fix: restore bitmap recycling on children changes (#1864)

PR fixing the regression introduced in #1844. In that PR we set mRemovedFromReactViewHierarchy after one of SvgView's children has been removed, resulting in not being able to update it after one of the components in its hierarchy has been removed. In this PR the behavior has been changed, now we subscribe to startViewTransition which should be called only by react-native-screens when the screen starts its removal animation. It should still work for old issues as well as the new ones.

android/src/main/java/com/horcrux/svg/RenderableViewManager.java

@@ -530,10 +530,6 @@ public void onChildViewAdded(View view, View view1) {
           @Override
           public void onChildViewRemoved(View view, View view1) {
             if (view instanceof VirtualView) {
-              SvgView svgView = ((VirtualView) view).getSvgView();
-              if (svgView != null) {
-                svgView.setRemovedFromReactViewHierarchy();
-              }
               invalidateSvgView((V) view);
             }
           }

android/src/main/java/com/horcrux/svg/SvgView.java

@@ -59,7 +59,7 @@ public String toString() {
   }
 
   private @Nullable Bitmap mBitmap;
-  private boolean mRemovedFromReactViewHierarchy;
+  private boolean mRemovalTransitionStarted;
 
   public SvgView(ReactContext reactContext) {
     super(reactContext);
@@ -74,10 +74,6 @@ public void setId(int id) {
     SvgViewManager.setSvgView(id, this);
   }
 
-  public void setRemovedFromReactViewHierarchy() {
-    mRemovedFromReactViewHierarchy = true;
-  }
-
   @Override
   public void invalidate() {
     super.invalidate();
@@ -90,7 +86,7 @@ public void invalidate() {
       ((VirtualView) parent).getSvgView().invalidate();
       return;
     }
-    if (!mRemovedFromReactViewHierarchy) {
+    if (!mRemovalTransitionStarted) {
       // when view is removed from the view hierarchy, we want to recycle the mBitmap when
       // the view is detached from window, in order to preserve it for during animation, see
       // https://github.com/react-native-svg/react-native-svg/pull/1542
@@ -101,6 +97,11 @@ public void invalidate() {
     }
   }
 
+  @Override
+  public void startViewTransition(View view) {
+    mRemovalTransitionStarted = true;
+  }
+
   @Override
   protected void onDetachedFromWindow() {
     super.onDetachedFromWindow();