Java RecyclerView仅在滚动时加载图像

以下是我的活动：

public class MainActivity extends AppCompatActivity {

    private RecyclerView mRecyclerView;
    private List<GalleryItem> mGalleryItems;
    GalleryAdapter adapter;
    private boolean loading = true;
    int pastVisiblesItems, visibleItemCount, totalItemCount;
    LinearLayoutManager mLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRecyclerView = (RecyclerView) findViewById(R.id.grid_view);
        mGalleryItems = new ArrayList<>();
        mLayoutManager = new LinearLayoutManager(this);
        mRecyclerView.setLayoutManager(mLayoutManager);
        getItems("http://www.reddit.com/r/aww.json");
        mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                if (dy > 0) {
                    visibleItemCount = mLayoutManager.getChildCount();
                    totalItemCount = mLayoutManager.getItemCount();
                    pastVisiblesItems = mLayoutManager.findFirstVisibleItemPosition();
                    if (loading) {
                        if ((visibleItemCount + pastVisiblesItems) >= totalItemCount) {
                            loading = false;
                            Log.v("...", "Last Item Wow !");
                            getItems("https://www.reddit.com/r/aww.json?after=t3_40x6ke");
                        }
                    }
                }
            }
        });

        adapter = new GalleryAdapter(mGalleryItems, this);
        mRecyclerView.setAdapter(adapter);

    }


    @Override
    public void onDestroy(){
        super.onDestroy();

    }
    public void getItems(String url){
        OkHttpClient client = new OkHttpClient();
        File cacheDirectory = new File(MainActivity.this.getCacheDir(), "http");
        int cacheSize = 10 * 1024 * 1024;
        Cache cache = new Cache(cacheDirectory, cacheSize);
        client.setCache(cache);
        Request request = new Request.Builder()
                .url(url)
                .build();
        Call call = client.newCall(request);
        call.enqueue(new Callback() {
            @Override
            public void onFailure(Request request, IOException e) {

            }

            @Override
            public void onResponse(Response response) throws IOException {
                final String json = response.body().string();
                if (response.isSuccessful()) {
                        try {
                            mGalleryItems.addAll(parseItems(json));
                        } catch (JSONException e) {
                            e.printStackTrace();
                            Log.i("BEHS", e.getMessage());
                        }
                        runOnUiThread(new Runnable() {
                            @Override
                            public void run() {
                                adapter.notifyDataSetChanged();

                            }
                        });
                }
            }
        });

    }

    private List<GalleryItem> parseItems(String json) throws JSONException {
        JSONObject jsonMovie = new JSONObject(json);
        JSONObject firstData = jsonMovie.getJSONObject("data");
        JSONArray children = firstData.getJSONArray("children");

        List<GalleryItem> items = new ArrayList();

        for(int i = 0; i < children.length(); i++ ){
            JSONObject jsonObject = children.getJSONObject(i);
            JSONObject childrenObject = jsonObject.getJSONObject("data");
            GalleryItem item = new GalleryItem();
            item.setTitle(childrenObject.getString("title"));
            item.setUrl(childrenObject.getString("url"));
            item.setThumbnail(childrenObject.getString("thumbnail"));
            //if(!childrenObject.getString("url").endsWith(".jpg")){
         //       continue;
       //     }else{
                items.add(item);
     //       }
        }


        return items;
    }



    private class GalleryHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
        private ImageView mImageView;
        private TextView mTextView;
        private String mUrl;

        public GalleryHolder(View itemView) {
            super(itemView);
            itemView.setOnClickListener(this);
            mImageView = (ImageView) itemView.findViewById(R.id.country_photo);
            mTextView = (TextView) itemView.findViewById(R.id.country_name);
        }


        public void bindImage(GalleryItem item ){
            Picasso.with(MainActivity.this).load(item.getThumbnail()).tag(MainActivity.this).into(new Target() {
                @Override
                public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                    Palette pallete = Palette.from(bitmap).generate();
                    int color = pallete.getMutedColor(MainActivity.this.getResources().getColor(android.R.color.black));
                    mTextView.setBackgroundColor(color);
                    mImageView.setImageBitmap(bitmap);
                }

                @Override
                public void onBitmapFailed(Drawable errorDrawable) {

                }

                @Override
                public void onPrepareLoad(Drawable placeHolderDrawable) {

                }
            });
        }

        public void bindUrl(String url){
            mUrl = url;
        }

        @Override
        public void onClick(View view) {
            Intent i = new Intent(MainActivity.this, ItemActivity.class);
            i.putExtra("url", mUrl);
            Log.i(mUrl, mUrl);
            startActivity(i);

