Refactor recycler view adapters to use Flexible adapter and drop SectionnedRecyclerViewAdapter

- Fixes #51: Unread subscription time groups are not time-sorted
- Fixes #50: Categories are not alphabetically sorted
- Implments #54: Add fast scroller bar with section display

CHANGELOG.md

 # Development
 
+## Features
+
+* Implements [#54](https://git.feneas.org/christophehenry/freshrss-android/issues/54): Add fast scroller bar with section display ([!17](https://git.feneas.org/christophehenry/freshrss-android/merge_requests/17))
+
+## Bug fixes
+
+* [#50](https://git.feneas.org/christophehenry/freshrss-android/issues/50): Categories are not alphabetically sorted
+* [#51](https://git.feneas.org/christophehenry/freshrss-android/issues/51): Unread subscription time groups are not time-sorted
+
 # 1.1.0
 
 ## Features
@@ -18,7 +27,7 @@
 
 * Fix service lately binded to application causing stacktrace ([a58c00dd](https://git.feneas.org/christophehenry/freshrss-android/commit/a58c00dd8c8c6e292a0210a64a38238b253978a4))
 * Fix loader displaying infinitely when a subscription section stays empty after refresh by displaying a hint text stating section is empty ([13b7c02c](https://git.feneas.org/christophehenry/freshrss-android/commit/13b7c02c28bfdfd543de668006dff161330e3b75))
-* Fix [#38](https://git.feneas.org/christophehenry/freshrss-android/issues/38]: empty screen when going back from the initial screen ([4f84e6b5](https://git.feneas.org/christophehenry/freshrss-android/commit/4f84e6b5f6de7d42a24d541e099a402d034792da))
+* Fix [#38](<https://git.feneas.org/christophehenry/freshrss-android/issues/38>]: empty screen when going back from the initial screen ([4f84e6b5](https://git.feneas.org/christophehenry/freshrss-android/commit/4f84e6b5f6de7d42a24d541e099a402d034792da))
 * Fix [#13](https://git.feneas.org/christophehenry/freshrss-android/issues/13) and [#14](https://git.feneas.org/christophehenry/freshrss-android/issues/14): erratic notification behavior ([0c1b5e76](https://git.feneas.org/christophehenry/freshrss-android/commit/0c1b5e7600888d905f67dc28b0389229b52b67f7))
 * Fix crash hapening when object is returned from `unread-counts` endpoint without `newestItemTimestampUsec` property ([8cfcd932](https://git.feneas.org/christophehenry/freshrss-android/commit/8cfcd932619b601371b6f0d0a4bcb7d4b92ce3dd))
 * Fix spinner infinitely loading when comming back from a feed with a single unread article ([3088922f](https://git.feneas.org/christophehenry/freshrss-android/commit/3088922f9405ee173d6a6cb81b8868a35759aedd))

app/build.gradle

@@ -125,8 +125,10 @@ dependencies {
     implementation "org.apache.commons:commons-text:1.4"
     implementation "joda-time:joda-time:2.10.1"
     implementation "com.squareup.picasso:picasso:2.71828"
-    implementation "io.github.luizgrp.sectionedrecyclerviewadapter:sectionedrecyclerviewadapter:2.0.0"
     implementation "com.x5dev:chunk-templates:3.4.0"
+    implementation "eu.davidea:flexible-adapter:5.1.0"
+    implementation "eu.davidea:flexible-adapter-ui:1.0.0"
+
 
     // Tests
     testImplementation "junit:junit:4.12"

app/src/main/java/fr/chenry/android/freshrss/RefresherService.kt

@@ -5,6 +5,8 @@ import android.app.Service
 import android.content.Intent
 import android.os.Binder
 import androidx.core.app.NotificationCompat
+import androidx.lifecycle.LiveData
+import androidx.lifecycle.MutableLiveData
 import fr.chenry.android.freshrss.store.Store
 import fr.chenry.android.freshrss.utils.NotificationChanels
 import fr.chenry.android.freshrss.utils.NotificationHelper

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/MainSubscriptionFragment.kt

