android – 在RecyclerView里面的ViewPager作为行项目

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;

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

    private static final String TAG = "GalleryAdapter";

    private final List<Item> 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<Item> 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,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
        }
    }
}

并且更新了父RecyclerView的onBindViewHolder()：

@Override
public void onBindViewHolder(MyHolder 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);

    ...
}

我注意到内存使用量略有增加,但UI非常流畅.我想可以进一步优化保存多少页面以及如何销毁和恢复它们.

我希望这能帮助处于类似情况的其他人.