Flutter 区分小部件的多个实例

Question

I'm writing an app where I'm using multiple instance of a custom widget, and i want to call a method of a specific instance.

Sample of the code:

Widget build(BuildContext context) {
        return Scaffold(
            drawer: new DrawerOnly(storage: CounterStorage()),
            appBar: AppBar(),
            body: Stack(
                children: <Widget>[
                    new Center(
                        child: new Object3D(

                        ),
                    ),
                    new Positioned(
                        top: 20,
                        left: 0,
                        child: new Object3D(

                        ),
                    ),
                    new Positioned(
                        top: 20,
                        left: 100,
                        child: new Object3D(

                        ),
                    ),
                    new Positioned(
                        top: 120,
                        left: 0,
                        child: new Object3D(

                        ),
                    ),
                ],
            )
        );
    }

    mymethod() {
        //call first Object3D's method from here
    }
}

how do i call the first Object3D's method from their parent?

Answer 1

You store your children in a list like this:

final object3Ds = List<Object3D>.generate(4, (_) => Object3D());

Now, you store that reference in your parent and then you can pass the elements of that list in your build method:

...
Stack(
  children: <Widget>[
    Positioned(
      child: object3Ds[0],
      ...

Finally, you can now access your objects using the list you created:

object3Ds[0].callMethod();