@@ -16,6 +16,7 @@ import fr.chenry.android.freshrss.store.Store
 import fr.chenry.android.freshrss.store.database.models.VoidCategory
 import fr.chenry.android.freshrss.utils.whenNotNull
 import kotlinx.android.synthetic.main.fragment_main_subscription.*
+import kotlinx.android.synthetic.main.fragment_subscriptions.*
 import kotlinx.android.synthetic.main.menu_badge.*
 import nl.komponents.kovenant.ui.alwaysUi
 
@@ -30,12 +31,6 @@ class MainSubscriptionFragment: Fragment(), BottomNavigationView.OnNavigationIte
 
         setupBadgeCount()
 
-        subcription_pull_to_refresh.setOnRefreshListener {
-            FreshRSSApplication.application.refresherService.value.whenNotNull {
-                it.refresh().alwaysUi {subcription_pull_to_refresh.isRefreshing = false}
-            }
-        }
-
         subcription_fragment_container.adapter = adapter
         subcription_fragment_container.offscreenPageLimit = SubscriptionSection.values().size
 

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/RecyclerViewAdapter.kt

-package fr.chenry.android.freshrss.components.subscriptions
-
-import android.view.View
-import android.widget.TextView
-import androidx.databinding.DataBindingUtil
-import androidx.lifecycle.Observer
-import androidx.recyclerview.widget.*
-import fr.chenry.android.freshrss.*
-import fr.chenry.android.freshrss.R
-import fr.chenry.android.freshrss.databinding.FragmentSubscriptionBinding
-import fr.chenry.android.freshrss.store.database.models.*
-import io.github.luizgrp.sectionedrecyclerviewadapter.*
-
-class RecyclerViewAdapter(private val fragment: SubscriptionsFragment): SectionedRecyclerViewAdapter() {
-    private val categorySectionTag = Char.MIN_VALUE.toString()
-
-    init {
-        addSection(categorySectionTag, RecyclerViewAdapterSection2(listOf()))
-
-        fragment.model.sectionnedLiveData.observe(fragment, Observer {
-            it.entries.forEach {self ->
-                if(getSection(self.key) == null) addSection(self.key, RecyclerViewAdapterSection(self.key, self.value))
-                else {
-                    val oldItems: Subscriptions = getSection(self.key)
-                        ?.let {s ->
-                            s as RecyclerViewAdapterSection
-                            val result = s.subscriptions
-                            s.subscriptions = it[self.key] ?: listOf()
-                            result
-                        } ?: listOf()
-
-                    val newItems: Subscriptions = it[self.key] ?: oldItems
-
-                    DiffUtil
-                        .calculateDiff(SectionDiffUtilsCallback(oldItems, newItems))
-                        .dispatchUpdatesTo(SectionUpdateCallback(self.key))
-                }
-            }
-        })
-
-        fragment.model.subscriptionCategoriesLiveData.observe(fragment, Observer {
-            val oldItems = getSection(categorySectionTag)
-                ?.let {s ->
-                    s as RecyclerViewAdapterSection2
-                    val result = s.subscriptionCategories
-                    s.subscriptionCategories = it
-                    result
-                } ?: listOf()
-
-            if(getSection(categorySectionTag).hasHeader() != it.isNotEmpty()) {
-                getSection(categorySectionTag).setHasHeader(it.isNotEmpty())
-                if(it.isNotEmpty()) notifyHeaderInsertedInSection(categorySectionTag)
-                else notifyHeaderRemovedFromSection(categorySectionTag)
-            }
-
-            DiffUtil
-                .calculateDiff(SectionDiffUtilsCallback(oldItems, it))
-                .dispatchUpdatesTo(SectionUpdateCallback(categorySectionTag))
-        })
-    }
-
-    inner class ViewHolder(val binding: FragmentSubscriptionBinding): RecyclerView.ViewHolder(binding.root) {
-        fun bind(subscription: Subscription) {
-            binding.setVariable(BR.subscription, subscription)
-            binding.executePendingBindings()
-        }
-    }
-
-    inner class RecyclerViewAdapterSection(private val sectionTag: String, var subscriptions: Subscriptions):
-        StatelessSection(getSectionParameters()) {
-        override fun onBindItemViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
-            val subscription = subscriptions[position]
-            (holder as ViewHolder).apply {
-                bind(subscription)
-                binding.root.setOnClickListener {fragment.onClick(subscription)}
-            }
-        }
-
-        override fun onBindHeaderViewHolder(holder: RecyclerView.ViewHolder) {
-            holder.itemView.findViewById<TextView>(R.id.subscription_section_header_title).text = sectionTag
-        }
-
-        override fun getItemViewHolder(view: View) = ViewHolder(DataBindingUtil.bind(view)!!)
-        override fun getContentItemsTotal() = subscriptions.size
-    }
-
-    inner class RecyclerViewAdapterSection2(var subscriptionCategories: SubscriptionCategories):
-        StatelessSection(getSectionParameters()) {
-        override fun onBindItemViewHolder(holder: RecyclerView.ViewHolder, position: Int) {
-            val subscriptionCategory = subscriptionCategories[position]
-            (holder as ViewHolder).apply {
-                bind(Subscription("", subscriptionCategory.label, "", -1, listOf()))
-                binding.root.setOnClickListener {fragment.onClick(subscriptionCategory)}
-            }
-        }
-
-        override fun onBindHeaderViewHolder(holder: RecyclerView.ViewHolder) {
-            holder.itemView.findViewById<TextView>(R.id.subscription_section_header_title).text =
-                FreshRSSApplication.getStringR(R.string.subscription_categories)
-        }
-
-        override fun getItemViewHolder(view: View) = ViewHolder(DataBindingUtil.bind(view)!!)
-        override fun getContentItemsTotal() = subscriptionCategories.size
-    }
-
-    inner class SectionUpdateCallback(private val sectionTag: String): ListUpdateCallback {
-        override fun onChanged(position: Int, count: Int, payload: Any?) =
-            notifyItemChangedInSection(sectionTag, position)
-
-        override fun onMoved(fromPosition: Int, toPosition: Int) =
-            notifyItemMovedInSection(sectionTag, fromPosition, toPosition)
-
-        override fun onInserted(position: Int, count: Int) = notifyItemInsertedInSection(sectionTag, position)
-        override fun onRemoved(position: Int, count: Int) = notifyItemRemovedFromSection(sectionTag, position)
-
-    }
-
-    inner class SectionDiffUtilsCallback<T>(private val oldItems: List<T>, private val newItems: List<T>):
-        DiffUtil.Callback() {
-        override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
-            val oldItem = oldItems.getOrNull(oldItemPosition)
-            val newitem = newItems.getOrNull(newItemPosition)
-            return oldItem != null && newitem != null && oldItem.hashCode() == newitem.hashCode()
-        }
-
-        override fun getOldListSize() = oldItems.size
-        override fun getNewListSize() = newItems.size
-        override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean =
-            oldItems.getOrNull(oldItemPosition)?.equals(newItems.getOrNull(newItemPosition)) ?: false
-    }
-
-    companion object {
-        fun getSectionParameters(): SectionParameters =
-            SectionParameters.builder()
-                .headerResourceId(R.layout.fragment_subscription_header)
-                .itemResourceId(R.layout.fragment_subscription)
-                .build()
-    }
-}

