onChange TextField move cursor to start in flutter

Question

I try to check input with onChange method in TextField but after replacing text with TextEditingController cursor move to start of TextField.

This problem occurs only on the Android platform.

Code

TextField(
controller: textEditController,
onChanged: (content) {
                    textEditController.text = checkNumber(content);
                  },)

flutter version

[✓] Flutter (Channel master, v1.2.2-pre.41, on Mac OS X 10.14.3 18D109, locale
    en-IR)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)

Answer 1

Set the selection using the TextEditingController

TextField(
controller: textEditController,
onChanged: (content) {
  textEditController..text = checkNumber(content)
                    ..selection = TextSelection.collapsed(offset: 0);
  },
)

Answer 2

The accepted solution didn't work for me - as I was setting both text and selection I needed to instead set value.

The TextEditingController class documentation states:

The text or selection properties can be set from within a listener added to this controller. If both properties need to be changed then the controller's value should be set instead.

The documentation also has a relevant example that includes the following:

void initState() {
  _controller.addListener(() {
    final text = _controller.text.toLowerCase();
    _controller.value = _controller.value.copyWith(
      text: text,
      selection: TextSelection(baseOffset: text.length, extentOffset: text.length),
      composing: TextRange.empty,
    );
  });
  super.initState();
}

This forces the entered text to be lower case and keeps the cursor at the end of the input.