RedditDSList

RedditDSList is an application that show how useful the library DSList is for created a recyclerview list in Android.

DSList is:

• Type-safe builder: DSList is base on domain-specific language (DSL), suitable for building complex hierarchical data structures in a semi-declarative way.
• Reactive: DSList use StateFlow to handle the state of the list. This helps you load and display small chunks of data at a time.

Quick Start

Simple example

listDSL<String, RedditPost> {
   recyclerView = this@MainActivity.recyclerView
    
   load {
       when(it) {
           ListState.REFRESH -> print("")
           ListState.PREPEND -> mainViewModel.getPosts(after = null, before = before)
           ListState.APPEND -> mainViewModel.getPosts(after = after, before = null)
       }
   }

   observe(redditPostLiveData) { posts ->
       posts?.let {
           for (value in listOfRedditPost) {
               row {
                   id = key
                   content = value
                   viewType = R.layout.item_reddit_post
                   viewBind { content, itemView ->
                       val title: TextView? =
                           itemView.findViewById(R.id.textView_title)
                       val author: TextView? =
                           itemView.findViewById(R.id.textView_author)
                       title?.text = content.title
                       author?.text = content.author
                   }
               }
           }           
       }
   }
}

Advance example

 recyclerView.layoutManager = LinearLayoutManager(context)
 
 listDSL<String, RedditPost> {
   recyclerView = this@RedditPostFragment.recyclerView
 
   load {
     when(it) {
       ListState.REFRESH -> print("")
       ListState.PREPEND -> redditPostViewModel.getPosts(after = null, before = before)
       ListState.APPEND -> redditPostViewModel.getPosts(after = after, before = null)
     }
   }
 
   observe(redditPostViewModel.redditPost) { posts ->
      posts?.let {
        for (value in it) {
          row {
            id = value.key
            content = value
            viewType = R.layout.item_reddit_post
            viewBind { redditPost, itemView ->
              val title: TextView? =
                  itemView.findViewById(R.id.textView_title)
 
              val image: ImageView? =
                  itemView.findViewById(R.id.imageView)
 
              val playerView: PlayerView? =
                  itemView.findViewById(R.id.playerView)
 
              val cardView: MaterialCardView? =
                  itemView.findViewById(R.id.cardView_post)
 
              if(redditPost.media !== null) {
                val player = initializePlayer()
                playerView?.player = player
                val uri = Uri.parse(redditPost.media.hls_url)
                val mediaSource = buildMediaSource(uri)
                with(player) {
                  volume = 0f
                  playWhenReady = this@RedditPostFragment.playWhenReady
                  seekTo(currentWindow, playbackPosition)
                  repeatMode = Player.REPEAT_MODE_ONE
                  mediaSource?.let { it1 -> prepare(it1, false, false) }
                }

                playerView?.visibility = View.VISIBLE
                image?.visibility = View.GONE
              }else {
                image?.load(redditPost.url)
                playerView?.visibility = View.GONE
                image?.visibility = View.VISIBLE
              }
 
              title?.text = redditPost.title
 
              cardView?.setOnClickListener {
                val bundle = bundleOf("redditPost" to redditPost)
                findNavController().navigate(R.id.action_redditPostFragment_to_redditPostDetailsFragment, bundle)
              }
            }
          }
        }
      }
   }
 }

Documentation of DSList

To build a simple or paged list you can use different functions or properties.

properties

• recyclerView: Instance of RecyclerView class.
• rows: List of Row type.
• after: Last id of the row list.
• before: First id of the row list.

base

First we need to provide the type arguments <Key,Model>.

• Key: Id that is associated to each row. It can be of any type (String, Int, etc)
• Model: Type of data that we want to show in the list, for example an String or data class

data class RedditPost (
   val key: String,
   val title: String,
   val author: String,
)

listDSL<String, RedditPost> {}

Also we need the reference to the RecyclerView visual component.

listDSL<String, RedditPost> {
   recyclerView = this@MainActivity.recyclerView
}

And finally we can use the different functions to build our list

Important: Don't forget to add the layout manager.

recyclerView.layoutManager = LinearLayoutManager(this) // or GridLayoutManager(this,2)

row{}

The row function allows you to add the content of the list and associate it with the visual components that have been defined. You have four properties id, content, viewType and viewBind.

• id: Row identifier (optional)
• content: Row content (optional)
• viewType: Id of the view already designed for the items (required)
• viewBind: Function that associates content with visual components (required)

listDSL<String, RedditPost> {
   recyclerView = this@MainActivity.recyclerView
  
   for (value in listOfRedditPost) {
       row {
           id = key
           content = value
           viewType = R.layout.item_reddit_post
           viewBind { content, itemView ->
               val title: TextView? =
                   itemView.findViewById(R.id.textView_title)
               val author: TextView? =
                   itemView.findViewById(R.id.textView_author)
               title?.text = content.title
               author?.text = content.author
           }
       }
   }
}

observe{}

The observe function allows you to update the items of the list, using for this the LiveData class that allows us to create an observable data holder.

val redditPostLiveData: MutableLiveData<List<RedditPost>> by lazy {
   MutableLiveData<List<RedditPost>>()
}

listDSL<String, RedditPost> {
   recyclerView = this@MainActivity.recyclerView
    
   observe(redditPostLiveData) { posts ->
       posts?.let {
           for (value in listOfRedditPost) {
               row {
                   id = key
                   content = value
                   viewType = R.layout.item_reddit_post
                   viewBind { content, itemView ->
                       val title: TextView? =
                           itemView.findViewById(R.id.textView_title)
                       val author: TextView? =
                           itemView.findViewById(R.id.textView_author)
                       title?.text = content.title
                       author?.text = content.author
                   }
               }
           }           
       }
   }
}

load{}

The load is a reactive function that is call every time we can not scroll further.

• REFRESH: Called when data is update.
• PREPEND: Called when reaches the top of the list.
• APPEND: Called when reaches the bottom of the list.

listDSL<String, RedditPost> {
   recyclerView = this@MainActivity.recyclerView
     
   load {
       when(it) {
           ListState.PREPEND -> mainViewModel.getPosts(after = null, before = before)
           ListState.APPEND -> mainViewModel.getPosts(after = after, before = null)
       }
   }

   observe(redditPostLiveData) { posts ->
       posts?.let {
           for (value in listOfRedditPost) {
               row {
                   id = key
                   content = value
                   viewType = R.layout.item_reddit_post
                   viewBind { content, itemView ->
                       val title: TextView? =
                           itemView.findViewById(R.id.textView_title)
                       val author: TextView? =
                           itemView.findViewById(R.id.textView_author)
                       title?.text = content.title
                       author?.text = content.author
                   }
               }
           }           
       }
   }
}

Creator

Pedro Sánchez Ramírez

License

Copyright (c) 2020, DSList Contributors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

   https://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.