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/SubscriptionsFragment.kt

@@ -10,18 +10,25 @@ import androidx.navigation.fragment.findNavController
 import androidx.navigation.fragment.navArgs
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import androidx.swiperefreshlayout.widget.SwipeRefreshLayout
+import eu.davidea.fastscroller.FastScroller
 import fr.chenry.android.freshrss.*
 import fr.chenry.android.freshrss.components.subscriptions.SubscriptionSection.*
+import fr.chenry.android.freshrss.components.subscriptions.adapters.SubscriptionsFlexibleAdapter
 import fr.chenry.android.freshrss.store.Store
 import fr.chenry.android.freshrss.store.database.models.*
 import fr.chenry.android.freshrss.store.database.models.ReadStatus.READ
 import fr.chenry.android.freshrss.store.viewmodels.*
+import fr.chenry.android.freshrss.utils.whenNotNull
+import kotlinx.android.synthetic.main.fast_scroller.*
 import kotlinx.android.synthetic.main.fragment_subscriptions.*
+import nl.komponents.kovenant.Promise
 
 class SubscriptionsFragment: Fragment(), Observer<Subscriptions> {
     private val args: SubscriptionsFragmentArgs by navArgs()
     private val section by lazy {args.section}
     private val category by lazy {args.category}
+    private val adapter by lazy {SubscriptionsFlexibleAdapter(this)}
 
     val model by lazy {
         if(category != VoidCategory)
@@ -35,17 +42,21 @@ class SubscriptionsFragment: Fragment(), Observer<Subscriptions> {
         }
     }
 
