Add Paging 3.0 for gallery screen (android#629)

* Add Paging dependency Also updates RecyclerView version and update ShareCompat API call * Update UnsplashService param order Move client_id to the last param * Implement Paging 3.0 Also remove default values for UnsplashService#searchPhotos * Remove unused method * Update paging version Co-authored-by: Florina Muntenescu <[email protected]> * Update recyclerview version Co-authored-by: Florina Muntenescu <[email protected]> * Address PR comments - catch Exception instead of IO/HttpException - disable Paging placeholders - remove unneeded local variable in searchPictures Co-authored-by: Florina Muntenescu <[email protected]>
rColeJnr · Jul 15, 2020 · a4e9eac · a4e9eac
1 parent 4ea76fb
commit a4e9eac
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Showing 11 changed files with 93 additions and 92 deletions.
diff --git a/app/build.gradle b/app/build.gradle
@@ -70,6 +70,7 @@ dependencies {
     implementation "androidx.lifecycle:lifecycle-viewmodel-ktx:$rootProject.lifecycleVersion"
     implementation "androidx.navigation:navigation-fragment-ktx:$rootProject.navigationVersion"
     implementation "androidx.navigation:navigation-ui-ktx:$rootProject.navigationVersion"
+    implementation "androidx.paging:paging-runtime:$rootProject.pagingVersion"
     implementation "androidx.recyclerview:recyclerview:$rootProject.recyclerViewVersion"
     implementation "androidx.room:room-runtime:$rootProject.roomVersion"
     implementation "androidx.room:room-ktx:$rootProject.roomVersion"

diff --git a/app/src/main/java/com/google/samples/apps/sunflower/GalleryFragment.kt b/app/src/main/java/com/google/samples/apps/sunflower/GalleryFragment.kt
@@ -22,20 +22,22 @@ import android.view.View
 import android.view.ViewGroup
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.viewModels
-import androidx.lifecycle.observe
+import androidx.lifecycle.lifecycleScope
 import androidx.navigation.findNavController
 import androidx.navigation.fragment.navArgs
-import com.google.android.material.snackbar.Snackbar
 import com.google.samples.apps.sunflower.adapters.GalleryAdapter
-import com.google.samples.apps.sunflower.data.UnsplashSearchResult
 import com.google.samples.apps.sunflower.databinding.FragmentGalleryBinding
 import com.google.samples.apps.sunflower.utilities.InjectorUtils
 import com.google.samples.apps.sunflower.viewmodels.GalleryViewModel
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.flow.collectLatest
+import kotlinx.coroutines.launch
 
 class GalleryFragment : Fragment() {
 
     private val adapter = GalleryAdapter()
     private val args: GalleryFragmentArgs by navArgs()
+    private var searchJob: Job? = null
     private val viewModel: GalleryViewModel by viewModels {
         InjectorUtils.provideGalleryViewModelFactory()
     }
@@ -48,9 +50,8 @@ class GalleryFragment : Fragment() {
         val binding = FragmentGalleryBinding.inflate(inflater, container, false)
         context ?: return binding.root
 
-        viewModel.searchPictures(args.plantName)
         binding.photoList.adapter = adapter
-        subscribeUi(adapter, binding.root)
+        search(args.plantName)
 
         binding.toolbar.setNavigationOnClickListener { view ->
             view.findNavController().navigateUp()
@@ -59,26 +60,13 @@ class GalleryFragment : Fragment() {
         return binding.root
     }
 
-    private fun subscribeUi(adapter: GalleryAdapter, rootView: View) {
-        viewModel.repoResult.observe(viewLifecycleOwner) { result ->
-            when (result) {
-                is UnsplashSearchResult.Success -> {
-                    showPlaceholder(result.data.results.isEmpty())
-                    adapter.submitList(result.data.results)
-                }
-                is UnsplashSearchResult.Error -> {
-                    Snackbar.make(
-                        rootView,
-                        "Error: ${result.error}",
-                        Snackbar.LENGTH_LONG
-                    ).show()
-                }
+    private fun search(query: String) {
+        // Make sure we cancel the previous job before creating a new one
+        searchJob?.cancel()
+        searchJob = lifecycleScope.launch {
+            viewModel.searchPictures(query).collectLatest {
+                adapter.submitData(it)
             }
         }
     }
-
-    // Show placeholder if the list of pictures is empty
-    private fun showPlaceholder(isListEmpty: Boolean) {
-        // TODO: implement this
-    }
 }
diff --git a/app/src/main/java/com/google/samples/apps/sunflower/PlantDetailFragment.kt b/app/src/main/java/com/google/samples/apps/sunflower/PlantDetailFragment.kt
@@ -133,7 +133,7 @@ class PlantDetailFragment : Fragment() {
                 getString(R.string.share_text_plant, plant.name)
             }
         }
-        val shareIntent = ShareCompat.IntentBuilder.from(activity)
+        val shareIntent = ShareCompat.IntentBuilder.from(requireActivity())
             .setText(shareText)
             .setType("text/plain")
             .createChooserIntent()

