Recycled Pager Adapter inspired by RecyclerView

FooAdapter.java

package com.example;

import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;

import com.example.Foo;
import com.example.RecycledPagerAdapter;

public class FooAdapter extends RecycledPagerAdapter<FooViewHolder> {

    private List<Foo> data;
    private LayoutInflater layoutInflater;

    @Override
    public FooViewHolder onCreateViewHolder(ViewGroup parent) {
        if (layoutInflater == null) {
            layoutInflater = LayoutInflater.from(parent.getContext());
        }

        // Inflate view
        View v = layoutInflater.inflate(R.layout.item_player_card, parent, false);
        // Return view holder
        return new FooViewHolder(v);
    }

    @Override
    public void onBindViewHolder(FooViewHolder viewHolder, int position) {
        // Show foo inside viewHolder
        viewHolder.show(data.get(position));
    }

    @Override
    public int getCount() {
        return data == null ? 0 : data.size();
    }

    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        // TODO: optional callback when current object has changed
    }

    public TrackSet getData() {
        return data;
    }

    public void setData(TrackSet data) {
        if (this.data != data) {
            this.data = data;
            notifyDataSetChanged();
        }
    }

    public static class FooViewHolder extends RecycledPagerAdapter.ViewHolder {
        public FooViewHolder(View v) {
            super(v);
            // TODO: use findViewById or Butterknife
        }

        public void show(Foo foo) {
            // TODO: update views with foo
        }
    }
}

RecycledPagerAdapter.java

package com.example;

import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;

import com.example.RecycledPagerAdapter.ViewHolder;

import java.util.LinkedList;
import java.util.Queue;

/**
 * See https://gist.github.com/tvkkpt/2e667cb707859123b422
 * @param <VH>
 */
public abstract class RecycledPagerAdapter<VH extends ViewHolder> extends PagerAdapter {

    public static abstract class ViewHolder {
        final View itemView;

        public ViewHolder(View itemView) {
            this.itemView = itemView;
        }
    }

    Queue<VH> destroyedItems = new LinkedList<>();

    @Override
    public final Object instantiateItem(ViewGroup container, int position) {
        VH viewHolder = destroyedItems.poll();

        if (viewHolder != null) {
            // Re-add existing view before rendering so that we can make change inside getView()
            container.addView(viewHolder.itemView);
            onBindViewHolder(viewHolder, position);
        } else {
            viewHolder = onCreateViewHolder(container);
            onBindViewHolder(viewHolder, position);
            container.addView(viewHolder.itemView);
        }

        return viewHolder;
    }

    @Override
    public final void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView(((VH) object).itemView);
        destroyedItems.add((VH) object);
    }

    @Override
    public final boolean isViewFromObject(View view, Object object) {
        return ((VH) object).itemView == view;
    }

    /**
     * Create a new view holder
     * @param parent
     * @return view holder
     */
    public abstract VH onCreateViewHolder(ViewGroup parent);

    /**
     * Bind data at position into viewHolder
     * @param viewHolder
     * @param position
     */
    public abstract void onBindViewHolder(VH viewHolder, int position);
}

A small problem with FooAdapter is rotations - the code that saves the layout inflater breaks after a rotation (using old context)
(i.e. the items are inflated with the wrong context - so if you use an item's context in onBindViewHolder it can cause problems - like if you use the context of an imageView with Glide to load an image)

Here's a fix:

if (layoutInflater == null || layoutInflater.getContext() != parent.getContext())

The Best Solution. Because of this solution view pager animation is working very fast and smooth.
Thanks Morgotth 👍

Hi Morgotth,

Thank you for your solution:)

I wonder if there is a way to set the items inside the this view pager onClickListener?
I was searching but cannot find anything that would work for me

Hi DariaKalashnik,

I think it's possible but I would better advise using ViewPager 2,
based on RecyclerView and so better fondations 👍

BTW thx to other comments, happy this gist could help you!