Step 3 - Add separators every 10k stars

app/src/main/java/com/example/android/codelabs/paging/api/RepoSearchResponse.kt

@@ -23,7 +23,7 @@ import com.google.gson.annotations.SerializedName
  * Data class to hold repo responses from searchRepo API calls.
  */
 data class RepoSearchResponse(
-    @SerializedName("total_count") val total: Int = 0,
-    @SerializedName("items") val items: List<Repo> = emptyList(),
-    val nextPage: Int? = null
-)
+        @SerializedName("total_count") val total: Int = 0,
+        @SerializedName("items") val items: List<Repo> = emptyList(),
+        val nextPage: Int? = null
+)

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

@@ -21,28 +21,49 @@ import androidx.paging.PagingDataAdapter
 import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView.ViewHolder
 import com.example.android.codelabs.paging.R
-import com.example.android.codelabs.paging.model.Repo
+import java.lang.UnsupportedOperationException
 
 /**
  * Adapter for the list of repositories.
  */
-class ReposAdapter : PagingDataAdapter<Repo, ViewHolder>(REPO_COMPARATOR) {
+class ReposAdapter : PagingDataAdapter<UiModel, ViewHolder>(UIMODEL_COMPARATOR) {
 
     override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {
-        return RepoViewHolder.create(parent)
+        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 -> throw UnsupportedOperationException("Unknown view")
+        }
     }
 
     override fun onBindViewHolder(holder: ViewHolder, position: Int) {
-        val repo = getItem(position)
-        (holder as RepoViewHolder).bind(repo)
+        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 (oldItem is UiModel.RepoItem && newItem is UiModel.RepoItem &&
+                        oldItem.repo.fullName == newItem.repo.fullName) ||
+                        (oldItem is UiModel.SeparatorItem && newItem is UiModel.SeparatorItem &&
+                                oldItem.description == newItem.description)
+            }
 
-            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/ReposLoadStateViewHolder.kt

@@ -62,3 +62,4 @@ class ReposLoadStateViewHolder(
         }
     }
 }
+

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

@@ -77,7 +77,7 @@ class SearchRepositoriesActivity : AppCompatActivity() {
         adapter.addLoadStateListener { loadType, loadState ->
             Log.d("SearchRepositoriesActivity", "adapter load: type = $loadType state = $loadState")
             if (loadType == LoadType.REFRESH) {
-                binding.list.visibility = View.GONE
+                binding.list.visibility = toVisibility(loadState == LoadState.Idle)
                 binding.progressBar.visibility = toVisibility(loadState == LoadState.Loading)
                 binding.retryButton.visibility = toVisibility(loadState is LoadState.Error)
             } else {

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

@@ -16,14 +16,17 @@
 
 package com.example.android.codelabs.paging.ui
 
+import android.util.Log
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import androidx.paging.PagingData
 import androidx.paging.cachedIn
+import androidx.paging.insertSeparators
 import com.example.android.codelabs.paging.data.GithubRepository
 import com.example.android.codelabs.paging.model.Repo
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.map
 
 /**
  * ViewModel for the [SearchRepositoriesActivity] screen.
@@ -36,20 +39,46 @@ class SearchRepositoriesViewModel(private val repository: GithubRepository) : Vi
     private var currentQueryValue: String? = null
 
     @Volatile
-    private var currentSearchResult: Flow<PagingData<Repo>>? = null
+    private var currentSearchResult: Flow<PagingData<UiModel>>? = null
 
     /**
      * Search a repository based on a query string.
      */
-    fun searchRepo(queryString: String): Flow<PagingData<Repo>> {
+    fun searchRepo(queryString: String): Flow<PagingData<UiModel>> {
         val lastResult = currentSearchResult
         if (queryString == currentQueryValue && lastResult != null) {
             return lastResult
         }
         currentQueryValue = queryString
-        val newResult: Flow<PagingData<Repo>> = repository.getSearchResultStream(queryString)
+        val newResult: Flow<PagingData<UiModel>> = repository.getSearchResultStream(queryString)
+                .map { pagingData -> pagingData.map { UiModel.RepoItem(it) } }
+                .map {
+                    it.insertSeparators<UiModel.RepoItem, UiModel> { before, after ->
+                        if (before == null && after != null) {
+                            UiModel.SeparatorItem("${after.roundedStarCount}0.000+ stars")
+                        } else if (before != null && after != null
+                                && before.roundedStarCount > after.roundedStarCount) {
+                            if (after.roundedStarCount >= 1) {
+                                UiModel.SeparatorItem("${after.roundedStarCount}0.000+ stars")
+                            } else {
+                                UiModel.SeparatorItem("< 10.000+ stars")
+                            }
+                        } else {
+                            // no separator
+                            null
+                        }
+                    }
+                }
                 .cachedIn(viewModelScope)
         currentSearchResult = newResult
         return newResult
     }
 }
+
+sealed class UiModel {
+    data class RepoItem(val repo: Repo) : UiModel()
+    data class SeparatorItem(val description: String) : UiModel()
+}
+
+private val UiModel.RepoItem.roundedStarCount: Int
+    get() = this.repo.stars / 10_000

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

@@ -0,0 +1,40 @@
+/*
+ * 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.ui
+
+import android.view.LayoutInflater
+import android.view.View
+import android.view.ViewGroup
+import android.widget.TextView
+import androidx.recyclerview.widget.RecyclerView
+import com.example.android.codelabs.paging.R
+
+class SeparatorViewHolder(view: View) : RecyclerView.ViewHolder(view) {
+    private val description: TextView = view.findViewById(R.id.separator_description)
+
+    fun bind(separatorText: String) {
+        description.text = separatorText
+    }
+
+    companion object {
+        fun create(parent: ViewGroup): SeparatorViewHolder {
+            val view = LayoutInflater.from(parent.context)
+                    .inflate(R.layout.separator_view_item, parent, false)
+            return SeparatorViewHolder(view)
+        }
+    }
+}

app/src/main/res/layout/separator_view_item.xml

@@ -0,0 +1,34 @@
+<?xml version="1.0" encoding="utf-8"?><!--
+  ~ 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.
+  -->
+<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="@color/separatorBackground">
+
+    <TextView
+        android:id="@+id/separator_description"
+        android:layout_width="0dp"
+        android:layout_height="wrap_content"
+        android:padding="@dimen/row_item_margin_horizontal"
+        android:textColor="@color/separatorText"
+        android:textSize="@dimen/repo_name_size"
+        app:layout_constraintEnd_toEndOf="parent"
+        app:layout_constraintStart_toStartOf="parent"
+        app:layout_constraintTop_toTopOf="parent"
+        tools:text="10000+ stars" />
+</androidx.constraintlayout.widget.ConstraintLayout>