addPlatformView method

void addPlatformView (int viewId, { Offset offset: Offset.zero, double width: 0.0, double height: 0.0 })

Adds a platform view (e.g an iOS UIView) to the scene.

Only supported on iOS, this is currently a no-op on other platforms.

On iOS this layer splits the current output surface into two surfaces, one for the scene nodes preceding the platform view, and one for the scene nodes following the platform view.

Performance impact

Adding an additional surface doubles the amount of graphics memory directly used by Flutter for output buffers. Quartz might allocated extra buffers for compositing the Flutter surfaces and the platform view.

With a platform view in the scene, Quartz has to composite the two Flutter surfaces and the embedded UIView. In addition to that, on iOS versions greater than 9, the Flutter frames are synchronized with the UIView frames adding additional performance overhead.

Implementation 

void addPlatformView(int viewId, { Offset offset: Offset.zero, double width: 0.0, double height: 0.0}) {
  assert(offset != null, 'Offset argument was null');
  _addPlatformView(offset.dx, offset.dy, width, height, viewId);
}