导航后打开Flutter对话框

问题描述：

我致电Navigator pushReplacement以在我的flutter应用程序中显示一个新视图，并想立即弹出一个简单对话框，向用户介绍该页面. (我希望用户能够在后台看到新视图)

I call Navigator pushReplacement to show a new view within my flutter app and want to immediately pop up a simple dialog to introduce the page to the user. (I want the user to be able to see the new view in the background)

如果我在窗口小部件的build方法内调用showDialog，然后随后从build方法返回窗口小部件(支架)，则会出现错误，表明flutter已经在绘制窗口小部件.我希望我需要侦听构建完成事件，然后调用showDialog.

If I call showDialog within the build method of a widget, and then subsequently return a widget (scaffold) from the build method I get errors stating that flutter is already drawing a widget. I expect I need to listen on a build complete event and then call showDialog.

有关如何做到这一点的指导.

Guidance on how to do that much appreciated.

答

您可以从"initState()"内部调用对话框，在绘制第一帧后就可以保留对话框的外观.

You can call the dialog from inside 'initState()' dalaying its appearance after the first frame has been drawn.

  @override
  void initState() {
    super.initState();
    WidgetsBinding.instance.addPostFrameCallback((_) async {
      await showDialog<String>(
        context: context,
        builder: (BuildContext context) => new AlertDialog(
              title: new Text("title"),
              content: new Text("Message"),
              actions: <Widget>[
                new FlatButton(
                  child: new Text("OK"),
                  onPressed: () {
                    Navigator.of(context).pop();
                  },
                ),
              ],
            ),
      );
    });
  }

导航后打开Flutter对话框

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