ViewPager inside CardView inside RecyclerView Android

Question

I\'m trying to design something very similar to this design from the Material Design website.

So basically, I have a list of CardViews that each of them has mu

Answer 1

From what I understand you have an simular issue to mine. I have managed to resolve the issue by switching to PagerAdapter as it gives you more control over the pages created and displayed.

This is the solution I came up to:

The PagerAdapter class:

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v4.view.PagerAdapter;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import com.bumptech.glide.Glide;
import com.bumptech.glide.load.DecodeFormat;
import com.peoplepost.android.R;
import com.peoplepost.android.common.listener.ItemClickSupport;
import com.peoplepost.android.network.merv.model.Product;
import java.util.ArrayList;
import java.util.List;

/**
 * 

 * Custom pager adapter which will manually create the pages needed for showing an slide pages gallery.
 * 
 * Created by Ionut Negru on 13/06/16.
 */
public class GalleryAdapter extends PagerAdapter {

    private static final String TAG = "GalleryAdapter";

    private final List mItems;
    private final LayoutInflater mLayoutInflater;
    /**
     * The click event listener which will propagate click events to the parent or any other listener set
     */
    private ItemClickSupport.SimpleOnItemClickListener mOnItemClickListener;

    /**
     * Constructor for gallery adapter which will create and screen slide of images.
     *
     * @param context
     *         The context which will be used to inflate the layout for each page.
     * @param mediaGallery
     *         The list of items which need to be displayed as screen slide.
     */
    public GalleryAdapter(@NonNull Context context,
                                            @NonNull ArrayList mediaGallery) {
        super();

        // Inflater which will be used for creating all the necessary pages
        mLayoutInflater = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

        // The items which will be displayed.
        mItems = mediaGallery;
    }

    @Override
    public int getCount() {
        // Just to be safe, check also if we have an valid list of items - never return invalid size.
        return null == mItems ? 0 : mItems.size();
    }

    @Override
    public boolean isViewFromObject(View view, Object object) {
        // The object returned by instantiateItem() is a key/identifier. This method checks whether
        // the View passed to it (representing the page) is associated with that key or not.
        // It is required by a PagerAdapter to function properly.
        return view == object;
    }

    @Override
    public Object instantiateItem(ViewGroup container, final int position) {
        // This method should create the page for the given position passed to it as an argument.
        // In our case, we inflate() our layout resource to create the hierarchy of view objects and then
        // set resource for the ImageView in it.
        // Finally, the inflated view is added to the container (which should be the ViewPager) and return it as well.

        // inflate our layout resource
        View itemView = mLayoutInflater.inflate(R.layout.fragment_gallery_item, container, false);

        // Display the resource on the view
        displayGalleryItem((ImageView) itemView.findViewById(R.id.gallery_item), mItems.get(position));

        // Add our inflated view to the container
        container.addView(itemView);

        // Detect the click events and pass them to any listeners
        itemView.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (null != mOnItemClickListener) {
                    mOnItemClickListener.onItemClicked(position);
                }
            }
        });

        // Return our view
        return itemView;
    }

    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        // Removes the page from the container for the given position. We simply removed object using removeView()
        // but could’ve also used removeViewAt() by passing it the position.
        try {
            // Remove the view from the container
            container.removeView((View) object);

            // Try to clear resources used for displaying this view
            Glide.clear(((View) object).findViewById(R.id.gallery_item));
            // Remove any resources used by this view
            unbindDrawables((View) object);
            // Invalidate the object
            object = null;
        } catch (Exception e) {
            Log.w(TAG, "destroyItem: failed to destroy item and clear it's used resources", e);
        }
    }

    /**
     * Recursively unbind any resources from the provided view. This method will clear the resources of all the
     * children of the view before invalidating the provided view itself.
     *
     * @param view
     *         The view for which to unbind resource.
     */
    protected void unbindDrawables(View view) {
        if (view.getBackground() != null) {
            view.getBackground().setCallback(null);
        }
        if (view instanceof ViewGroup) {
            for (int i = 0; i < ((ViewGroup) view).getChildCount(); i++) {
                unbindDrawables(((ViewGroup) view).getChildAt(i));
            }
            ((ViewGroup) view).removeAllViews();
        }
    }

    /**
     * Set an listener which will notify of any click events that are detected on the pages of the view pager.
     *
     * @param onItemClickListener
     *         The listener. If {@code null} it will disable any events from being sent.
     */
    public void setOnItemClickListener(ItemClickSupport.SimpleOnItemClickListener onItemClickListener) {
        mOnItemClickListener = onItemClickListener;
    }

    /**
     * Display the gallery image into the image view provided.
     *
     * @param galleryView
     *         The view which will display the image.
     * @param galleryItem
     *         The item from which to get the image.
     */
    private void displayGalleryItem(ImageView galleryView, Item galleryItem) {
        if (null != galleryItem) {
            Glide.with(galleryView.getContext()) // Bind it with the context of the actual view used
                 .load(galleryItem.getImageUrl()) // Load the image
                 .asBitmap() // All our images are static, we want to display them as bitmaps
                 .format(DecodeFormat.PREFER_RGB_565) // the decode format - this will not use alpha at all
                 .centerCrop() // scale type
                 .placeholder(R.drawable.default_product_400_land) // temporary holder displayed while the image loads
                 .animate(R.anim.fade_in) // need to manually set the animation as bitmap cannot use cross fade
                 .thumbnail(0.2f) // make use of the thumbnail which can display a down-sized version of the image
                 .into(galleryView); // Voilla - the target view
        }
    }
}

And the updated onBindViewHolder() of the parent RecyclerView:

@Override
public void onBindViewHolder(MyHolder holder, int position) {
    super.onBindViewHolder(holder, position);

    Item listItem = get(position);

    ...

    GalleryAdapter adapter =
                    new GalleryAdapter(getActivity(), product.mediaGallery);
    // Set the custom click listener on the adapter directly
    adapter.setOnItemClickListener(new ItemClickSupport.SimpleOnItemClickListener() {
        @Override
        public void onItemClicked(int position) {
            // inner view pager page was clicked
        }
    });
    // Set the adapter on the view pager
    holder.imageGallery.setAdapter(adapter);

    ...
}

I noticed a little increase in memory usage, but the UI is very fluid. I guess some further optimizations can be made on how many pages are kept and how they are destroyed and restored.

Your requirements are a little different, but the logic behind it should be the same. I hope this solves your issue.