-    private val adapter by lazy {RecyclerViewAdapter(this)}
-
     override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
         val view = inflater.inflate(R.layout.fragment_subscriptions, container, false)
 
         Store.refreshingPromise.observe(this, Observer {toggleProgressCircle(model.liveData.value ?: listOf())})
         model.liveData.observe(this, this)
 
-        view.findViewById<RecyclerView>(R.id.subscriptions_list).let {
+        view.findViewById<RecyclerView>(R.id.fragment_subscriptions_list).let {
             it.layoutManager = LinearLayoutManager(context, RecyclerView.VERTICAL, false)
-            it.adapter = this.adapter
+            it.adapter = adapter
+            it.addOnLayoutChangeListener { _, _, top, _, bottom, _, oldTop, _, oldBottom ->
+                if(top == oldTop && bottom == oldBottom) return@addOnLayoutChangeListener
+                fast_scroller.visibility =
+                    if(fragment_subscriptions_list.height >= fragment_subscriptions_list_container.height) View.VISIBLE
+                    else View.GONE
+            }
         }
 
         val contentDescription = if(category != VoidCategory)
@@ -59,16 +70,25 @@ class SubscriptionsFragment: Fragment(), Observer<Subscriptions> {
         view.findViewById<TextView>(R.id.fragment_subscriptions_empty_list).text =
             FreshRSSApplication.getStringR(R.string.empty_subscription_section_template, contentDescription)
 
-        return view
-    }
+        view.findViewById<FastScroller>(R.id.fast_scroller).let {
+            it.isAutoHideEnabled = false
+            adapter.fastScroller = it
+        }
 
-    override fun onChanged(subscriptions: Subscriptions?) {
-        (subscriptions ?: listOf()).let {
-            toggleProgressCircle(it)
-            adapter.notifyDataSetChanged()
+        view.findViewById<SwipeRefreshLayout>(R.id.subcription_pull_to_refresh)?.let {
+            Store.refreshingPromise.observe(this, Observer<Promise<Unit, Exception>?> {v ->
+                it.isRefreshing = v != null
+            })
+            it.setOnRefreshListener {
+                FreshRSSApplication.application.refresherService.value.whenNotNull {rs -> rs.refresh()}
+            }
         }
+
+        return view
     }
 
+    override fun onChanged(subscriptions: Subscriptions?) = toggleProgressCircle((subscriptions ?: listOf()))
+
     fun onClick(subscription: Subscription) = when(section) {
         FAVORITES -> MainNavDirections.actionGlobalSubscriptionArticlesFragment(subscription.id, READ)
         ALL -> MainNavDirections.actionGlobalSubscriptionArticlesFragment(subscription.id, READ)
@@ -81,11 +101,13 @@ class SubscriptionsFragment: Fragment(), Observer<Subscriptions> {
 
     private fun toggleProgressCircle(subscriptions: Subscriptions) {
         if(Store.refreshingPromise.value == null) {
-            subscriptions_list.visibility = if(subscriptions.isNotEmpty()) View.VISIBLE else View.GONE
+            fragment_subscriptions_list_container.visibility =
+                if(subscriptions.isNotEmpty()) View.VISIBLE else View.GONE
             fragment_subscriptions_empty_list.visibility = if(subscriptions.isEmpty()) View.VISIBLE else View.GONE
             fragment_subscriptions_waiting.visibility = View.GONE
         } else {
-            subscriptions_list.visibility = if(subscriptions.isNotEmpty()) View.VISIBLE else View.GONE
+            fragment_subscriptions_list_container.visibility =
+                if(subscriptions.isNotEmpty()) View.VISIBLE else View.GONE
             fragment_subscriptions_waiting.visibility = if(subscriptions.isEmpty()) View.VISIBLE else View.GONE
             fragment_subscriptions_empty_list.visibility = View.GONE
         }

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/adapters/AbstractSubscriptionViewItem.kt

