In my previous article we discuss about 3D effect and SlidingRoot drawer animation and many more animations libraries but today i come with ExpandingCollection Android Library which is a card peek/pop controller. For more you can see demo above :

Requirements

• Android 4.0 IceCreamSandwich (API lvl 14) or greater
• Your favorite IDE

Installation

​ maven repo:

Gradle:

'com.ramotion.expandingcollection:expanding-collection:0.9.0'

SBT:

libraryDependencies += "com.ramotion.expandingcollection" % "expanding-collection" % "0.9.0"

Maven:

<dependency>
  <groupId>com.ramotion.expandingcollection</groupId>
  <artifactId>expanding-collection</artifactId>
  <version>0.9.0</version>
</dependency>

How to Add ExpandingCollection Android Library

Add a background switcher element ECBackgroundSwitcherView and a main pager element ECPagerView to your layout. ECPagerView should always have match_parent width and wrap_content height. You can adjust the vertical position yourself using alignment/gravity or top margin. ECBackgroundSwitcherView is the dynamic background switcher, so you probably want it to be as big as its parent.

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    
    <com.ramotion.expandingcollection.ECBackgroundSwitcherView
        android:id="@+id/ec_bg_switcher_element"
        android:layout_width="match_parent"
        android:layout_height="match_parent" />
        
    <com.ramotion.expandingcollection.ECPagerView
        android:id="@+id/ec_pager_element"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_centerInParent="true"/>
        
</RelativeLayout>

Tune ECPagerView: setup size of card in collapsed state and height of header in expanded state.

<com.ramotion.expandingcollection.ECPagerView xmlns:ec="http://schemas.android.com/apk/res-auto"
    android:id="@+id/ec_pager_element"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_centerInParent="true"
    ec:cardHeaderHeightExpanded="150dp"
    ec:cardHeight="200dp"
    ec:cardWidth="250dp" />

Expanded card contains two parts: a header part with a background (initially visible when card is collapsed) and a ListView element as content (visible only when card is expanded), so you need an xml layout for the list items.

<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="wrap_content">
    
    <TextView xmlns:android="http://schemas.android.com/apk/res/android"
        android:id="@+id/list_item_text"
        android:layout_width="match_parent"
        android:layout_height="100dp"
        android:layout_gravity="center_vertical|center_horizontal"
        android:background="@color/colorPrimary"
        android:textAlignment="center" />
        
</FrameLayout>

Also, you need to implement a custom list adapter for the list items by extending the parametrized com.ramotion.expandingcollection.ECCardContentListItemAdapter.javaclass, where T is type of datasource object for list items inside the card. In the example below, T is just a string object. It’s a pretty straightforward implementation with a common view holder pattern.

public class CardListItemAdapter extends ECCardContentListItemAdapter<String> {

    public CardListItemAdapter(@NonNull Context context, @NonNull List<String> objects) {
        super(context, R.layout.list_item, objects);
    }

    @NonNull
    @Override
    public View getView(int position, @Nullable View convertView, @NonNull ViewGroup parent) {
        ViewHolder viewHolder;
        View rowView = convertView;

        if (rowView == null) {
            LayoutInflater inflater = LayoutInflater.from(getContext());
            rowView = inflater.inflate(R.layout.list_item, null);
            viewHolder = new ViewHolder();
            viewHolder.itemText = (TextView) rowView.findViewById(R.id.list_item_text);
            rowView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) rowView.getTag();
        }

        String item = getItem(position);
        if (item != null) {
            viewHolder.itemText.setText(item);
        }
        return rowView;
    }

    static class ViewHolder {
        TextView itemText;
    }

}

Your data class must implement the com.ramotion.expandingcollection.ECCardData.javainterface where T is type of datasource object for list items inside the card.

public class CardDataImpl implements ECCardData<String> {

    private String cardTitle;
    private Integer mainBackgroundResource;
    private Integer headBackgroundResource;
    private List<String> listItems;

    @Override
    public Integer getMainBackgroundResource() {
        return mainBackgroundResource;
    }

    @Override
    public Integer getHeadBackgroundResource() {
        return headBackgroundResource;
    }

    @Override
    public List<String> getListItems() {
        return listItems;
    }
}

Almost done! The last thing we need to do is provide our dataset to a pager element through a pager adapter. It’s just an implementation of the abstract class com.ramotion.expandingcollection.ECPagerViewAdapter.java with one abstract method, so it can be easily implemented inside your activity.

public class MainActivity extends Activity {

   private ECPagerView ecPagerView;

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);

       // Get pager from layout
       ecPagerView = (ECPagerView) findViewById(R.id.ec_pager_element);

       // Generate example dataset
       List<ECCardData> dataset = CardDataImpl.generateExampleData();

       // Implement and pager adapter and set it to pager view
       ecPagerView.setPagerViewAdapter(new ECPagerViewAdapter(getApplicationContext(), dataset) {
           @Override
           public void instantiateCard(LayoutInflater inflaterService, ViewGroup head, ListView list, ECCardData data) {
               // Data object for current card
               CardDataImpl cardData = (CardDataImpl) data;

               // Set adapter and items to current card content list
               list.setAdapter(new CardListItemAdapter(getApplicationContext(), cardData.getListItems()));
               // Also some visual tuning can be done here
               list.setBackgroundColor(Color.WHITE);

               // Here we can create elements for head view or inflate layout from xml using inflater service
               TextView cardTitle = new TextView(getApplicationContext());
               cardTitle.setText(cardData.getCardTitle());
               cardTitle.setTextSize(COMPLEX_UNIT_DIP, 20);
               FrameLayout.LayoutParams layoutParams = new FrameLayout.LayoutParams(FrameLayout.LayoutParams.WRAP_CONTENT, FrameLayout.LayoutParams.WRAP_CONTENT);
               layoutParams.gravity = Gravity.CENTER;
               head.addView(cardTitle, layoutParams);

               // Card toggling by click on head element view
               head.setOnClickListener(new View.OnClickListener() {
                   @Override
                   public void onClick(final View v) {
                       ecPagerView.toggle();
                   }
               });
           }
       });

       // Add background switcher to pager view
       ecPagerView.setBackgroundSwitcherView((ECBackgroundSwitcherView) findViewById(R.id.ec_bg_switcher_element));

   }

   // Card collapse on back pressed
   @Override
   public void onBackPressed() {
       if (!ecPagerView.collapse())
           super.onBackPressed();
   }

}

You can find this and other, more complex, examples in this repository .

Hope you like this tutorial then please comment us with your thoughts.