show dialog box in flutter code example

Example 1: show dialog close flutter

BuildContext dialogContext; // <<----
  showDialog(
    context: context, // <<----
    barrierDismissible: false,
    builder: (BuildContext context) {
      dialogContext = context;
      return Dialog(
        child: new Row(
          mainAxisSize: MainAxisSize.min,
          children: [
            new CircularProgressIndicator(),
            new Text("Loading"),
          ],
        ),
      );
    },
  );

  await _longOperation();
  Navigator.pop(dialogContext); // <<----

Example 2: flutter alertdialog

create a methos _showDialog
then call it in your state

// user defined function
  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();
              },
            ),
          ],
        );
      },
    );
  }

Example 3: alertdialog flutter

showAlertDialog(BuildContext context) {

  // set up the button
  Widget okButton = FlatButton(
    child: Text("OK"),
    onPressed: () { },
  );

  // set up the AlertDialog
  AlertDialog alert = AlertDialog(
    title: Text("My title"),
    content: Text("This is my message."),
    actions: [
      okButton,
    ],
  );

  // show the dialog
  showDialog(
    context: context,
    builder: (BuildContext context) {
      return alert;
    },
  );
}

Example 4: show dialog box on pressed flutter

@override
Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(title: Text("Testing")),
    body: Center(
      child: RaisedButton(
        child: Text("Show dialog"),
        onPressed: () {
          showDialog(
            context: context,
            builder: (context) {
              return Dialog(
                shape: RoundedRectangleBorder(borderRadius: BorderRadius.circular(40)),
                elevation: 16,
                child: Container(
                  height: 400.0,
                  width: 360.0,
                  child: ListView(
                    children: <Widget>[
                      SizedBox(height: 20),
                      Center(
                        child: Text(
                          "Leaderboard",
                          style: TextStyle(fontSize: 24, color: Colors.blue, fontWeight: FontWeight.bold),
                        ),
                      ),
                      SizedBox(height: 20),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 1", score: 1000),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 2", score: 2000),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 3", score: 3000),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 4", score: 4000),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 5", score: 5000),
                      _buildName(imageAsset: 'assets/chocolate.jpg', name: "Name 6", score: 6000),
                    ],
                  ),
                ),
              );
            },
          );
        },
      ),
    ),
  );
}

Widget _buildName({String imageAsset, String name, double score}) {
  return Padding(
    padding: const EdgeInsets.symmetric(horizontal: 20.0),
    child: Column(
      children: <Widget>[
        SizedBox(height: 12),
        Container(height: 2, color: Colors.redAccent),
        SizedBox(height: 12),
        Row(
          children: <Widget>[
            CircleAvatar(
              backgroundImage: AssetImage(imageAsset),
              radius: 30,
            ),
            SizedBox(width: 12),
            Text(name),
            Spacer(),
            Container(
              padding: EdgeInsets.symmetric(vertical: 8, horizontal: 20),
              child: Text("${score}"),
              decoration: BoxDecoration(
                color: Colors.yellow[900],
                borderRadius: BorderRadius.circular(20),
              ),
            ),
          ],
        ),
      ],
    ),
  );
}