如何使属性只在Dart中的抽象类中可读？

abstract class AbstractClass {
  final int readOnlyProperty;

  AbstractClass(this.readOnlyProperty);

  void printProperty() {
    print(readOnlyProperty);
  }
}

class ConcreteClass extends AbstractClass {
  ConcreteClass(int readOnlyProperty) : super(readOnlyProperty);
}

void main() {
  var instance = ConcreteClass(10);
  instance.printProperty(); // 输出：10
  // instance.readOnlyProperty = 20; // 错误，无法修改只读属性
}