Show alert dialog on app main screen load automatically

[Rajeev Mishra]

0down votefavorite

I want to show alert dialog based on a condition. Not based on user interaction such as button press event.

If a flag is set in app state data alert dialog is shown otherwise its not.

Below is the sample alert dialog which I want to show

  void _showDialog() {
    // flutter defined function
    showDialog(
      context: context,
      builder: (BuildContext context) {
        // return object of type Dialog
        return AlertDialog(
          title: new Text("Alert Dialog title"),
          content: new Text("Alert Dialog body"),
          actions: <Widget>[
            // usually buttons at the bottom of the dialog
            new FlatButton(
              child: new Text("Close"),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          ],
        );
      },
    );
  }

I tried to call that method inside main screen widget's build method but it gives me error -

 The context used to push or pop routes from the Navigator must be that of a widget that is a descendant of a Navigator widget.
E/flutter ( 3667): #0      Navigator.of.<anonymous closure> (package:flutter/src/widgets/navigator.dart:1179:9)
E/flutter ( 3667): #1      Navigator.of (package:flutter/src/widgets/navigator.dart:1186:6)
E/flutter ( 3667): #2      showDialog (package:flutter/src/material/dialog.dart:642:20)

Problem is I don't know from where I should call that _showDialog method?

I have asked a question as well on stack overflow

https://stackoverflow.com/questions/52164369/show-alert-dialog-on-app-main-screen-load-automatically

[Matt Carroll]

Hi Rajeev,

Do you definitely have a Navigator higher up in your UI hierarchy?  It looks like you're calling the showDialog() method from within a State Object, is that right?  If so, can you share the Widget hierarchy above that State?

The specific error you're receiving is because Flutter is looking for a Navigator to use for the dialog but it can't find one.

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