Using RecyclerView Instead Of ViewPager For Gallery

Phimpme is an Image app that provide camera, editing ,sharing options and a gallery section. The Gallery section allows us to view large number of images that are locally available in the users device. Generally developers used viewpager to swipe the horizontal images although we are also using viewPager but the problem is it is taking more time to load large size images and that disturb the user smooth experience. After so much research I came to new solution. So in this post, I will be explaining how to use recyclerview to view gallery images instead of viewPager.

Let’s get started

Make sure you have Recyclerview support in your dependencies in build.gradle. As recyclerView required an adapter and viewHolder to set data in recyclerView. So I will be explaining about adapter.

ViewHolder for RecyclerView

public static class ViewHolder extends RecyclerView.ViewHolder {
  ImageView imageView;
  LinearLayout linearLayout;

  public ViewHolder(View itemView) {
      super(itemView);
      imageView = new ImageView(context);
      linearLayout = (LinearLayout) itemView.findViewById(R.id.layout);
      WindowManager wm = (WindowManager) getContext().getSystemService(Context.WINDOW_SERVICE);
      Display display = wm.getDefaultDisplay();
      Point size = new Point();
      display.getSize(size);
      int width = size.x;
      int height = size.y;
      LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(
              width, height);
      imageView.setLayoutParams(params);
      imageView.setScaleType(ImageView.ScaleType.FIT_CENTER);
      linearLayout.addView(imageView);
  }
}

Right now the imageView is adjusting according to device screen size so that it will be compatible with all devices.

I am passing the width and height in LayoutParams to parent of imageview i.e in our case linearlayout is parentView.

Adapter for RecyclerView

public ImageAdapter(ArrayList<Media> media) {
  this.media = media;
}

@Override
public ImageAdapter.ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
  View view = LayoutInflater.from(parent.getContext()).inflate(R.layout.unit_image_pager, null, false);

  return new ViewHolder(view);
}

@Override
public void onBindViewHolder(ViewHolder holder, int position) {
  Glide.with(getContext())
          .load(media.get(position).getUri())
          .diskCacheStrategy(DiskCacheStrategy.SOURCE)
          .thumbnail(0.5f)
          .into(holder.imageView);
  holder.imageView.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View v) {
          basicCallBack.callBack(0,null);
      }
  });
}

MediaList is an arrray of media that contains the list of images with URI that will help to load images. I am using Glide to load images you can use any library to load images. Adapter helps to load data in recyclerView.

Now set viewPager where you require to scroll images horizontally

@Nullable @BindView(R.id.photos_pager)
RecyclerView mRecylerPager;
mRecylerPager.setLayoutManager(linearLayoutManager);
mRecylerPager.setHasFixedSize(true);
mRecylerPager.setLongClickable(true);

Our recycler view is ready now the most important part is to set things onPageChangeListner. For example : In Phimpme we are getting path of current position image to show in image description so to update the value we are writing that codde in onPageChangeListner and to update the toolbar.

mViewPager.setOnPageChangeListener(new PagerRecyclerView.OnPageChangeListener() {
  @Override
  public void onPageChanged(int oldPosition, int position) {
      getAlbum().setCurrentPhotoIndex(position);
      toolbar.setTitle((position + 1) + " " + getString(R.string.of) + " " + size_all);
      invalidateOptionsMenu();
      pathForDescription = getAlbum().getMedia().get(position).getPath();
  }
});

To scroll to the given position we require to set the position to recyclerView and it can be done by the following code

mViewPager.scrollToPosition(getCurrentPsotion());

This is how I implemented the recyclerView instead of ViewPager to load gallery images faster as compare to ViewPager.

RecyclerView in Phimpme to load gallery Images

Resources:     

 

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Implementing Tweet Search feature in Loklak Wok Android

Loklak Wok Android is a peer harvester that posts collected tweets to the Loklak Server. Along with that tweets can be searched using the app. This post describes how search API endpoint and TabLayout is used to implement the tweet searching feature.

Adding Dependencies to the project

This feature uses Retrofit2, Reactive extensions(RxJava2, RxAndroid and Retrofit RxJava adapter) and RetroLambda (for Java lambda support in Android).