diff --git a/app/src/main/java/com/google/samples/apps/sunflower/adapters/GalleryAdapter.kt b/app/src/main/java/com/google/samples/apps/sunflower/adapters/GalleryAdapter.kt
@@ -20,8 +20,8 @@ import android.content.Intent
 import android.net.Uri
 import android.view.LayoutInflater
 import android.view.ViewGroup
+import androidx.paging.PagingDataAdapter
 import androidx.recyclerview.widget.DiffUtil
-import androidx.recyclerview.widget.ListAdapter
 import androidx.recyclerview.widget.RecyclerView
 import com.google.samples.apps.sunflower.GalleryFragment
 import com.google.samples.apps.sunflower.adapters.GalleryAdapter.GalleryViewHolder
@@ -32,7 +32,7 @@ import com.google.samples.apps.sunflower.databinding.ListItemPhotoBinding
  * Adapter for the [RecyclerView] in [GalleryFragment].
  */
 
-class GalleryAdapter : ListAdapter<UnsplashPhoto, GalleryViewHolder>(GalleryDiffCallback()) {
+class GalleryAdapter : PagingDataAdapter<UnsplashPhoto, GalleryViewHolder>(GalleryDiffCallback()) {
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): GalleryViewHolder {
         return GalleryViewHolder(ListItemPhotoBinding.inflate(
@@ -41,7 +41,9 @@ class GalleryAdapter : ListAdapter<UnsplashPhoto, GalleryViewHolder>(GalleryDiff
 
     override fun onBindViewHolder(holder: GalleryViewHolder, position: Int) {
         val photo = getItem(position)
-        holder.bind(photo)
+        if (photo != null) {
+            holder.bind(photo)
+        }
     }
 
     class GalleryViewHolder(

diff --git a/app/src/main/java/com/google/samples/apps/sunflower/api/UnsplashService.kt b/app/src/main/java/com/google/samples/apps/sunflower/api/UnsplashService.kt
@@ -34,9 +34,9 @@ interface UnsplashService {
     @GET("search/photos")
     suspend fun searchPhotos(
         @Query("query") query: String,
-        @Query("client_id") clientId: String = BuildConfig.UNSPLASH_ACCESS_KEY,
-        @Query("page") page: Int = 1,
-        @Query("per_page") perPage: Int = 20
+        @Query("page") page: Int,
+        @Query("per_page") perPage: Int,
+        @Query("client_id") clientId: String = BuildConfig.UNSPLASH_ACCESS_KEY
     ) : UnsplashSearchResponse
 
     companion object {

diff --git a/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashPagingSource.kt b/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashPagingSource.kt
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * 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.
+ */
+
+package com.google.samples.apps.sunflower.data
+
+import androidx.paging.PagingSource
+import com.google.samples.apps.sunflower.api.UnsplashService
+
+private const val UNSPLASH_STARTING_PAGE_INDEX = 1
+
+class UnsplashPagingSource (
+    private val service: UnsplashService,
+    private val query: String
+) : PagingSource<Int, UnsplashPhoto>() {
+
+    override suspend fun load(params: LoadParams<Int>): LoadResult<Int, UnsplashPhoto> {
+        val page = params.key ?: UNSPLASH_STARTING_PAGE_INDEX
+        return try {
+            val response = service.searchPhotos(query, page, params.loadSize)
+            val photos = response.results
+            LoadResult.Page(
+                data = photos,
+                prevKey = if (page == UNSPLASH_STARTING_PAGE_INDEX) null else page - 1,
+                nextKey = if (page == response.totalPages) null else page + 1
+            )
+        } catch (exception: Exception) {
+            LoadResult.Error(exception)
+        }
+    }
+}
diff --git a/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashRepository.kt b/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashRepository.kt
@@ -16,30 +16,22 @@
 
 package com.google.samples.apps.sunflower.data
 
+import androidx.paging.Pager
+import androidx.paging.PagingConfig
+import androidx.paging.PagingData
 import com.google.samples.apps.sunflower.api.UnsplashService
-import kotlinx.coroutines.channels.ConflatedBroadcastChannel
 import kotlinx.coroutines.flow.Flow
-import kotlinx.coroutines.flow.asFlow
-import retrofit2.HttpException
-import java.io.IOException
 
