Improve Session UI

app/src/main/java/net/pokeranalytics/android/ui/adapter/components/RowRepresentableAdapter.kt

@@ -2,10 +2,12 @@ package net.pokeranalytics.android.ui.adapter.components
 
 import android.view.View
 import android.view.ViewGroup
+import androidx.recyclerview.widget.DiffUtil
 import androidx.recyclerview.widget.RecyclerView
 import net.pokeranalytics.android.ui.view.BindableHolder
 import net.pokeranalytics.android.ui.view.RowRepresentable
 import net.pokeranalytics.android.ui.view.RowViewType
+import net.pokeranalytics.android.ui.view.RowRepresentableDiffCallback
 
 /**
  * An interface used to provide RowRepresentableAdapter content and value in the form of rows
@@ -62,7 +64,10 @@ interface RowRepresentableDelegate {
  * @param rowRepresentableDataSource the datasource providing rows
  * @param rowRepresentableDelegate the delegate, notified of UI actions
  */
-class RowRepresentableAdapter(var rowRepresentableDataSource: RowRepresentableDataSource, var rowRepresentableDelegate: RowRepresentableDelegate? = null) :
+class RowRepresentableAdapter(
+	var rowRepresentableDataSource: RowRepresentableDataSource,
+	var rowRepresentableDelegate: RowRepresentableDelegate? = null
+) :
 	RecyclerView.Adapter<RecyclerView.ViewHolder>() {
 
 	/**
@@ -119,4 +124,18 @@ class RowRepresentableAdapter(var rowRepresentableDataSource: RowRepresentableDa
 		notifyDataSetChanged()
 	}
 
+	/**
+	 * Update UI
+	 */
+	fun updateRows(newRows: ArrayList<RowRepresentable>) {
+		val diffResult = DiffUtil.calculateDiff(
+			RowRepresentableDiffCallback(
+				newRows,
+				rows
+			)
+		)
+		this.rows = newRows
+		diffResult.dispatchUpdatesTo(this)
+	}
+
 }

app/src/main/java/net/pokeranalytics/android/ui/fragment/SessionFragment.kt

@@ -5,7 +5,6 @@ import android.view.*
 import android.view.animation.OvershootInterpolator
 import android.widget.Toast
 import androidx.interpolator.view.animation.FastOutSlowInInterpolator
-import androidx.recyclerview.widget.LinearLayoutManager
 import io.realm.kotlin.where
 import kotlinx.android.synthetic.main.fragment_session.*
 import net.pokeranalytics.android.R
@@ -23,6 +22,7 @@ import net.pokeranalytics.android.ui.fragment.components.bottomsheet.BottomSheet
 import net.pokeranalytics.android.ui.fragment.components.bottomsheet.BottomSheetFragment
 import net.pokeranalytics.android.ui.view.RowRepresentable
 import net.pokeranalytics.android.ui.view.SessionRow
+import net.pokeranalytics.android.ui.view.SmoothScrollLinearLayoutManager
 import net.pokeranalytics.android.util.toast
 import timber.log.Timber
 import java.util.*
@@ -123,8 +123,7 @@ class SessionFragment : PokerAnalyticsFragment(), RowRepresentableDelegate, Bott
 		activity.supportActionBar?.setDisplayHomeAsUpEnabled(true)
 		setHasOptionsMenu(true)
 
-		val viewManager = LinearLayoutManager(requireContext())
+		val viewManager = SmoothScrollLinearLayoutManager(requireContext())
-
 		recyclerView.apply {
 			setHasFixedSize(true)
 			layoutManager = viewManager
@@ -186,7 +185,8 @@ class SessionFragment : PokerAnalyticsFragment(), RowRepresentableDelegate, Bott
 			}
 		}
 
-		sessionAdapter.refreshAllRows()
+		sessionAdapter.updateRows(currentSession.adapterRows())
+		recyclerView.smoothScrollToPosition(0)
 	}
 
 	/**

app/src/main/java/net/pokeranalytics/android/ui/view/RowRepresentableDiffCallback.kt

@@ -0,0 +1,32 @@
+package net.pokeranalytics.android.ui.view
+
+import androidx.annotation.Nullable
+import androidx.recyclerview.widget.DiffUtil
+import net.pokeranalytics.android.ui.view.RowRepresentable
+import timber.log.Timber
+
+class RowRepresentableDiffCallback(var newRows: List<RowRepresentable>, var oldRows: List<RowRepresentable>) :
+	DiffUtil.Callback() {
+
+	override fun getOldListSize(): Int {
+		return oldRows.size
+	}
+
+	override fun getNewListSize(): Int {
+		return newRows.size
+	}
+
+	override fun areItemsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
+		return oldRows[oldItemPosition] === newRows[newItemPosition]
+	}
+
+	override fun areContentsTheSame(oldItemPosition: Int, newItemPosition: Int): Boolean {
+		return oldRows[oldItemPosition] == newRows[newItemPosition]
+	}
+
+	@Nullable
+	override fun getChangePayload(oldItemPosition: Int, newItemPosition: Int): Any? {
+		//you can return particular field for changed item.
+		return super.getChangePayload(oldItemPosition, newItemPosition)
+	}
+}

app/src/main/java/net/pokeranalytics/android/ui/view/SmoothScrollLinearLayoutManager.kt

@@ -0,0 +1,46 @@
+package net.pokeranalytics.android.ui.view
+
+import android.content.Context
+import android.graphics.PointF
+import android.util.DisplayMetrics
+import androidx.recyclerview.widget.LinearLayoutManager
+import androidx.recyclerview.widget.LinearSmoothScroller
+import androidx.recyclerview.widget.RecyclerView
+
+/**
+ * SmoothScrollLinearLayoutManager
+ */
+class SmoothScrollLinearLayoutManager(context: Context) :
+	LinearLayoutManager(context, RecyclerView.VERTICAL, false) {
+
+	companion object {
+		private const val MILLISECONDS_PER_INCH = 100f
+	}
+
+	override fun smoothScrollToPosition(
+		recyclerView: RecyclerView, state: RecyclerView.State?,
+		position: Int
+	) {
+		val smoothScroller = TopSnappedSmoothScroller(recyclerView.context)
+		smoothScroller.targetPosition = position
+		startSmoothScroll(smoothScroller)
+	}
+
+	private inner class TopSnappedSmoothScroller(context: Context) : LinearSmoothScroller(context) {
+
+		override fun computeScrollVectorForPosition(targetPosition: Int): PointF? {
+			return this@SmoothScrollLinearLayoutManager
+				.computeScrollVectorForPosition(targetPosition)
+		}
+
+		override fun getVerticalSnapPreference(): Int {
+			return SNAP_TO_START
+		}
+
+		override fun calculateSpeedPerPixel(displayMetrics: DisplayMetrics): Float {
+			return MILLISECONDS_PER_INCH / displayMetrics.densityDpi
+		}
+	}
+
+
+}