Flutter setState callBack fn方法区别

区别

 setState(() {
  _counter++;
  });

  _counter++;
 setState(() {
  });

看源码：

void setState(VoidCallback fn) {
    assert(fn != null);
    assert(() {
      if (_debugLifecycleState == _StateLifecycle.defunct) {
      //throw
      }
      if (_debugLifecycleState == _StateLifecycle.created && !mounted) {
      //throw
      }
      return true;
    }());
    final Object? result = fn() as dynamic;
    assert(() {
      if (result is Future) { 
        //throw
      }
      return true;
    }());
    _element!.markNeedsBuild();
  }

从上可以看出来，两种写法，本质上没有什么区别。
都是执行 _counter++; 语句之后，
调用 _element!.markNeedsBuild(); 刷新界面