 class UnsplashRepository (private val service: UnsplashService) {
 
-    private val searchResult = ConflatedBroadcastChannel<UnsplashSearchResult>()
-
-    suspend fun getSearchResultStream(query: String): Flow<UnsplashSearchResult> {
-        requestData(query)
-        return searchResult.asFlow()
+    fun getSearchResultStream(query: String): Flow<PagingData<UnsplashPhoto>> {
+        return Pager(
+            config = PagingConfig(enablePlaceholders = false, pageSize = NETWORK_PAGE_SIZE),
+            pagingSourceFactory = { UnsplashPagingSource(service, query) }
+        ).flow
     }
 
-    private suspend fun requestData(query: String) {
-        try {
-            val response = service.searchPhotos(query)
-            searchResult.offer(UnsplashSearchResult.Success(response))
-        } catch (exception: IOException) {
-            searchResult.offer(UnsplashSearchResult.Error(exception))
-        } catch (exception: HttpException) {
-            searchResult.offer(UnsplashSearchResult.Error(exception))
-        }
+    companion object {
+        private const val NETWORK_PAGE_SIZE = 25
     }
 }
diff --git a/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashSearchResponse.kt b/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashSearchResponse.kt
@@ -26,5 +26,6 @@ import com.google.gson.annotations.SerializedName
  * [here](https://unsplash.com/documentation#search-photos).
  */
 data class UnsplashSearchResponse(
-    @field:SerializedName("results") val results: List<UnsplashPhoto>
+    @field:SerializedName("results") val results: List<UnsplashPhoto>,
+    @field:SerializedName("total_pages") val totalPages: Int
 )
diff --git a/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashSearchResult.kt b/app/src/main/java/com/google/samples/apps/sunflower/data/UnsplashSearchResult.kt
diff --git a/app/src/main/java/com/google/samples/apps/sunflower/viewmodels/GalleryViewModel.kt b/app/src/main/java/com/google/samples/apps/sunflower/viewmodels/GalleryViewModel.kt
@@ -16,30 +16,25 @@
 
 package com.google.samples.apps.sunflower.viewmodels
 
-import androidx.lifecycle.LiveData
-import androidx.lifecycle.MutableLiveData
 import androidx.lifecycle.ViewModel
-import androidx.lifecycle.asLiveData
-import androidx.lifecycle.liveData
-import androidx.lifecycle.switchMap
+import androidx.lifecycle.viewModelScope
+import androidx.paging.PagingData
+import androidx.paging.cachedIn
+import com.google.samples.apps.sunflower.data.UnsplashPhoto
 import com.google.samples.apps.sunflower.data.UnsplashRepository
-import com.google.samples.apps.sunflower.data.UnsplashSearchResult
-import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.Flow
 
 class GalleryViewModel internal constructor(
-    repository: UnsplashRepository
+    private val repository: UnsplashRepository
 ) : ViewModel() {
+    private var currentQueryValue: String? = null
+    private var currentSearchResult: Flow<PagingData<UnsplashPhoto>>? = null
 
-    private val queryLiveData = MutableLiveData<String>()
-
-    val repoResult: LiveData<UnsplashSearchResult> = queryLiveData.switchMap { queryString ->
-        liveData {
-            val repos = repository.getSearchResultStream(queryString).asLiveData()
-            emitSource(repos)
-        }
-    }
-
-    fun searchPictures(queryString: String) {
-        queryLiveData.postValue(queryString)
+    fun searchPictures(queryString: String): Flow<PagingData<UnsplashPhoto>> {
+        currentQueryValue = queryString
+        val newResult: Flow<PagingData<UnsplashPhoto>> =
+            repository.getSearchResultStream(queryString).cachedIn(viewModelScope)
+        currentSearchResult = newResult
+        return newResult
     }
 }
diff --git a/build.gradle b/build.gradle
@@ -40,7 +40,8 @@ buildscript {
         materialVersion = '1.1.0-alpha09'
         navigationVersion = '2.2.0'
         okhttpLoggingVersion = '4.7.2'
-        recyclerViewVersion = '1.1.0-alpha05'
+        pagingVersion = '3.0.0-alpha02'
+        recyclerViewVersion = '1.2.0-alpha04'
         retrofitVersion = '2.9.0'
         roomVersion = '2.1.0'
         runnerVersion = '1.0.1'