tracksViewChanges for android [https://github.com/react-native-community/react-native-maps/pull/2477](https://github.com/react-native-community/react-native-maps/pull/2477)

Author: Stalder

lib/android/src/main/java/com/airbnb/android/react/maps/AirMapMarker.java

@@ -73,6 +73,9 @@ public class AirMapMarker extends AirMapFeature {
   private float calloutAnchorY;
   private boolean calloutAnchorIsSet;
 
+  private boolean tracksViewChanges = true;
+  private boolean tracksViewChangesActive = false;
+
   private boolean hasCustomMarkerView = false;
 
   private final DraweeHolder<?> logoHolder;
@@ -240,6 +243,32 @@ public void setCalloutAnchor(double x, double y) {
     update();
   }
 
+    public void setTracksViewChanges(boolean tracksViewChanges) {
+    this.tracksViewChanges = tracksViewChanges;
+    updateTracksViewChanges();
+  }
+
+  private void updateTracksViewChanges() {
+    boolean shouldTrack = tracksViewChanges && hasCustomMarkerView && marker != null;
+    if (shouldTrack == tracksViewChangesActive) return;
+    tracksViewChangesActive = shouldTrack;
+
+    if (shouldTrack) {
+      ViewChangesTracker.getInstance().addMarker(this);
+    } else {
+      ViewChangesTracker.getInstance().removeMarker(this);
+    }
+  }
+
+  public boolean updateCustomMarkerIcon() {
+    if (!tracksViewChangesActive)
+      return false;
+
+    marker.setIcon(getIcon());
+
+    return true;
+  }
+
   public LatLng interpolate(float fraction, LatLng a, LatLng b) {
     double lat = (b.latitude - a.latitude) * fraction + a.latitude;
     double lng = (b.longitude - a.longitude) * fraction + a.longitude;
@@ -313,6 +342,7 @@ public void addView(View child, int index) {
     // if children are added, it means we are rendering a custom marker
     if (!(child instanceof AirMapCallout)) {
       hasCustomMarkerView = true;
+      updateTracksViewChanges();
     }
     update();
   }
@@ -325,12 +355,14 @@ public Object getFeature() {
   @Override
   public void addToMap(GoogleMap map) {
     marker = map.addMarker(getMarkerOptions());
+    updateTracksViewChanges();
   }
 
   @Override
   public void removeFromMap(GoogleMap map) {
     marker.remove();
     marker = null;
+    updateTracksViewChanges();
   }
 
   private BitmapDescriptor getIcon() {

lib/android/src/main/java/com/airbnb/android/react/maps/ViewChangesTracker.java

@@ -0,0 +1,75 @@
+package com.airbnb.android.react.maps;
+
+import android.os.Handler;
+import android.os.Looper;
+
+import java.util.LinkedList;
+
+public class ViewChangesTracker {
+
+  private static ViewChangesTracker instance;
+  private Handler handler;
+  private LinkedList<AirMapMarker> markers = new LinkedList<>();
+  private boolean hasScheduledFrame = false;
+  private Runnable updateRunnable;
+  private final long fps = 40;
+
+  private ViewChangesTracker() {
+    handler = new Handler(Looper.myLooper());
+    updateRunnable = new Runnable() {
+      @Override
+      public void run() {
+        hasScheduledFrame = false;
+        update();
+
+        if (markers.size() > 0) {
+          handler.postDelayed(updateRunnable, fps);
+        }
+      }
+    };
+  }
+
+  static ViewChangesTracker getInstance() {
+    if (instance == null) {
+      synchronized (ViewChangesTracker.class) {
+        instance = new ViewChangesTracker();
+      }
+    }
+
+    return instance;
+  }
+
+  public void addMarker(AirMapMarker marker) {
+    markers.add(marker);
+
+    if (!hasScheduledFrame) {
+      hasScheduledFrame = true;
+      handler.postDelayed(updateRunnable, fps);
+    }
+  }
+
+  public void removeMarker(AirMapMarker marker) {
+    markers.remove(marker);
+  }
+
+  public boolean containsMarker(AirMapMarker marker) {
+    return markers.contains(marker);
+  }
+
+  private LinkedList<AirMapMarker> markersToRemove = new LinkedList<>();
+
+  public void update() {
+    for (AirMapMarker marker : markers) {
+      if (!marker.updateCustomMarkerIcon()) {
+        markersToRemove.add(marker);
+      }
+    }
+
+    // Remove markers that are not active anymore
+    if (markersToRemove.size() > 0) {
+      markers.removeAll(markersToRemove);
+      markersToRemove.clear();;
+    }
+  }
+
+}