IOSPlatformView: document that the [FlutterPlatformView view] should not return a new instance every time its called #56736
Description
The view API is declared here:
https://github.com/flutter/engine/blob/master/shell/platform/darwin/ios/framework/Headers/FlutterPlatformViews.h#L22
After we implemented the unobstructed platform view. We need the embedded view to be cached. As a result, the platform view implementer must not create a new instance of the platform view every frame.
It was never a good practice anyway as it reduces performance.
One example of good implementation of platform view would be:
class UIRectView: NSObject, FlutterPlatformView {
let embedded_view: UIView
init(_ frame: CGRect) {
embedded_view = UIView(frame: frame)
embedded_view.backgroundColor = UIColor.cyan
}
func view() -> UIView {
return embedded_view
}
}A bad example would be:
class UIRectView: NSObject, FlutterPlatformView {
func view() -> UIView {
let embedded_view = UIView(frame: frame)
embedded_view.backgroundColor = UIColor.cyan
return embedded_view;
}
}We should document the same in the public API.