataSnapshot.child(COMMENTS_LABEL).child(x.getKey()).child("COMMENT").getValue();
                    Log.v("New_Comment", "The new comment is " + commentID);
                    String userID = (String) dataSnapshot.child(COMMENTS_LABEL).child(x.getKey()).child("USER_ID").getValue();
                    Log.v("New_User_ID", "The new userID is " + userID);
                    mCommentArrayList.add(0, new Comments(mUserAvatar, userID, commentID));
                    mPollCommentsList.getAdapter().notifyItemInserted(0);
                }
            }
        }

Answer 1

Using the library you were talking about ( https://github.com/wasabeef/recyclerview-animators ) it's very easy to add a SlideInAnimator to your RecyclerView . Just use the following code to set an Animator to your RecyclerView (pick one):

    recyclerView.setItemAnimator(new SlideInDownAnimator());
    recyclerView.setItemAnimator(new SlideInRightAnimator());
    recyclerView.setItemAnimator(new SlideInLeftAnimator());
    recyclerView.setItemAnimator(new SlideInUpAnimator());

Once you have done this the you can simply trigger the animation by calling notifyItemInserted(position) or notifyItemRangeInserted(positionStart, itemCount) . These calls will trigger the Animator , calling notifyDatasetChanged() won't .

Triggering the insertion animation:

    recyclerView.getAdapter().notifyItemInserted(position);
    recyclerView.getAdapter().notifyItemRangeInserted(positionStart, itemCount);

Answer 2

Hope this code help's you !

create one animation file animation_from_right.xml

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

<set xmlns:android="http://schemas.android.com/apk/res/android"
android:duration="700"
android:fillAfter="false"
>

<translate
android:interpolator="@android:anim/decelerate_interpolator"
android:fromXDelta="100%p"
android:toXDelta="0"
/>

<alpha
android:fromAlpha="0.5"
android:toAlpha="1"
android:interpolator="@android:anim/accelerate_decelerate_interpolator"
/>

</set>

in Activity

Animation animation = AnimationUtils.loadAnimation(mActivity, R.anim.animation_from_right);
        holder.itemView.startAnimation(animation);

use above code in your Adapter on onBindViewHolder

Answer 3

The best way animate the recyclerview will be to do it in the onbindviewholder method .

Here is how to do it-

create a field variable lastAnimatedPosition in the adapter class.

private int lastAnimatedPosition = -1;

Then in the onbindviewholder-

 @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        Comments comment = mDataSet.get(position);
        holder.userComment.setText(comment.getUserComment());
        holder.userID.setText("User " + position);
if (position > lastAnimatedPosition) {
      lastAnimatedPosition = position;
      Animation animation = AnimationUtils.loadAnimation(context, R.anim.my_anim_set);
      animation.setInterpolator(new AccelerateDecelerateInterpolator());
      ((ViewHolder) holder).container.setAnimation(animation);
      animation.start();
    }
    }

Next a few tweaks in your viewholder class-

public class ViewHolder extends RecyclerView.ViewHolder {
        // each data item is just a string in this case
        protected ImageView userAvatar;
        protected TextView userID;
        protected TextView userComment;
        **protected View container;**


        public ViewHolder(View v) {
            super(v);
            **container = v;**
            userAvatar = (ImageView) v.findViewById(R.id.profile_image);
            userID = (TextView) v.findViewById(R.id.user_ID);
            userComment = (TextView) v.findViewById(R.id.user_comment_textview);
        }

        **public void clearAnimation() {
          container.clearAnimation();
        }**
    }

And lastly simply override onViewDetachedFromWindow -

@Override
  public void onViewDetachedFromWindow(final ViewHolder holder) {
    holder.clearAnimation();
  }

UPDATE

Since the element to be animated is in the 0th index replace the if (position > lastAnimatedPosition) snippet with -

if (position == 0) {
      lastAnimatedPosition = position;
      Animation animation = AnimationUtils.loadAnimation(context, R.anim.my_anim_set);
      animation.setInterpolator(new AccelerateDecelerateInterpolator());
      ((ViewHolder) holder).container.setAnimation(animation);
      animation.start();
    }