如何检查窗口小部件是否已安装在颤动中

Question

所以在我的应用程序中，我想在挂载小部件后立即发出Ajax请求，而不是在initState()中。类似于react

中的ComponentWillMount()

Answer 1

我认为目前不可能。

这里是mounted属性：https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/widgets/framework.dart#L974

bool get mounted => _element != null;

这里是设置_element的时间：https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/widgets/framework.dart#L3816

_state._element = this

而且我在此代码周围看不到任何钩子会通知我们。

为什么仍不使用initState？这可能是您想要的。这是mounted属性上方的注释：https://github.com/flutter/flutter/blob/master/packages/flutter/lib/src/widgets/framework.dart#L967

  /// After creating a [State] object and before calling [initState], the
  /// framework "mounts" the [State] object by associating it with a
  /// [BuildContext]. The [State] object remains mounted until the framework

Answer 2

如果小部件没有mounted，则返回。在setState方法之前执行>

if (!mounted) return;
setState(() {});
或

if (mounted) {
   //Do something
};
setState(() {});