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android – Partial update of RecyclerView.ViewHolder

Posted by: admin April 23, 2020 Leave a comment

Questions:

I’m trying to change the field with time in my RecyclerView. Each individual ViewHolder contains a CardView and a few more views inside. The only view I want to animate is the one with time. As you can see, there is no animation:

adapter.notifyDataSetChanged();

RecyclerView with no animations

Updating items one by one doesn’t help because then the whole CardView flashes:

int len = adapter.getItemCount();
for(int i=0;i<len;i++) {
    adapter.notifyItemChanged(i);
}

enter image description here

Is there a way to get a list of all ViewHolders to then update (animate) just that one TextView inside each one?

How to&Answers:

You can notify your RecyclerView.Adapter‘s observers to issue a partial update of your RecyclerView.ViewHolders by passing a payload Object.

notifyItemRangeChanged(positionStart, itemCount, payload);

Where payload could be or contain a flag that represents relative or absolute time. To bind the payload to your view holders, override the following onBindViewHolder(viewHolder, position, payloads) method in your adapter, and check the payloads parameter for data.

@Override
public void onBindViewHolder(MyViewHolder viewHolder, int position, List<Object> payloads) {
    if (payloads.isEmpty()) {
        // Perform a full update
        onBindViewHolder(viewHolder, position);
    } else {
        // Perform a partial update
        for (Object payload : payloads) {
            if (payload instanceof TimeFormatPayload) {
                viewHolder.bindTimePayload((TimeFormatPayload) payload);
            }
        }
    }
}

Within your MyViewHolder.bindTimePayload(payload) method, update your time TextViews to the time format specified in the payload.