+package fr.chenry.android.freshrss.components.subscriptions.adapters
+
+import android.view.View
+import androidx.databinding.DataBindingUtil
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+import eu.davidea.flexibleadapter.FlexibleAdapter
+import eu.davidea.flexibleadapter.items.AbstractSectionableItem
+import eu.davidea.flexibleadapter.items.IFlexible
+import eu.davidea.viewholders.FlexibleViewHolder
+import fr.chenry.android.freshrss.BR
+import fr.chenry.android.freshrss.R
+import fr.chenry.android.freshrss.components.subscriptions.adapters.AbstractSubscriptionViewItem.SubscriptionViewHolder
+import fr.chenry.android.freshrss.databinding.FragmentSubscriptionBinding
+import fr.chenry.android.freshrss.store.database.models.Subscription
+import fr.chenry.android.freshrss.store.database.models.SubscriptionCategory
+
+sealed class AbstractSubscriptionViewItem(header: SubscriptionViewHeaderItem):
+    AbstractSectionableItem<SubscriptionViewHolder, SubscriptionViewHeaderItem>(header) {
+    abstract val virtualSubscription: Subscription
+
+    init {
+        isDraggable = false
+        isSelectable = false
+        isSwipeable = false
+    }
+
+    override fun createViewHolder(
+        view: View?,
+        adapter: FlexibleAdapter<IFlexible<ViewHolder>>?
+    ): SubscriptionViewHolder = SubscriptionViewHolder(DataBindingUtil.bind(view!!)!!, adapter)
+
+    override fun bindViewHolder(
+        adapter: FlexibleAdapter<IFlexible<ViewHolder>>?,
+        holder: SubscriptionViewHolder?, position: Int,
+        payloads: MutableList<Any>?
+    ) = holder?.bind(virtualSubscription).let {Unit}
+
+    override fun getLayoutRes() = R.layout.fragment_subscription
+
+    inner class SubscriptionViewHolder(
+        private val binding: FragmentSubscriptionBinding,
+        adapter: FlexibleAdapter<IFlexible<ViewHolder>>?
+    ): FlexibleViewHolder(binding.root, adapter) {
+        fun bind(subscription: Subscription) {
+            binding.setVariable(BR.subscription, subscription)
+            binding.executePendingBindings()
+        }
+    }
+}
+
+class SubscriptionViewItem(val subscription: Subscription, header: String):
+    AbstractSubscriptionViewItem(SubscriptionViewHeaderItem(header)) {
+    override val virtualSubscription: Subscription get() = subscription
+
+    override fun equals(other: Any?): Boolean =
+        if(other !is SubscriptionViewItem) false else subscription == other.subscription
+
+    override fun hashCode(): Int = subscription.hashCode()
+}
+
+class SubscriptionCategoryViewItem(val subscriptionCategory: SubscriptionCategory):
+    AbstractSubscriptionViewItem(SubscriptionCategoryViewHeaderItem) {
+    override val virtualSubscription: Subscription =
+        Subscription(subscriptionCategory.id, subscriptionCategory.label, "", unreadCount = -1)
+
+    override fun equals(other: Any?): Boolean =
+        if(other !is SubscriptionCategoryViewItem) false else subscriptionCategory == other.subscriptionCategory
+
+    override fun hashCode(): Int = subscriptionCategory.hashCode()
+}
\ No newline at end of file

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/adapters/SubscriptionViewHeaderItem.kt