In app/build.gradle:

apply plugin: 'com.android.application'
apply plugin: 'me.tatarka.retrolambda'

android {
   ...
   packagingOptions {
       exclude 'META-INF/rxjava.properties'
   }
}

dependencies {
   ...
   compile 'com.google.code.gson:gson:2.8.1'

   compile 'com.squareup.retrofit2:retrofit:2.3.0'
   compile 'com.squareup.retrofit2:converter-gson:2.3.0'
   compile 'com.squareup.retrofit2:adapter-rxjava2:2.3.0'

   compile 'io.reactivex.rxjava2:rxjava:2.0.5'
   compile 'io.reactivex.rxjava2:rxandroid:2.0.1'
}

 

In build.gradle project level:

dependencies {
   classpath 'com.android.tools.build:gradle:2.3.3'
   classpath 'me.tatarka:gradle-retrolambda:3.2.0'
}

 

Implementation

The search API endpoint is defined in LoklakApi interface which would provide the tweet search result.

public interface LoklakApi {

   @GET("api/search.json")
   Observable<Search> getSearchedTweets(
           @Query("q") String query,
           @Query("filter") String filter,
           @Query("count") int count);
}

 

The POJOs (Plain Old Java Objects) for the result of search API endpoint are obtained using jsonschema2pojo, Gson uses POJOs to convert JSON to Java objects and vice-versa.

The REST client is created by Retrofit2 and is implemented in RestClient class. The Gson converter and RxJava adapter for retrofit is added in the retrofit builder. create method is called to generate the API methods(retrofit implements LoklakApi Interface).

public class RestClient {

   private RestClient() {
   }

   private static void createRestClient() {
       sRetrofit = new Retrofit.Builder()
               .baseUrl(BASE_URL)
               // gson converter
               .addConverterFactory(GsonConverterFactory.create(gson))
               // retrofit adapter for rxjava
               .addCallAdapterFactory(RxJava2CallAdapterFactory.create())
               .build();
   }

   private static Retrofit getRetrofitInstance() {
       if (sRetrofit == null) {
           createRestClient();
       }
       return sRetrofit;
   }

   public static <T> T createApi(Class<T> apiInterface) {
       // create method to generate API methods
       return getRetrofitInstance().create(apiInterface);
   }

}

 

As search API endpoint provides filter parameter which can be used to filter out tweets containing images and videos. So, the tweets are displayed in three categories i.e. latest, images and videos.

The tweets of different category are displayed using a ViewPager. The fragments in ViewPager are inflated by a class that extends FragmentPagerAdapter. SearchFragmentPagerAdapter extends FragmentPagerAdapter, at least two methods getItem and getCount needs to be overridden. Going by the name of methods, getItem provides ith fragment to the  ViewPager and based on the value returned by getCount number of tabs are inflated in TabLayout, a ViewGroup to display fragments in ViewPager in an elegant way. For better UI, the names (here the category of tweets) are displayed, for which we override getPageTitle method.

public class SearchFragmentPagerAdapter extends FragmentPagerAdapter {

   private List<Fragment>  mFragmentList = new ArrayList<>();
   private List<String> mFragmentNameList = new ArrayList<>();

   public SearchFragmentPagerAdapter(FragmentManager fm) {
       super(fm);
   }

   @Override
   public Fragment getItem(int position) {
       return mFragmentList.get(position);
   }

   @Override
   public int getCount() {
       return mFragmentList.size();
   }

   @Override
   public CharSequence getPageTitle(int position) {
       return mFragmentNameList.get(position);
   }

   public void addFragment(Fragment fragment, String pageTitle) {
       mFragmentList.add(fragment);
       mFragmentNameList.add(pageTitle);
   }
}

 

For easy understanding an analogy with RecyclerView can be made. The TabLayout here functions as a RecyclerView, ViewPager does the work of LayoutManager and FragmentPagerAdapter is analogous to RecyclerView.Adapter.

Now, the fragments which contain the categorical tweets are inflated in the parent fragment. Firstly, the ViewPager of TabLayout is set. Then fragments and their names are added to the FragmentPagerAdapter using the addFragment method implemented in SearchFragmentAdapter class above and finally the created adapter is set as the adapter of ViewPager, which is implemented in setupWithViewPager method.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                        Bundle savedInstanceState) {
   // Inflate the layout for this fragment
   View rootView = inflater.inflate(R.layout.fragment_search, container, false);
   ButterKnife.bind(this, rootView);
   ...
   tabLayout.setupWithViewPager(viewPager);
   setupViewPager(viewPager);

   return rootView;
}

private void setupViewPager(ViewPager viewPager) {
   FragmentManager fragmentManager = getActivity().getSupportFragmentManager();
   SearchFragmentPagerAdapter pagerAdapter = new SearchFragmentPagerAdapter(fragmentManager);
   pagerAdapter.addFragment(SearchCategoryFragment.newInstance("", mQuery), "LATEST");
   pagerAdapter.addFragment(SearchCategoryFragment.newInstance("image", mQuery), "PHOTOS");
   pagerAdapter.addFragment(SearchCategoryFragment.newInstance("video", mQuery), "VIDEOS");
   viewPager.setAdapter(pagerAdapter);
}

