Adding separators to list of repositories

app/build.gradle

@@ -40,8 +40,8 @@ android {
         jvmTarget = "1.8"
     }
 
-    buildFeatures {
-        viewBinding = true
+    viewBinding {
+        enabled = true
     }
 }
 

app/src/main/java/com/example/android/codelabs/paging/data/GithubPagingSource.kt

@@ -0,0 +1,52 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * 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
+ *
+ *      http://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.
+ */
+
+package com.example.android.codelabs.paging.data
+
+import androidx.paging.PagingSource
+import com.example.android.codelabs.paging.api.GithubService
+import com.example.android.codelabs.paging.api.IN_QUALIFIER
+import com.example.android.codelabs.paging.model.Repo
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.FlowPreview
+import java.io.IOException
+
+// GitHub page API is 1 based: https://developer.github.com/v3/#pagination
+private const val GITHUB_STARTING_PAGE_INDEX = 1
+
+@ExperimentalCoroutinesApi
+@FlowPreview
+class GithubPagingSource(
+        private val service: GithubService,
+        private val query: String
+) : PagingSource<Int, Repo>() {
+    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, Repo> {
+        val position = params.key ?: GITHUB_STARTING_PAGE_INDEX
+        val apiQuery = query + IN_QUALIFIER
+        val apiResponse = service.searchRepos(apiQuery, position, GithubRepository.NETWORK_PAGE_SIZE)
+        return if (apiResponse.isSuccessful) {
+            val repos = apiResponse.body()?.items ?: emptyList()
+            LoadResult.Page(
+                    data = repos,
+                    prevKey = if (position == GITHUB_STARTING_PAGE_INDEX) null else -1,
+                    // if we don't get any results, we consider that we're at the last page
+                    nextKey = if (repos.isEmpty()) null else position + 1
+            )
+        } else {
+            LoadResult.Error(IOException(apiResponse.message()))
+        }
+    }
+}

app/src/main/java/com/example/android/codelabs/paging/data/GithubRepository.kt

@@ -17,19 +17,14 @@
 package com.example.android.codelabs.paging.data
 
 import android.util.Log
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
+import androidx.paging.PagingDataFlow
 import com.example.android.codelabs.paging.api.GithubService
-import com.example.android.codelabs.paging.api.IN_QUALIFIER
 import com.example.android.codelabs.paging.model.Repo
-import com.example.android.codelabs.paging.model.RepoSearchResult
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
-import kotlinx.coroutines.channels.ConflatedBroadcastChannel
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.asFlow
-import java.io.IOException
-
-// GitHub page API is 1 based: https://developer.github.com/v3/#pagination
-private const val GITHUB_STARTING_PAGE_INDEX = 1
 
 /**
  * Repository class that works with local and remote data sources.
@@ -38,73 +33,20 @@ private const val GITHUB_STARTING_PAGE_INDEX = 1
 @ExperimentalCoroutinesApi
 class GithubRepository(private val service: GithubService) {
 
-    // keep the list of all results received
-    private val inMemoryCache = mutableListOf<Repo>()
-
-    // keep channel of results. The channel allows us to broadcast updates so
-    // the subscriber will have the latest data
-    private val searchResults = ConflatedBroadcastChannel<RepoSearchResult>()
-
-    // keep the last requested page. When the request is successful, increment the page number.
-    private var lastRequestedPage = GITHUB_STARTING_PAGE_INDEX
-
-    // avoid triggering multiple requests in the same time
-    private var isRequestInProgress = false
-
     /**
      * Search repositories whose names match the query, exposed as a stream of data that will emit
      * every time we get more data from the network.
      */
-    suspend fun getSearchResultStream(query: String): Flow<RepoSearchResult> {
+    fun getSearchResultStream(query: String): Flow<PagingData<Repo>> {
         Log.d("GithubRepository", "New query: $query")
-        lastRequestedPage = 1
-        requestAndSaveData(query)
-
-        return searchResults.asFlow()
-    }
-
-    suspend fun requestMore(query: String) {
-        requestAndSaveData(query)
-    }
-
-    private suspend fun requestAndSaveData(query: String) {
-        if (isRequestInProgress) return
-
-        isRequestInProgress = true
-
-        val apiQuery = query + IN_QUALIFIER
-        val response = service.searchRepos(apiQuery, lastRequestedPage, NETWORK_PAGE_SIZE)
-        Log.d("GithubRepository", "response $response")
-        if (response.isSuccessful) {
-            if (response.isSuccessful) {
-                val repos = response.body()?.items ?: emptyList()
-                inMemoryCache.addAll(repos)
-                val reposByName = reposByName(query)
-                searchResults.offer(RepoSearchResult.Success(reposByName))
-            } else {
-                Log.d("GithubRepository", "fail to get data")
-                searchResults.offer(RepoSearchResult.Error(IOException(response.message()
-                        ?: "Unknown error")))
-            }
-        } else {
-            Log.d("GithubRepository", "fail to get data")
-            searchResults.offer(RepoSearchResult.Error(IOException(response.message()
-                    ?: "Unknown error")))
-        }
-        lastRequestedPage++
-        isRequestInProgress = false
-    }
 