+package fr.chenry.android.freshrss.components.subscriptions.adapters
+
+import android.view.View
+import android.widget.TextView
+import androidx.recyclerview.widget.RecyclerView.ViewHolder
+import eu.davidea.flexibleadapter.FlexibleAdapter
+import eu.davidea.flexibleadapter.items.AbstractHeaderItem
+import eu.davidea.flexibleadapter.items.IFlexible
+import eu.davidea.viewholders.FlexibleViewHolder
+import fr.chenry.android.freshrss.FreshRSSApplication
+import fr.chenry.android.freshrss.R
+
+open class SubscriptionViewHeaderItem(val title: String):
+    AbstractHeaderItem<SubscriptionViewHeaderItem.SubscriptionViewHeaderHolder>() {
+    init {
+        isDraggable = false
+        isSelectable = false
+        isSwipeable = false
+    }
+
+    override fun bindViewHolder(
+        adapter: FlexibleAdapter<IFlexible<ViewHolder>>?,
+        holder: SubscriptionViewHeaderHolder,
+        position: Int,
+        payloads: MutableList<Any>?
+    ) = holder.bind(title)
+
+    override fun createViewHolder(view: View?, adapter: FlexibleAdapter<IFlexible<ViewHolder>>?):
+        SubscriptionViewHeaderHolder =
+        SubscriptionViewHeaderHolder(view!!, adapter)
+
+    override fun getLayoutRes(): Int = R.layout.fragment_subscription_header
+
+    override fun equals(other: Any?): Boolean =
+        if(other !is SubscriptionViewHeaderItem) false else title == other.title
+
+    override fun hashCode(): Int = title.hashCode()
+
+    inner class SubscriptionViewHeaderHolder(
+        val view: View,
+        adapter: FlexibleAdapter<IFlexible<ViewHolder>>?
+    ): FlexibleViewHolder(view, adapter, true) {
+        fun bind(header: String) {
+            view.findViewById<TextView>(R.id.subscription_section_header_title).text = header
+        }
+    }
+}
+
+
+object SubscriptionCategoryViewHeaderItem:
+    SubscriptionViewHeaderItem(FreshRSSApplication.getStringR(R.string.subscription_categories))
\ No newline at end of file

app/src/main/java/fr/chenry/android/freshrss/components/subscriptions/adapters/SubscriptionsFlexibleAdapter.kt

+package fr.chenry.android.freshrss.components.subscriptions.adapters
+
+import android.view.View
+import androidx.lifecycle.MediatorLiveData
+import androidx.lifecycle.Observer
+import eu.davidea.flexibleadapter.FlexibleAdapter
+import eu.davidea.flexibleadapter.FlexibleAdapter.OnItemClickListener
+import eu.davidea.flexibleadapter.items.IFlexible
+import fr.chenry.android.freshrss.components.subscriptions.SubscriptionsFragment
+import fr.chenry.android.freshrss.store.database.models.*
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.task
+
+class SubscriptionsFlexibleAdapter(private val fragment: SubscriptionsFragment):
+    FlexibleAdapter<AbstractSubscriptionViewItem>(initFlexAdapter(fragment)), OnItemClickListener {
+    private val mediator = MediatorLiveData<List<AbstractSubscriptionViewItem>>()
+    private val subscriptionCategories
+        get() = fragment.model.subscriptionCategoriesLiveData.value ?: listOf()
+    private val subscriptions
+        get() = fragment.model.liveData.value ?: listOf()
+    private val grouper get() = fragment.model.grouper
+
+    init {
+        setStickyHeaders(true)
+        setDisplayHeadersAtStartUp(true)
+        mediator.observe(fragment, Observer {updateDataSet(it)})
+        mediator.addSource(fragment.model.liveData) {
+            computeNewDataSet(it, subscriptionCategories) success {res -> mediator.postValue(res)}
+        }
+        mediator.addSource(fragment.model.subscriptionCategoriesLiveData) {
+            computeNewDataSet(subscriptions, it) success {res -> mediator.postValue(res)}
+        }
+        addListener(this)
+    }
+
+    override fun isEmpty(): Boolean = fragment.model.liveData.value.isNullOrEmpty()
+
+    override fun onCreateBubbleText(position: Int): String? {
+        val item = getGenericItem(position)
+        return when(item) {
+            is AbstractSubscriptionViewItem -> item.header.title
+            is SubscriptionViewHeaderItem -> item.title
+            else -> null
+        }
+    }
+
+    override fun onItemClick(view: View?, position: Int): Boolean = getGenericItem(position)?.let {
+        when(it) {
+            is SubscriptionViewItem -> fragment.onClick(it.subscription)
+            is SubscriptionCategoryViewItem -> fragment.onClick(it.subscriptionCategory)
+        }
+        true
+    } ?: false
+
+    // This is probably one of the stupidest API design I've ever met
+    // This is actually known and the author refuses to fix
+    // WTF: https://github.com/davideas/FlexibleAdapter/issues/604
+    private fun getGenericItem(position: Int): IFlexible<*>? = (this as FlexibleAdapter<*>).getItem(position)
+
+    private fun computeNewDataSet(
+        subscriptions: Subscriptions,
+        subscriptionCategories: SubscriptionCategories
+    ): Promise<ArrayList<AbstractSubscriptionViewItem>, Exception> = task {
+        val targetSize = subscriptionCategories.size + subscriptions.size
+        val result = ArrayList<AbstractSubscriptionViewItem>(targetSize)
+        (0 until targetSize).forEach {
+            val newElt = if(it < subscriptionCategories.size)
+                SubscriptionCategoryViewItem(subscriptionCategories[it]) else
+                SubscriptionViewItem(
+                    subscriptions[it - subscriptionCategories.size],
+                    grouper(subscriptions[it - subscriptionCategories.size])
+                )
+
+            result.add(newElt)
+        }
+
+        result
+    }
+
+    companion object {
+        private fun initFlexAdapter(fragment: SubscriptionsFragment) =
+            getSubscriptionViewItems(fragment.model.liveData.value ?: listOf(), fragment.model.grouper)
+
+        private fun getSubscriptionViewItems(subscriptions: Subscriptions, grouper: (Subscription) -> String) =
+            subscriptions.map {SubscriptionViewItem(it, grouper(it))}
+    }
+}

