Flutter macos change background on button click

Question

at the moment im experimenting with the flutter macos application. Basically I want to create a button in my macos app which sets a background image on my macbook. Creating the button ofcourse is not the problem. I dont know how to "call" my macs background to change on button click. I also dont have any idea on how and furthermore what to research. This is my code...

Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Column(
        mainAxisAlignment: MainAxisAlignment.spaceEvenly,
        children: [
          ElevatedButton(
            child: const Text('Set Background Image to my Mac'),
            onPressed: _setBackgroundImage(),
          ),
          Text(currentBackgroundName),
        ],
      ),
      ),
    );
  }

Does someone has an idea?