-    private fun reposByName(query: String): List<Repo> {
-        // from the in memory cache select only the repos whose name or description matches
-        // the query. Then order the results.
-        return inMemoryCache.filter {
-            it.name.contains(query, true) ||
-                    (it.description != null && it.description.contains(query, true))
-        }.sortedWith(compareByDescending<Repo> { it.stars }.thenBy { it.name })
+        return PagingDataFlow(
+                config = PagingConfig(pageSize = NETWORK_PAGE_SIZE),
+                pagingSourceFactory = { GithubPagingSource(service, query) }
+        )
     }
 
     companion object {
-        private const val NETWORK_PAGE_SIZE = 50
+        const val NETWORK_PAGE_SIZE = 50
     }
 }

app/src/main/java/com/example/android/codelabs/paging/ui/ReposAdapter.kt

@@ -17,32 +17,53 @@
 package com.example.android.codelabs.paging.ui
 
 import android.view.ViewGroup
+import androidx.paging.PagingDataAdapter
 import androidx.recyclerview.widget.DiffUtil
-import androidx.recyclerview.widget.ListAdapter
-import com.example.android.codelabs.paging.model.Repo
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+import com.example.android.codelabs.paging.R
 
 /**
  * Adapter for the list of repositories.
  */
-class ReposAdapter : ListAdapter<Repo, androidx.recyclerview.widget.RecyclerView.ViewHolder>(REPO_COMPARATOR) {
+class ReposAdapter : PagingDataAdapter<UiModel, ViewHolder>(UIMODEL_COMPARATOR) {
 
-    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): androidx.recyclerview.widget.RecyclerView.ViewHolder {
-        return RepoViewHolder.create(parent)
+    override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
+        return if(viewType == R.layout.repo_view_item) {
+            RepoViewHolder.create(parent)
+        } else {
+            SeparatorViewHolder.create(parent)
+        }
+    }
+
+    override fun getItemViewType(position: Int): Int {
+        return when(getItem(position)){
+            is UiModel.RepoItem -> R.layout.repo_view_item
+            is UiModel.SeparatorItem -> R.layout.separator_view_item
+            null -> 0
+        }
     }
 
-    override fun onBindViewHolder(holder: androidx.recyclerview.widget.RecyclerView.ViewHolder, position: Int) {
-        val repoItem = getItem(position)
-        if (repoItem != null) {
-            (holder as RepoViewHolder).bind(repoItem)
+    override fun onBindViewHolder(holder: ViewHolder, position: Int) {
+        val uiModel = getItem(position)
+        uiModel.let {
+            when(uiModel){
+                is UiModel.RepoItem -> (holder as RepoViewHolder).bind(uiModel.repo)
+                is UiModel.SeparatorItem -> (holder as SeparatorViewHolder).bind(uiModel.description)
+            }
         }
     }
 
     companion object {
-        private val REPO_COMPARATOR = object : DiffUtil.ItemCallback<Repo>() {
-            override fun areItemsTheSame(oldItem: Repo, newItem: Repo): Boolean =
-                    oldItem.fullName == newItem.fullName
+        private val UIMODEL_COMPARATOR = object : DiffUtil.ItemCallback<UiModel>() {
+            override fun areItemsTheSame(oldItem: UiModel, newItem: UiModel): Boolean {
+                return if (oldItem is UiModel.RepoItem && newItem is UiModel.RepoItem) {
+                    oldItem.repo.fullName == newItem.repo.fullName
+                } else {
+                    false
+                }
+            }
 
-            override fun areContentsTheSame(oldItem: Repo, newItem: Repo): Boolean =
+            override fun areContentsTheSame(oldItem: UiModel, newItem: UiModel): Boolean =
                     oldItem == newItem
         }
     }

app/src/main/java/com/example/android/codelabs/paging/ui/SearchRepositoriesActivity.kt

