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Thursday, March 10, 2016

Comparison between android RecyclerView and ListView

Android is an evolving platform. Recently 5.0 (Lollipop) version of Android was released, along with the official RecyclerView support v7 library. As per the official documentation RecyclerView is a major enhancement over ListView. It contains many new features like ViewHolder, ItemDecorator, LayoutManager, and SmoothScroller. But one thing that certainly gives it an edge over the ListView is; the ability to have animations while adding or removing an item. Here in Android RecyclerView vs ListView sum up I would compare the various features of RecyclerView and ListView and form an opinion why it should be used in new implementations.

Differences Between RecyclerView and ListView

1. View Holders

In ListView, defining view holders was a suggested approach for keeping references for views. But it was not a compulsion. Although by not doing so, ListView used show stale data. Another major drawback of not using view holders could lead to a heavy operation of finding views by ids every time. Which resulted in laggy ListViews.

This problem is solved in RecylerView by the use of RecyclerView.ViewHolder class. This is one of the major differences in RecyclerView and ListView. When implementing a RecyclerView this class is used to define a ViewHolder object which is used by the adapter to bind ViewHolder with a position. Another point to be noted here, is that while implementing the adapter for RecyclerView, providing a ViewHolder is compulsory. This makes the implementation a little complex, but solves the issues faced in ListView.

2. Layout Manager

When speaking of ListViews, only one type of ListView is available i.e. the vertical ListView. You cannot implement a ListView with horizontal scroll. I know there are ways to implement a horizontal scroll, but believe me it was not designed to work that way.

But now when we look at Android RecyclerView vs ListView, we have support for horizontal collections as well. In-fact it supports multiple types of lists. To support multiple types of lists it uses RecyclerView.LayoutManager class. This is something new that ListView does not have. RecyclerView supports three types of predefined Layout Managers:

  • LinearLayoutManager – This is the most commonly used layout manager in case of RecyclerView. Through this, we can create both horizontal and vertical scroll lists.
  • GridLayoutManager– This layout manager can be used to display grids, like any picture gallery.

3. Item Animator

Animations in a list is a whole new dimension, which has endless possibilities. In a ListView, as such there are no special provisions through which one can animate, addition or deletion of items. Instead later on as android evolved ViewPropertyAnimator was suggested by Google’s Chet Haase in this video tutorial for animations in ListView.

On the other hand comparing Android RecyclerView vs ListView, it has RecyclerView.ItemAnimator class for handling animations. Through this class custom animations can be defined for item addition, deletion and move events. Also it provides aDefaultItemAnimator, in case you don’t need any customizations.

4. Adapter

ListView adapters were simple to implement. They had a main method getView where all the magic used to happen. Where the views were bound to a position. Also they used to have an interesting method registerDataSetObserver where one can set an observer right in the adapter. This feature is also present in RecyclerView, but RecyclerView.AdapterDataObserver class is used for it. But the point in favor of ListView is that it supports three default implementations of adapters:

Whereas RecyclerView adapter, has all the functionality that ListView adapters had except the built in support for DB cursors and ArrayLists. In RecyclerView.Adapter as of now we have to make a custom implementation to supply data to the adapter. Just like a BaseAdapter does for ListViews. 

5. Item Decoration
To display custom dividers in a ListView, one could have easily added these parameters in the ListView XML:


The interesting part about Android RecyclerView is that, as of now it does not show a divider between items by default. Although the guys at Google must have left this out for customization, intentionally. But this greatly increases the effort for a developer. If you wish to add a divider between items, you may need to do a custom implementation by using RecyclerView.ItemDecorationclass.

Or you can apply a hack by using this file from official samples:

6. OnItemTouchListener
Listviews used to have a simple implementation for detection of clicks, i.e. by the use of AdapterView.OnItemClickListenerinterface.

But on the other hand RecyclerView.OnItemTouchListener interface is used to detect touch events in Android RecyclerView. It complicates the implementation a little, but it gives a greater control to the developer for intercepting touch events. The official documentation states, it can be useful for gestural manipulations as it intercepts a touch event before it is delivered to RecyclerView.

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