On my login page, I have two TextField, one for username(obscureText: false,), one for password(obscureText: true,).

after finish the username input, I click in the password textfield, the keyboard will disappear even if the password textfield get the focus. It will appear when click again! Then, click username textfield again, the keyboard not appear also.

I have open the system secure keyboard:
To enable Secure Keyboard, go to [Settings] > [Additional Settings] > [Keyboard & Input Method] and toggle on [Use Secure Keyboard When Entering a Password].

If I close the system secure keyboard, everything is ok!!

this is my flutter doctor -v

[√] Flutter (Channel stable, 1.20.4, on Microsoft Windows [Version 10.0.18362.1082], locale zh-CN)

[√] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
[√] Android Studio (version 3.5)
[√] IntelliJ IDEA Ultimate Edition (version 2018.3)
[√] Connected device (1 available)