flutter如何使用alertDialog？

Question

I'm making sign in system in flutter.

I want to use alertDialog for sign in failed.

if-else is included in onpressed:

else {
                      AlertDialog(
                        title: Column(
                          children: <Widget>[
                            new Text("Log in failed"),
                          ],
                        ),
                        //
                        content: Column(
                          mainAxisSize: MainAxisSize.min,
                          crossAxisAlignment: CrossAxisAlignment.start,
                          children: <Widget>[
                            Text(
                              "ID or Password doesn't exist",
                            ),
                          ],
                        ),
                        actions: <Widget>[
                          new FlatButton(
                            child: new Text("OK"),
                            onPressed: () {
                              Navigator.pop(context);
                            },
                          ),
                        ],
                      );

Writing return doesn't work and deleting return doesn't show anything.

How to fix this?

Answer 1

You need to call showDialog and pass the AlertDialog you created.

The demo I created on DartPad .

await showDialog(
  context: context,
  builder: (context) => AlertDialog(
    title: Column(
      children: <Widget>[
        new Text("Log in failed"),
      ],
    ),
    //
    content: Column(
      mainAxisSize: MainAxisSize.min,
      crossAxisAlignment: CrossAxisAlignment.start,
      children: <Widget>[
        Text(
          "ID or Password doesn't exist",
        ),
      ],
    ),
    actions: <Widget>[
      new FlatButton(
        child: new Text("OK"),
        onPressed: () {
          Navigator.pop(context);
        },
      ),
    ],
  ),
);

Note: Use TextButton instead of FlatButton because FlatButton is deprecated .