@@ -17,22 +17,23 @@
 package com.example.android.codelabs.paging.ui
 
 import android.os.Bundle
+import android.util.Log
 import android.view.KeyEvent
 import android.view.View
 import android.view.inputmethod.EditorInfo
 import android.widget.Toast
 import androidx.appcompat.app.AppCompatActivity
 import androidx.lifecycle.ViewModelProvider
-import androidx.lifecycle.observe
+import androidx.lifecycle.lifecycleScope
+import androidx.paging.LoadState
 import androidx.recyclerview.widget.DividerItemDecoration
-import androidx.recyclerview.widget.LinearLayoutManager
-import androidx.recyclerview.widget.RecyclerView
-import androidx.recyclerview.widget.RecyclerView.OnScrollListener
 import com.example.android.codelabs.paging.Injection
 import com.example.android.codelabs.paging.databinding.ActivitySearchRepositoriesBinding
-import com.example.android.codelabs.paging.model.RepoSearchResult
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.FlowPreview
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.collect
+import kotlinx.coroutines.launch
 
 @FlowPreview
 @ExperimentalCoroutinesApi
@@ -41,6 +42,7 @@ class SearchRepositoriesActivity : AppCompatActivity() {
     private lateinit var binding: ActivitySearchRepositoriesBinding
     private lateinit var viewModel: SearchRepositoriesViewModel
     private val adapter = ReposAdapter()
+    private var searchJob: Job? = null
 
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
@@ -55,11 +57,20 @@ class SearchRepositoriesActivity : AppCompatActivity() {
         // add dividers between RecyclerView's row items
         val decoration = DividerItemDecoration(this, DividerItemDecoration.VERTICAL)
         binding.list.addItemDecoration(decoration)
-        setupScrollListener()
 
-        initAdapter()
+        binding.list.adapter = adapter
+        adapter.addLoadStateListener { loadType, loadState ->
+            Log.d("SearchRepositoriesActivity", "adapter load: type = $loadType state = $loadState")
+            if (loadState is LoadState.Error) {
+                Toast.makeText(
+                        this,
+                        "\uD83D\uDE28 Wooops $loadState.message}",
+                        Toast.LENGTH_LONG
+                ).show()
+            }
+        }
         val query = savedInstanceState?.getString(LAST_SEARCH_QUERY) ?: DEFAULT_QUERY
-        viewModel.searchRepo(query)
+        search(query)
         initSearch(query)
     }
 
@@ -68,25 +79,6 @@ class SearchRepositoriesActivity : AppCompatActivity() {
         outState.putString(LAST_SEARCH_QUERY, binding.searchRepo.text.trim().toString())
     }
 
-    private fun initAdapter() {
-        binding.list.adapter = adapter
-        viewModel.repoResult.observe(this) { result ->
-            when (result) {
-                is RepoSearchResult.Success -> {
-                    showEmptyList(result.data.isEmpty())
-                    adapter.submitList(result.data)
-                }
-                is RepoSearchResult.Error -> {
-                    Toast.makeText(
-                            this,
-                            "\uD83D\uDE28 Wooops $result.message}",
-                            Toast.LENGTH_LONG
-                    ).show()
-                }
-            }
-        }
-    }
-
     private fun initSearch(query: String) {
         binding.searchRepo.setText(query)
 
@@ -112,8 +104,21 @@ class SearchRepositoriesActivity : AppCompatActivity() {
         binding.searchRepo.text.trim().let {
             if (it.isNotEmpty()) {
                 binding.list.scrollToPosition(0)
-                viewModel.searchRepo(it.toString())
-                adapter.submitList(null)
+                search(it.toString())
+                // TODO how to clear the list
+                //  might not need it because of how Paging works
+//                adapter.collectFrom(PagingData.empty())
+            }
+        }
+    }
+
+    private fun search(query: String) {
+        // Make sure we cancel the previous job before creating a new one
+        searchJob?.cancel()
+        searchJob = lifecycleScope.launch {
+            viewModel.searchRepo(query).collect {
+                Log.d("SearchRepositoriesActivity", "query: $query, collecting $it")
+                adapter.presentData(it)
             }
         }
     }
@@ -128,20 +133,6 @@ class SearchRepositoriesActivity : AppCompatActivity() {
         }
     }
 
-    private fun setupScrollListener() {
-        val layoutManager = binding.list.layoutManager as LinearLayoutManager
-        binding.list.addOnScrollListener(object : OnScrollListener() {
-            override fun onScrolled(recyclerView: RecyclerView, dx: Int, dy: Int) {
-                super.onScrolled(recyclerView, dx, dy)
-                val totalItemCount = layoutManager.itemCount
-                val visibleItemCount = layoutManager.childCount
-                val lastVisibleItem = layoutManager.findLastVisibleItemPosition()
-
-                viewModel.listScrolled(visibleItemCount, lastVisibleItem, totalItemCount)
-            }
-        })
-    }
-
     companion object {
         private const val LAST_SEARCH_QUERY: String = "last_search_query"
         private const val DEFAULT_QUERY = "Android"