我需要在RecyclerView中有一个ViewPager(类似于水平图库),它垂直显示一个列表. RecyclerView的每一行都有一个ViewPager,允许在某些图像之间滑动. ViewPager还将支持将传播到父RecyclerView的点击事件.
目前,我有以下实现：
列表适配器：
@Override
public void onBindViewHolder(MyHolder holder,int position) {
super.onBindViewHolder(holder,position);
Item listItem = get(position);
...
GalleryAdapter adapter =
new GalleryAdapter(getActivity().getSupportFragmentManager(),item.mediaGallery);
holder.imageGallery.setAdapter(adapter);
...
}
图库适配器：
public class GalleryAdapter extends FragmentStatePagerAdapter {
private final List<Item.Gallery> mItems;
@Bind(R.id.gallery_item)
ImageView galleryView;
public SearchResultsGalleryPagerAdapter(FragmentManager fm,@NonNull ArrayList<Item.Gallery> mediaGallery) {
super(fm);
mItems = mediaGallery;
}
@Override
public Fragment getItem(int position) {
GalleryFragment fragment = GalleryFragment.newInstance(mItems.get(position));
...
return fragment;
}
@Override
public int getCount() {
return null == mItems ? 0 : mItems.size();
}
@Override
public int getItemPosition(Object object) {
//return super.getItemPosition(object);
return PagerAdapter.POSITION_NONE;
}
}
图库片段：
public class GalleryFragment extends Fragment {
private static final String GALLERY_ITEM_BUNDLE_KEY = "gallery_item_bundle_key";
@Bind(R.id.gallery_item)
ImageView mGalleryView;
private Item.Gallery mGalleryItem;
// Empty constructor,required as per Fragment docs
public GalleryFragment() {}
public static SearchResultsGalleryFragment newInstance(Item.Gallery galleryItem) {
GalleryFragment fragment = new GalleryFragment();
// Add the item in the bundle which will be set to the fragment
Bundle bundle = new Bundle();
bundle.putSerializable(GALLERY_ITEM_BUNDLE_KEY,galleryItem);
fragment.setArguments(bundle);
return fragment;
}
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mGalleryItem = (Item.Gallery) getArguments().getSerializable(GALLERY_ITEM_BUNDLE_KEY);
}
@Nullable
@Override
public View onCreateView(LayoutInflater inflater,@Nullable ViewGroup container,@Nullable Bundle savedInstanceState) {
View view = inflater.inflate(R.layout.fragment_gallery_item,container,false);
ButterKnife.bind(this,view);
displayGalleryItem();
return view;
}
private void displayGalleryItem() {
if (null != mGalleryItem) {
Glide.with(getContext()) // Bind it with the context of the actual view used
.load(mGalleryItem.getImageUrl()) // Load the image
.centerCrop() // scale type
.placeholder(R.drawable.default_product_400_land) // temporary holder displayed while the image loads
.crossFade()
.into(mGalleryView);
}
}
}
我遇到的问题是ViewPager的片段没有正确创建和显示.有时它们出现在手动滚动之后(但并非总是如此),在大多数情况下它们根本不出现.
有没有人对我实施的错误有所了解？
解决方法
我已经设法通过直接使用PagerAdapter解决了这个问题.
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.
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