Improve performance of recycler views and prevent flickering on state change.

app/src/main/java/com/github/apognu/otter/adapters/AlbumsAdapter.kt

@@ -20,6 +20,8 @@ class AlbumsAdapter(val context: Context?, private val listener: OnAlbumClickLis
     fun onClick(view: View?, album: Album)
   }
 
+  override fun getItemId(position: Int): Long = data[position].id.toLong()
+
   override fun getItemCount() = data.size
 
   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {

app/src/main/java/com/github/apognu/otter/adapters/AlbumsGridAdapter.kt

@@ -19,6 +19,8 @@ class AlbumsGridAdapter(val context: Context?, private val listener: OnAlbumClic
     fun onClick(view: View?, album: Album)
   }
 
+  override fun getItemId(position: Int): Long = data[position].id.toLong()
+
   override fun getItemCount() = data.size
 
   override fun onCreateViewHolder(parent: ViewGroup, viewType: Int): ViewHolder {

app/src/main/java/com/github/apognu/otter/adapters/RadiosAdapter.kt

@@ -57,9 +57,13 @@ class RadiosAdapter(val context: Context?, val scope: CoroutineScope, private va
     }
   }
 
-  override fun getItemCount() = instanceRadios.size + data.size + 2
+  override fun getItemId(position: Int) = when (getItemViewType(position)) {
+    RowType.InstanceRadio.ordinal -> (-position - 1).toLong()
+    RowType.Header.ordinal -> Long.MIN_VALUE
+    else -> getRadioAt(position).id.toLong()
+  }
 
-  override fun getItemId(position: Int) = data[position].id.toLong()
+  override fun getItemCount() = instanceRadios.size + data.size + 2
 
   override fun getItemViewType(position: Int): Int {
     return when {

app/src/main/java/com/github/apognu/otter/adapters/TracksAdapter.kt

@@ -25,11 +25,9 @@ class TracksAdapter(private val context: Context?, private val favoriteListener:
 
   var currentTrack: Track? = null
 
-  override fun getItemCount() = data.size
+  override fun getItemId(position: Int): Long = data[position].id.toLong()
 
-  override fun getItemId(position: Int): Long {
-    return data[position].id.toLong()
-  }
+  override fun getItemCount() = data.size
 
   override fun onAttachedToRecyclerView(recyclerView: RecyclerView) {
     super.onAttachedToRecyclerView(recyclerView)

app/src/main/java/com/github/apognu/otter/fragments/OtterFragment.kt

@@ -8,6 +8,7 @@ import androidx.fragment.app.Fragment
 import androidx.lifecycle.lifecycleScope
 import androidx.recyclerview.widget.LinearLayoutManager
 import androidx.recyclerview.widget.RecyclerView
+import androidx.recyclerview.widget.SimpleItemAnimator
 import com.github.apognu.otter.repositories.HttpUpstream
 import com.github.apognu.otter.repositories.Repository
 import com.github.apognu.otter.utils.*
@@ -22,6 +23,12 @@ import kotlinx.coroutines.withContext
 
 abstract class OtterAdapter<D, VH : RecyclerView.ViewHolder> : RecyclerView.Adapter<VH>() {
   var data: MutableList<D> = mutableListOf()
+
+  init {
+    super.setHasStableIds(true)
+  }
+
+  abstract override fun getItemId(position: Int): Long
 }
 
 abstract class OtterFragment<D : Any, A : OtterAdapter<D, *>> : Fragment() {
@@ -46,6 +53,7 @@ abstract class OtterFragment<D : Any, A : OtterAdapter<D, *>> : Fragment() {
     super.onViewCreated(view, savedInstanceState)
 
     recycler.layoutManager = layoutManager
+    (recycler.itemAnimator as? SimpleItemAnimator)?.supportsChangeAnimations = false
     recycler.adapter = adapter
 
     (repository.upstream as? HttpUpstream<*, *>)?.let { upstream ->