improve animation performance

app/src/main/java/com/johan/evmap/fragment/MapFragment.kt

@@ -302,10 +302,7 @@ class MapFragment : Fragment(), OnMapReadyCallback, MapsActivity.FragmentCallbac
                 MarkerOptions()
                     .position(LatLng(charger.coordinates.lat, charger.coordinates.lng))
                     .icon(
-                        chargerIconGenerator.getBitmapDescriptor(
-                            R.drawable.ic_map_marker_charging,
-                            tint
-                        )
+                        chargerIconGenerator.getBitmapDescriptor(tint)
                     )
             )
             animateMarkerAppear(marker, tint, chargerIconGenerator)

app/src/main/java/com/johan/evmap/ui/IconGenerators.kt

@@ -5,9 +5,9 @@ import android.graphics.Bitmap
 import android.graphics.Canvas
 import android.graphics.PorterDuff
 import android.graphics.drawable.Drawable
+import android.util.LruCache
 import android.view.ViewGroup
 import androidx.annotation.ColorRes
-import androidx.annotation.DrawableRes
 import androidx.core.content.ContextCompat
 import androidx.core.graphics.drawable.DrawableCompat
 import com.google.android.gms.maps.model.BitmapDescriptor
@@ -40,29 +40,56 @@ class ClusterIconGenerator(context: Context) : IconGenerator(context) {
 
 
 class ChargerIconGenerator(val context: Context) {
-    data class BitmapData(val id: Int, val tint: Int, val scale: Int, val alpha: Int)
+    data class BitmapData(val tint: Int, val scale: Int, val alpha: Int)
 
-    val cache = hashMapOf<BitmapData, Bitmap>()
+    val cacheSize = 4 * 1024 * 1024; // 4MiB
+    val cache = object : LruCache<BitmapData, Bitmap>(cacheSize) {
+        override fun sizeOf(key: BitmapData, value: Bitmap): Int {
+            return value.byteCount
+        }
+    }
     val oversize = 1.5f
+    val icon = R.drawable.ic_map_marker_charging
+
+    init {
+        preloadCache()
+    }
+
+    fun preloadCache() {
+        // pre-generates images for scale from 0 to 255 for all possible tint colors
+        val tints = listOf(
+            R.color.charger_100kw,
+            R.color.charger_43kw,
+            R.color.charger_20kw,
+            R.color.charger_11kw,
+            R.color.charger_low
+        )
+        for (tint in tints) {
+            for (scale in 0..20) {
+                val data = BitmapData(tint, scale, 255)
+                cache.put(data, generateBitmap(data))
+            }
+        }
+    }
 
     fun getBitmapDescriptor(
-        @DrawableRes id: Int,
         @ColorRes tint: Int,
-        scale: Int = 255,
+        scale: Int = 20,
         alpha: Int = 255
     ): BitmapDescriptor? {
-        val data = BitmapData(id, tint, scale, alpha)
-        if (cache.containsKey(data)) {
-            return BitmapDescriptorFactory.fromBitmap(cache[data])
+        val data = BitmapData(tint, scale, alpha)
+        val cachedImg = cache[data]
+        return if (cachedImg != null) {
+            BitmapDescriptorFactory.fromBitmap(cachedImg)
         } else {
             val bitmap = generateBitmap(data)
-            cache[data] = bitmap
-            return BitmapDescriptorFactory.fromBitmap(bitmap)
+            cache.put(data, bitmap)
+            BitmapDescriptorFactory.fromBitmap(bitmap)
         }
     }
 
     private fun generateBitmap(data: BitmapData): Bitmap {
-        val vd: Drawable = context.getDrawable(data.id)!!
+        val vd: Drawable = context.getDrawable(icon)!!
 
         DrawableCompat.setTint(vd, ContextCompat.getColor(context, data.tint));
         DrawableCompat.setTintMode(vd, PorterDuff.Mode.MULTIPLY);
@@ -82,7 +109,7 @@ class ChargerIconGenerator(val context: Context) {
         )
         val canvas = Canvas(bm)
 
-        val scale = data.scale / 255f
+        val scale = data.scale / 20f
         canvas.scale(
             scale,
             scale,

app/src/main/java/com/johan/evmap/ui/MarkerUtils.kt

@@ -21,7 +21,7 @@ fun animateMarkerAppear(
     tint: Int,
     gen: ChargerIconGenerator
 ) {
-    ValueAnimator.ofInt(0, 255).apply {
+    ValueAnimator.ofInt(0, 20).apply {
         duration = 250
         interpolator = LinearOutSlowInInterpolator()
         addUpdateListener { animationState ->
@@ -31,11 +31,7 @@ fun animateMarkerAppear(
             }
             val scale = animationState.animatedValue as Int
             marker.setIcon(
-                gen.getBitmapDescriptor(
-                    R.drawable.ic_map_marker_charging,
-                    tint,
-                    scale = scale
-                )
+                gen.getBitmapDescriptor(tint, scale = scale)
             )
         }
     }.start()
@@ -46,7 +42,7 @@ fun animateMarkerDisappear(
     tint: Int,
     gen: ChargerIconGenerator
 ) {
-    ValueAnimator.ofInt(255, 0).apply {
+    ValueAnimator.ofInt(20, 0).apply {
         duration = 200
         interpolator = FastOutLinearInInterpolator()
         addUpdateListener { animationState ->
@@ -56,11 +52,7 @@ fun animateMarkerDisappear(
             }
             val scale = animationState.animatedValue as Int
             marker.setIcon(
-                gen.getBitmapDescriptor(
-                    R.drawable.ic_map_marker_charging,
-                    tint,
-                    scale = scale
-                )
+                gen.getBitmapDescriptor(tint, scale = scale)
             )
         }
         addListener(onEnd = {