TextField is gaining focus after navigating to another screen

In my project I've wrapped the whole MaterialApp in a GestureDetector which is supposed to dismiss keyboard when user tapped the screen, using this piece of code

FocusScope.of(context).unfocus()

After testing multiple scenarios it wasn't working so I decided to do it the wrong way

FocusScope.of(context).requestFocus(FocusNode())

But now I'm experiencing another issue. Here is my code for a simple screen which is instantiated by MaterialApp's routes builder.

import 'package:flutter/material.dart';

class TestScreen extends StatefulWidget {
  @override
  _TestScreenState createState() => _TestScreenState();
}

class _TestScreenState extends State<TestScreen> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Column(
        children: <Widget>[
          TextFormField(),
          FlatButton(
              onPressed: () => Navigator.push(context,
                  MaterialPageRoute(builder: (context) => TestScreen())),
              child: Text('Test'))
        ],
      ),
    );
  }
}

The steps to reproduce error is: 1-Start editing TextField. 2-Unfocus TextField by tapping somewhere on screen. 3-Tap on button to navigate to another screen. This is the result:

This behavior is not happening when I'm trying to unfocus TextField by pressing keyboard's done button. According to the source code when done button is pressed, TextField is calling clearComposing on TextEditingController. I even tried that but got no luck. How can I fix it? Does anyone else have better solution to handle dismissing keyboard in Flutter?

Also here is my flutter doctor result:

Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, v1.17.5, on Mac OS X 10.15.5 19F101, locale en-US)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
[✓] Android Studio (version 4.0)
[✓] VS Code (version 1.47.3)
[✓] Connected device (2 available)

• No issues found!

Finally this line of code solved my issue:

WidgetsBinding.instance.focusManager.primaryFocus?.unfocus();

I'm not aware of side effects of it but It's working for now.