调用notifydatasetchanged（）之后，在Recyclerview中保持视图状态不变

Question

I have a recycler adapter which has 3 itemviewtypes. No.1 type of view has an initial animation to show the view which I've written under the holder instance check in the OnBindView . it works fine. but when there is any change in the other view types, notifydatasetchanged() is called and the adapter is set again which makes the animation start again. i tried putting a flag for the animation where it would only animate the first time. is there a smarter way to do this?

    public RecyclerView.ViewHolder onCreateViewHolder(ViewGroup parent, int 
    viewType) {

mSharedPreferencesManager.setVersionNewFeatureCheck(BuildConfig.VERSION_NAME);

    Logger.i(TAG, "onCreateViewHolder, " + viewType);

    if (viewType == TYPE_HEADER) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.converation_header_row, parent, false);
        return new HeaderViewHolder(v);
    } else if(viewType == TYPE_ANNOUNCEMENT) {
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.chat_new_feature_notification, parent, false);
        return new FeatureNotificationViewHolder(v);
    }
        else{
        View v = LayoutInflater.from(parent.getContext()).inflate(R.layout.conversation_row, parent, false);
        return new ConversationRowViewHolder(v);
    }
}

f (holder instanceof FeatureNotificationViewHolder) { final FeatureNotificationViewHolder featureNotificationViewHolder = (FeatureNotificationViewHolder) holder;

                featureNotificationViewHolder.chatNewFeatureNotif.getViewTreeObserver().addOnPreDrawListener(new ViewTreeObserver.OnPreDrawListener() {
                    @Override
                    public boolean onPreDraw() {

                        final int height = featureNotificationViewHolder.chatNewFeatureNotif.getMeasuredHeight();
                        featureNotificationViewHolder.chatNewFeatureNotif.setVisibility(View.GONE);
                        featureNotificationViewHolder.chatNewFeatureNotif.getViewTreeObserver().removeOnPreDrawListener(this);
                        mOverflowAnimations.showView(featureNotificationViewHolder.chatNewFeatureNotif, height, 6);

                        return false;
                    }
                });

Answer 1

.notifyDataSetChanged() will notify all of your items inside the RecyclerView, if you don't want everything to reset consider using .notifyItemChanged(int position) method on your adapter instance. You'll need to know exactly the index/position of the item to be notified.

Answer 2

Instead of using notifyDataSetChanged , you should use notifyItemChanged to only change the item that needs to be changed, and not the whole adapter or data set.

This won't lead to the unnecessary animation because you're only changing a specific item. This is also much faster and takes up less processing and rendering power.

You can read more about it here .