Multiple Views - Recyclerview-CardView

Libraries used

• RecyclerView
• CardView
• GooglePlay Services
• Volley
• Jackson

Project Features Description

• Google Play Services​- To find out user location
• Jacskon​- A library to deserialize JSON data using Object Mapper
• Volley​- To start the request to get the JSON data using custom
  • Volley is faster than using AysncTask
  • It takes care of network handling internally
  • Caches data
  • Allows us to cancel requests attached to a Tag
  • It allows us to create a Custom Request class to execute our request
• I have created a custom request class for using in Volley called ​JacksonRequest
  which extends JSONRequest
• JacksonRequest​allows me to get the JSON response I need using volley and
  Jackson’s Object mapper.
• Using RecyclerView and CardView for smooth scrolling and view re-usability
• A ViewType and a ViewHolder for each card type so that different card types can be
  added in the future.
  • Used a LinkedHashSet to eliminate overlapping content

Additional Functionality
1. Cards can be re-ordered by a long press and drag
2. Cards can be swiped right to delete a card
3. Infinite scrolling is implemented. To show infinite scrolling scrolling i have created a few cards of the ‘Place’ type

 

Q: How would your implementation handle adding 20 more types (e.g. places, movies, events, videos, travel, etc)?

• Add a new ViewType
• Create a new ViewHolder and the corresponding layout
• Hook it all up in the adapter

Q: How does adding 20 more types affect the performance of the app?

• Recycling views improves performance by avoiding the creation of unnecessary views or performing expensive findViewById() lookups.
• For each type of card created the method onCreateViewHolder() is called.
• Each call to onCreateViewHolder() leads to creation of a new instance of ViewHolder
• If there are 20 types and 1 item of each type in the list, onCreateViewHolder() will be called 20 times to create a view for every item.
• If there is 1 type and 20 items of each type, depending on the screen size, lets 7 items fit on the screen, then o​nCreateViewHolder() will be called approximately 8 ­to 9 times.
• Also, onCreateViewHolder() is not called when we view already created
  items, eg. while scrolling up/back in a list
• Having too many types defeats the purpose of ViewHolder pattern. It does not allow us to reuse the views as we don’t have access to s​crap views which are cached

Q: What if these cards are visible in many different locations in the app?

• To use these cards across multiple lists we can use RecycledViewPool
  RecycledViewPool lets us share Views between multiple RecyclerViews.
• If you want to recycle views across RecyclerViews, we create an instance of RecycledViewPool and use setRecycledViewPool(RecycledViewPool)
• RecyclerView automatically creates a pool for itself if you don't provide one.
• This has a method setMaxRecycledViews