Hey @kangwang1988,

what's your use case for a customized keyboard? From the screenshots It looks like you could just set the keyboardType [1] of the TextField to something like const TextInputType.numberWithOptions(decimal: true) and rely on the system keyboard.

[1] https://master-docs-flutter-io.firebaseapp.com/flutter/material/TextField/keyboardType.html

@goderbauer
It's not only a number keyboard, but a customized one. As below:

This still feels like a numeric keyboard. The more idiomatic way of doing this would probably be to show the properly configured (numeric) system keyboard and display a custom view with the custom keys hovering just above the keyboard (which seem to just be the "hide keyboard" key and the yellow key). This way would respect the keyboard choice that the user made on the system, e.g. some accessibility users may have chosen a morse keyboard to enter information that way. With this approach you're making life more difficult for them.

Your current implementation would also break people who have a physical keyboard attached to their device because you're no longer opening an input connection with the OS. A better way to implement this may be to add a new type none to TextInputType [1], which you can pass in to the TextField's keyboardType property [2]. This type should still properly configure an input connection to allow input from physical keyboards, but prevent the on-screen keyboard from coming up on the native side (I haven't looked into how to do that).

Even better: iOS seems to have support for "Custom Views for Data Input" [3], which seems to be what you want. It would be cool if we could make that API useable from flutter as well. We'd have to check if there's an Android equivalent. This solution would require some more design work. Might be worth filing an issue for it.

[1] https://master-docs-flutter-io.firebaseapp.com/flutter/services/TextInputType-class.html
[2] https://master-docs-flutter-io.firebaseapp.com/flutter/material/TextField/keyboardType.html
[3] https://developer.apple.com/library/archive/documentation/StringsTextFonts/Conceptual/TextAndWebiPhoneOS/InputViews/InputViews.html

https://github.com/Im-Kevin/cool_ui
This is the plugin I wrote. Custom keyboard can be implemented based on TextField

I am closing this for now as there hasn't been any activity.