        }
    }

    private class GalleryAdapter extends RecyclerView.Adapter<GalleryHolder>{
        private List<GalleryItem> mImages;
        private Context mContext;

        public GalleryAdapter(List<GalleryItem> images, Context context){
            mContext = context;
            mImages = images;
        }

        @Override
        public GalleryHolder onCreateViewHolder(ViewGroup parent, int viewType) {
            LayoutInflater inflater = LayoutInflater.from(MainActivity.this);
            View view = inflater.inflate(R.layout.list_item, parent, false);
            return new GalleryHolder(view);

        }

        @Override
        public void onBindViewHolder(GalleryHolder holder, int position) {
            holder.mTextView.setText(mImages.get(position).getTitle());
            holder.mImageView.setImageBitmap(null);
            holder.bindImage(mImages.get(position));
            holder.bindUrl(mImages.get(position).getUrl());

        }
        @Override
        public long getItemId(int position) {
            return position;
        }

        @Override
        public int getItemCount() {
            return mImages.size();
        }
    }
}

public类MainActivity扩展了AppCompatActivity{
私人回收视图mRecyclerView；
私有列表管理项目；
厨房适配器；
私有布尔加载=真；
int pastVisiblesItems、visibleItemCount、totalItemCount；
直线布局经理mLayoutManager；
@凌驾
创建时受保护的void（Bundle savedInstanceState）{
super.onCreate（savedInstanceState）；
setContentView（R.layout.activity_main）；
mRecyclerView=（RecyclerView）findViewById（R.id.grid\u视图）；
mGalleryItems=newArrayList（）；
mLayoutManager=新的LinearLayoutManager（此）；
mRecyclerView.setLayoutManager（mllayoutmanager）；
获取项目（“http://www.reddit.com/r/aww.json");
mrecycleView.addOnScrollListener（新的RecycleView.OnScrollListener（）{
@凌驾
已填空的公共空间（RecyclerView RecyclerView、int dx、int dy）{
super.onScrolled（recyclerView、dx、dy）；
如果（dy>0）{
visibleItemCount=mLayoutManager.getChildCount（）；
totalItemCount=mLayoutManager.getItemCount（）；
pastVisiblesItems=mLayoutManager.findFirstVisibleItemPosition（）；
如果（装载）{
如果（（visibleItemCount+pastVisiblesItems）>=totalItemCount）{
加载=假；
Log.v（“…”，“最后一项哇！”）；
获取项目（“https://www.reddit.com/r/aww.json?after=t3_40x6ke");
}
}
}
}
});
适配器=新的GalleryAdapter（mGalleryItems，this）；
mRecyclerView.setAdapter（适配器）；
}
@凌驾
公共空间{
super.ondestory（）；
}
公共void getItems（字符串url）{
OkHttpClient=新的OkHttpClient（）；
File cacheDirectory=新文件（MainActivity.this.getCacheDir（），“http”）；
int cacheSize=10*1024*1024；
Cache Cache=新缓存（cacheDirectory，cacheSize）；
setCache（cache）；
Request Request=newrequest.Builder（）
.url（url）
.build（）；
Call Call=client.newCall（请求）；
call.enqueue（新回调（）{
@凌驾
公共void onFailure（请求，IOE异常）{
}
@凌驾
public void onResponse（Response-Response）引发IOException{
最后一个字符串json=response.body（）.String（）；
if（response.issusccessful（））{
试一试{
mGalleryItems.addAll（parseItems（json））；
}捕获（JSONException e）{
e、 printStackTrace（）；
Log.i（“BEHS”，即getMessage（））；
}
runOnUiThread（新的Runnable（）{
@凌驾
公开募捐{
adapter.notifyDataSetChanged（）；
}
});
}
}
});
}
私有列表parseItems（字符串json）抛出JSONException{
JSONObject jsonMovie=新的JSONObject（json）；
JSONObject firstData=jsonMovie.getJSONObject（“数据”）；
JSONArray children=firstData.getJSONArray（“children”）；
列表项=新建ArrayList（）；
for（int i=0；i private class GalleryHolder extends RecyclerView.ViewHolder implements View.OnClickListener{
        private ImageView mImageView;
        private TextView mTextView;
        ....
        com.squareup.picasso.Target target = new com.squareup.picasso.Target() {
            @Override
            public void onBitmapLoaded(Bitmap bitmap, Picasso.LoadedFrom from) {
                mTextView.setBackgroundColor(Color.RED);
                mImageView.setImageBitmap(bitmap);
            }

            @Override
            public void onBitmapFailed(Drawable errorDrawable) {}

            @Override
            public void onPrepareLoad(Drawable placeHolderDrawable) {}
        };
        ....
        public void bindImage(GalleryItem item ){
            Picasso.with(MainActivity.this).load(item.getThumbnail()).tag(MainActivity.this).into(target);
        }
    }