mounted property
      
      Future<void> 
      get
      mounted
      
    
    
A future that will complete once the component is mounted on its parent.
If the component is already mounted (see isMounted), this returns an already completed future.
Implementation
Future<void> get mounted {
  return isMounted
      ? Future.value()
      : (_mountCompleter ??= Completer<void>()).future;
}