perf: optimize stopwatch updates (#213)

* fix: bump stopwatch update interval to 100ms

The UI does not need to update 50 times a second.

* perf: optimize stopwatch updates

- Added a static id for live lap for cleaner logic
- Added `updateLiveLap` method to the stopwatch adapter. This is responsible for updating the live lap and maintaining its position in the list

* refactor: move Lap.kt to extensions package

app/src/main/kotlin/org/fossify/clock/adapters/StopwatchAdapter.kt

@@ -10,17 +10,22 @@ import org.fossify.clock.extensions.formatStopwatchTime
 import org.fossify.clock.helpers.SORT_BY_LAP
 import org.fossify.clock.helpers.SORT_BY_LAP_TIME
 import org.fossify.clock.helpers.SORT_BY_TOTAL_TIME
+import org.fossify.clock.extensions.isLive
 import org.fossify.clock.models.Lap
 import org.fossify.commons.adapters.MyRecyclerViewAdapter
 import org.fossify.commons.views.MyRecyclerView
 
 class StopwatchAdapter(
     activity: SimpleActivity,
-    var laps: ArrayList<Lap>,
+    private var laps: ArrayList<Lap>,
     recyclerView: MyRecyclerView,
     itemClick: (Any) -> Unit,
 ) : MyRecyclerViewAdapter(activity, recyclerView, itemClick) {
 
+    init {
+        recyclerView.itemAnimator = null
+    }
+
     override fun getActionMenuId() = 0
 
     override fun prepareActionMode(menu: Menu) {}
@@ -60,9 +65,26 @@ class StopwatchAdapter(
         finishActMode()
     }
 
+    fun updateLiveLap(totalTime: Long, lapTime: Long) {
+        val oldIndex = laps.indexOfFirst { it.isLive() }
+        if (oldIndex == -1) return
+        laps[oldIndex].lapTime = lapTime
+        laps[oldIndex].totalTime = totalTime
+        laps.sort()
+
+        // the live lap might have changed position
+        val newIndex = laps.indexOfFirst { it.isLive() }
+        if (oldIndex == newIndex) {
+            notifyItemChanged(newIndex)
+        } else {
+            notifyItemMoved(oldIndex, newIndex)
+            notifyItemChanged(newIndex)
+        }
+    }
+
     private fun setupView(view: View, lap: Lap) {
         ItemLapBinding.bind(view).apply {
-            lapOrder.text = lap.id.toString()
+            lapOrder.text = if (lap.isLive()) laps.size.toString() else lap.id.toString()
             lapOrder.setTextColor(textColor)
             lapOrder.setOnClickListener {
                 itemClick(SORT_BY_LAP)

app/src/main/kotlin/org/fossify/clock/extensions/Lap.kt

@@ -0,0 +1,6 @@
+package org.fossify.clock.extensions
+
+import org.fossify.clock.helpers.STOPWATCH_LIVE_LAP_ID
+import org.fossify.clock.models.Lap
+
+fun Lap.isLive() = id == STOPWATCH_LIVE_LAP_ID

app/src/main/kotlin/org/fossify/clock/fragments/StopwatchFragment.kt

@@ -17,6 +17,7 @@ import org.fossify.clock.extensions.formatStopwatchTime
 import org.fossify.clock.helpers.SORT_BY_LAP
 import org.fossify.clock.helpers.SORT_BY_LAP_TIME
 import org.fossify.clock.helpers.SORT_BY_TOTAL_TIME
+import org.fossify.clock.helpers.STOPWATCH_LIVE_LAP_ID
 import org.fossify.clock.helpers.Stopwatch
 import org.fossify.clock.models.Lap
 import org.fossify.commons.dialogs.PermissionRequiredDialog
@@ -38,7 +39,7 @@ import org.fossify.commons.helpers.SORT_DESCENDING
 
 class StopwatchFragment : Fragment() {
 
-    lateinit var stopwatchAdapter: StopwatchAdapter
+    private var stopwatchAdapter: StopwatchAdapter? = null
     private lateinit var binding: FragmentStopwatchBinding
 
     private var latestLapTime: Long = 0L
@@ -129,6 +130,12 @@ class StopwatchFragment : Fragment() {
             )
             stopwatchReset.applyColorFilter(requireContext().getProperTextColor())
         }
+
+        stopwatchAdapter?.apply {
+            updatePrimaryColor()
+            updateBackgroundColor(requireContext().getProperBackgroundColor())
+            updateTextColor(requireContext().getProperTextColor())
+        }
     }
 
     private fun updateIcons(state: Stopwatch.State) {
@@ -233,37 +240,28 @@ class StopwatchFragment : Fragment() {
         val allLaps = ArrayList(Stopwatch.laps)
         if (Stopwatch.laps.isNotEmpty() && Stopwatch.state != Stopwatch.State.STOPPED) {
             allLaps += Lap(
-                id = Stopwatch.laps.size + 1,
+                id = STOPWATCH_LIVE_LAP_ID,
                 lapTime = latestLapTime,
                 totalTime = latestTotalTime
             )
         }
 
         allLaps.sort()
-        stopwatchAdapter.apply {
-            updatePrimaryColor()
-            updateBackgroundColor(requireContext().getProperBackgroundColor())
-            updateTextColor(requireContext().getProperTextColor())
-            updateItems(allLaps)
-        }
+        stopwatchAdapter?.updateItems(allLaps)
     }
 
     private val updateListener = object : Stopwatch.UpdateListener {
         override fun onUpdate(totalTime: Long, lapTime: Long, useLongerMSFormat: Boolean) {
-            activity?.runOnUiThread {
-                binding.stopwatchTime.text = totalTime.formatStopwatchTime(useLongerMSFormat)
-                latestLapTime = lapTime
-                latestTotalTime = totalTime
-                updateLaps()
-            }
+            binding.stopwatchTime.text = totalTime.formatStopwatchTime(useLongerMSFormat)
+            latestLapTime = lapTime
+            latestTotalTime = totalTime
+            stopwatchAdapter?.updateLiveLap(totalTime, lapTime)
         }
 
         override fun onStateChanged(state: Stopwatch.State) {
-            activity?.runOnUiThread {
-                updateIcons(state)
-                binding.stopwatchLap.beVisibleIf(state == Stopwatch.State.RUNNING)
-                binding.stopwatchReset.beVisibleIf(state != Stopwatch.State.STOPPED)
-            }
+            updateIcons(state)
+            binding.stopwatchLap.beVisibleIf(state == Stopwatch.State.RUNNING)
+            binding.stopwatchReset.beVisibleIf(state != Stopwatch.State.STOPPED)
         }
     }
 }

app/src/main/kotlin/org/fossify/clock/helpers/Constants.kt

@@ -83,6 +83,8 @@ const val SORT_BY_LAP = 1
 const val SORT_BY_LAP_TIME = 2
 const val SORT_BY_TOTAL_TIME = 4
 
+const val STOPWATCH_LIVE_LAP_ID = Int.MAX_VALUE
+
 // alarm and timer sorting
 const val SORT_BY_CREATION_ORDER = 0
 const val SORT_BY_ALARM_TIME = 1

app/src/main/kotlin/org/fossify/clock/helpers/Stopwatch.kt

@@ -11,7 +11,7 @@ import kotlinx.coroutines.launch
 import org.fossify.clock.models.Lap
 import java.util.concurrent.CopyOnWriteArraySet
 
-private const val UPDATE_INTERVAL_MS = 20L
+private const val UPDATE_INTERVAL_MS = 100L
 
 object Stopwatch {
     private var startTime = 0L