ModalProgressHUD(
  @required inAsyncCall: bool,
  @required child: Widget,
  opacity: double,
  color: Color,
  progressIndicator: CircularProgressIndicator,
  offset: double
  dismissible: bool,
);

Example

Here is an example app that demonstrates the usage.

1. On initial load, _saving is false which causes your child widget to display
2. When the form is submitted, _saving is set to true, which will display the modal
3. Once the async call is complete, _saving is set back to false, hiding the modal

class SettingsPage extends StatefulWidget {
  @override
  _SettingsPageState createState() => new _SettingsPageState();
}

class _SettingsPageState extends State<SettingsPage> {
  bool _saving = false;

  void _submit() {

    setState(() {
      _saving = true;
    });

    //Simulate a service call
    print('submitting to backend...');
    new Future.delayed(new Duration(seconds: 4), () {
      setState(() {
        _saving = false;
      });
    });
  }

  Widget _buildWidget() {
    return new Form(
      child: new Column(
        children: [
          new SwitchListTile(
            title: const Text('Bedroom'),
            value: _bedroom,
            onChanged: (bool value) {
              setState(() {
                _bedroom = value;
              });
            },
            secondary: const Icon(Icons.hotel),
          ),
          new RaisedButton(
            onPressed: _submit,
            child: new Text('Save'),
          ),
        ],
      ),
    );
  }

  @override
  Widget build(BuildContext context) {
    return new Scaffold(
      appBar: new AppBar(
        title: new Text('Flutter Progress Indicator Demo'),
        backgroundColor: Colors.blue,
      ),
      body: ModalProgressHUD(child: _buildWidget(), inAsyncCall: _saving),
    );
  }
}