 

SearchCategoryFragment are child fragments displayed as tabs in TabLayout. These child fragments are created using newInstance method which takes two parameters, category of tweets and the tweet search query respectively, the reason a constructor with these parameters are not used is that during a orientation change only the default constructor i.e. with no parameters is restored by Android system. So, these parameters are stored in a data structure called Bundle, once the fragment object is created using the default parameter the arguments present in the bundle are passed to fragment using setArguments method. These parameter are retrieved in onCreate lifecycle callback method of fragment which are used to fetch search results.

public static SearchCategoryFragment newInstance(String category, String query) {
   Bundle args = new Bundle();
   // query and category stored in bundle
   args.putString(Constants.TWEET_SEARCH_SUGGESTION_QUERY_KEY, query);
   args.putString(TWEET_SEARCH_CATEGORY_KEY, category);
   // fragment with default constructor created
   SearchCategoryFragment fragment = new SearchCategoryFragment();
   // arguments in bundle are passed to fragment
   fragment.setArguments(args);
   return fragment;
}

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
   super.onCreate(savedInstanceState);
   Bundle bundle = getArguments();
   if (bundle != null) {
       // arguments retrieved
       mTweetSearchCategory = bundle.getString(TWEET_SEARCH_CATEGORY_KEY);
       mSearchQuery = bundle.getString(Constants.TWEET_SEARCH_SUGGESTION_QUERY_KEY);
   }
}

 

As we have search query and category we can now obtain the search result and pass the obtained result – a List of type Status – to the adapter of RecyclerView which shows the tweets beautifully inside a CardView. The adapter and LayoutManager of RecyclerView are instantiated and set in onCreateView lifecycle callback method. Finally, network request is sent by calling fetchSearchedTweets method to obtain the search results.

@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                        Bundle savedInstanceState) {
   // Inflate the layout for this fragment
   View view = inflater.inflate(R.layout.fragment_search_category, container, false);
   ButterKnife.bind(this, view);

   mSearchCategoryAdapter = new SearchCategoryAdapter(getActivity(), new ArrayList<>());
   recyclerView.setLayoutManager(new LinearLayoutManager(getActivity()));
   recyclerView.setAdapter(mSearchCategoryAdapter);

   // request sent to obtain search result.
   fetchSearchedTweets();

   return view;
}

 

The LoklakApi interface is implemented using the created Rest client and then getSearchedTweets method is invoked which takes in search query, category of tweets and maximum number of results in the mentioned order. If the network request is successful then setSearchResultView is invoked else setNetworkErrorView.

private void fetchSearchedTweets() {
   LoklakApi loklakApi = RestClient.createApi(LoklakApi.class);
   loklakApi.getSearchedTweets(mSearchQuery, mTweetSearchCategory, 30)
           .subscribeOn(Schedulers.io()) // network request sent in a background thread
           .observeOn(AndroidSchedulers.mainThread())
           .subscribe(this::setSearchResultView, this::setNetworkErrorView);
}

 

setSearchResultView displays the obtained result if any in RecyclerView else shows a message that there is no result for the search query.

private void setSearchResultView(Search search) {
   List<Status> statusList = search.getStatuses();
   networkErrorTextView.setVisibility(View.GONE);
   if (statusList.size() == 0) { // request successful but no results
       recyclerView.setVisibility(View.GONE);

       Resources res = getResources();
       String noSearchResultMessage = res.getString(R.string.no_search_match, mSearchQuery); // no result matched message
       // no result message displayed
       noSearchResultFoundTextView.setVisibility(View.VISIBLE);
       noSearchResultFoundTextView.setText(noSearchResultMessage);
   } else { // there are some results, so display them in RecyclerView
       recyclerView.setVisibility(View.VISIBLE);
       mSearchCategoryAdapter.setStatuses(statusList);
   }
}

 

In case of a failed network request, a TextView is displayed asking the user to check the network connections and click on it to retry.

private void setNetworkErrorView(Throwable throwable) {
   Log.e(LOG_TAG, throwable.toString());
   recyclerView.setVisibility(View.GONE);
   networkErrorTextView.setVisibility(View.VISIBLE);
}

 

When the TextView, networkErrorTextView, is clicked a network request is sent again and the visibility of networkErrorTextView is changed to GONE, as implemented in setOnClickNetworkErrorTextViewListner

@OnClick(R.id.network_error)
public void setOnClickNetworkErrorTextViewListener() {
   networkErrorTextView.setVisibility(View.GONE);
   fetchSearchedTweets();
}

 

References:

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