Complete Example for Normal Progress Dialog

import 'package:flutter/material.dart';
import 'package:progress_dialog/progress_dialog.dart';

ProgressDialog pr;

void main() {
  runApp(MaterialApp(
    home: MyApp(),
  ));
}

class MyApp extends StatelessWidget {
  double percentage = 0.0;

  @override
  Widget build(BuildContext context) {

    pr = new ProgressDialog(context,type: ProgressDialogType.Normal);

    pr.style(message: 'Showing some progress...');
    
    //Optional
    pr.style(
          message: 'Please wait...',
          borderRadius: 10.0,
          backgroundColor: Colors.white,
          progressWidget: CircularProgressIndicator(),
          elevation: 10.0,
          insetAnimCurve: Curves.easeInOut,
          progressTextStyle: TextStyle(
              color: Colors.black, fontSize: 13.0, fontWeight: FontWeight.w400),
          messageTextStyle: TextStyle(
              color: Colors.black, fontSize: 19.0, fontWeight: FontWeight.w600),
        );    

    return Scaffold(
      body: Center(
        child: RaisedButton(
            child: Text(
              'Show Dialog',
              style: TextStyle(color: Colors.white),
            ),
            color: Colors.blue,
            onPressed: () {
              pr.show();
              
              Future.delayed(Duration(seconds: 10)).then((onValue){
                print("PR status  ${pr.isShowing()}" );
                if(pr.isShowing())
                  pr.hide().then((isHidden) {
                    print(isHidden);
                  });
                print("PR status  ${pr.isShowing()}" );
              });

            }),
      ),
    );
  }
}

Complete Example for Download Progress Dialog

import 'package:flutter/material.dart';
import 'package:progress_dialog/progress_dialog.dart';

ProgressDialog pr;

void main() {
  runApp(MaterialApp(
    home: MyApp(),
  ));
}

class MyApp extends StatelessWidget {
  double percentage = 0.0;

  @override
  Widget build(BuildContext context) {

    pr = new ProgressDialog(context, type: ProgressDialogType.Download);
    pr.style(message: 'Downloading file...');
    
    //Optional
    pr.style(
          message: 'Downloading file...',
          borderRadius: 10.0,
          backgroundColor: Colors.white,
          progressWidget: CircularProgressIndicator(),
          elevation: 10.0,
          insetAnimCurve: Curves.easeInOut,
          progress: 0.0,
          maxProgress: 100.0,
          progressTextStyle: TextStyle(
              color: Colors.black, fontSize: 13.0, fontWeight: FontWeight.w400),
          messageTextStyle: TextStyle(
              color: Colors.black, fontSize: 19.0, fontWeight: FontWeight.w600),
        );
    
    return Scaffold(
      body: Center(
        child: RaisedButton(
            child: Text(
              'Show Dialog',
              style: TextStyle(color: Colors.white),
            ),
            color: Colors.blue,
            onPressed: () {
              pr.show();

              Future.delayed(Duration(seconds: 2)).then((onvalue) {
                percentage = percentage + 30.0;
                print(percentage);
                
                pr.update(
                  progress: percentage,
                  message: "Please wait...",
                  progressWidget: Container(
                      padding: EdgeInsets.all(8.0), child: CircularProgressIndicator()),
                  maxProgress: 100.0,
                  progressTextStyle: TextStyle(
                      color: Colors.black, fontSize: 13.0, fontWeight: FontWeight.w400),
                  messageTextStyle: TextStyle(
                      color: Colors.black, fontSize: 19.0, fontWeight: FontWeight.w600),
                );
                
                Future.delayed(Duration(seconds: 2)).then((value) {
                  percentage = percentage + 30.0;
                  pr.update(
                      progress: percentage, message: "Few more seconds...");
                  print(percentage);
                  Future.delayed(Duration(seconds: 2)).then((value) {
                    percentage = percentage + 30.0;
                    pr.update(progress: percentage, message: "Almost done...");
                    print(percentage);

                    Future.delayed(Duration(seconds: 2)).then((value) {
                      pr.hide().then((isHidden) {
                         print(isHidden);
                      });
                      percentage = 0.0;
                    });
                  });
                });
              });

            }),
      ),
    );
  }
}

Complete Example for Switching between to Screens

import 'package:flutter/material.dart';
import 'package:progress_dialog/progress_dialog.dart';

ProgressDialog pr;

void main() {
  runApp(MaterialApp(
    home: FirstScreen(),
  ));
}

class FirstScreen extends StatefulWidget {
  @override
  _FirstScreenState createState() => _FirstScreenState();
}

class _FirstScreenState extends State<FirstScreen> {
  ProgressDialog pr;

  @override
  Widget build(BuildContext context) {
    pr = new ProgressDialog(context);
    pr.style(message: 'Please wait...');

    return Scaffold(
      body: Center(
        child: RaisedButton(
          child: Text('Show dialog and go to next screen',
              style: TextStyle(color: Colors.white)),
          color: Colors.blueAccent,
          onPressed: () {
            pr.show();
            Future.delayed(Duration(seconds: 3)).then((value) {
              pr.hide().whenComplete(() {
                Navigator.of(context).push(CupertinoPageRoute(
                    builder: (BuildContext context) => SecondScreen()));
              });
            });
          },
        ),
      ),
    );
  }
}

class SecondScreen extends StatefulWidget {
  @override
  _SecondScreenState createState() => _SecondScreenState();
}

class _SecondScreenState extends State<SecondScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(child: Text('I am second screen')),
    );
  }
}

Please ignore if the above contains any unoptimized code, it’s just for an example

Demo