app/src/main/java/fr/chenry/android/freshrss/store/viewmodels/SubscriptionsVM.kt

@@ -9,28 +9,21 @@ import fr.chenry.android.freshrss.store.database.models.*
 import org.joda.time.LocalDateTime
 
 sealed class SubscriptionsVM: ViewModel() {
-    abstract val subscriptionsLiveData: LiveData<Subscriptions>
     abstract val subscriptionCategoriesLiveData: LiveData<SubscriptionCategories>
-    abstract val comparator: Comparator<Subscription>
     abstract val grouper: (Subscription) -> String
 
+    protected abstract val comparator: Comparator<Subscription>
+    protected abstract val subscriptionsLiveData: LiveData<Subscriptions>
+
     val liveData: LiveData<Subscriptions> by lazy {
         MutableLiveData<Subscriptions>().apply {
-            value = load()
-            subscriptionsLiveData.observeForever {value = load()}
-        }
-    }
-
-    val sectionnedLiveData: LiveData<Map<String, Subscriptions>> by lazy {
-        MutableLiveData<Map<String, Subscriptions>>().apply {
-            liveData.observeForever {value = groupBy(it)}
+            value = (subscriptionsLiveData.value ?: listOf()).sortedWith(comparator)
+            subscriptionsLiveData.observeForever {value = it.sortedWith(comparator)}
         }
     }
 
-    private fun groupBy(subscriptions: Subscriptions): Map<String, Subscriptions> = subscriptions.groupBy(grouper)
-    private fun load(): Subscriptions = subscriptionsLiveData.value?.sortedWith(comparator) ?: listOf()
-
     companion object {
+        val labelComparator = Comparator<SubscriptionCategory> {o1, o2 -> o1.label.compareTo(o2.label, true)}
         val titleComparator = Comparator<Subscription> {o1, o2 -> o1.title.compareTo(o2.title, true)}
         val dateComparator = Comparator<Subscription> {o1, o2 ->
             if(o1.newestArticleDate.isEqual(o2.newestArticleDate))
@@ -58,9 +51,21 @@ class AllSubscriptionsVM: SubscriptionsVM() {
     override val comparator: Comparator<Subscription> get() = titleComparator
     override val grouper: (Subscription) -> String get() = titleGrouper
     override val subscriptionsLiveData = FreshRSSApplication.database.getAllSubcriptions().toLiveData()
-    override val subscriptionCategoriesLiveData by lazy {
-        FreshRSSApplication.database.getAllCategories().toLiveData()
+    override val subscriptionCategoriesLiveData: LiveData<SubscriptionCategories>
+
+    private val _subscriptionCategoriesLiveData: LiveData<SubscriptionCategories>
+
+    init {
+        val flowable = FreshRSSApplication.database.getAllCategories()
+        _subscriptionCategoriesLiveData = flowable.toLiveData()
+        subscriptionCategoriesLiveData = MutableLiveData<SubscriptionCategories>().apply {
+            value = flowable.blockingFirst().orEmpty().sortedWith(labelComparator)
+        }
+        _subscriptionCategoriesLiveData.observeForever {