Flutter - textFormField Change labelColor on focus

问题:

I am trying to change my labelText color when focused. I can change the text color but not when focused.

I have tried all the hint text colors and label text colors, but nothing helps.

Container(
                padding: EdgeInsets.fromLTRB(15, 10, 15, 0),
                child: TextFormField(
                    cursorColor: Colors.lightGreen,
                  keyboardType: TextInputType.phone,
                  decoration: InputDecoration(
                      labelText: 'Phone Number',
                      hintText: 'Enter a Phone Number',
                    focusedBorder: OutlineInputBorder(
                        borderSide: BorderSide(
                            color: Colors.lightGreen
                        )
                    ),
                    border: OutlineInputBorder(
                        borderSide: BorderSide(
                        )),
                    )
                ),
              ),

Here are images of what is happening.

回答1:

You'd need to have a way determine its focus state and then create a conditional for its color based off of that. This is where a focusNode would be helpful. Construct a new FocusNode off the widget creation, use that as the focusNode property in the TextFormField. Then in color property of the TextStyle property of the TextFormField you could add something like:

  FocusNode myFocusNode = new FocusNode();

    return TextFormField(
      focusNode: myFocusNode,
      decoration: InputDecoration(
        labelText: 'test',
        labelStyle: TextStyle(
          color: myFocusNode.hasFocus ? Colors.blue : Colors.black
        )
      ),
    );

EDIT : Just a quick note, you'll probably need to make sure this is in a StatefulWidget and then add a listener to the focusNode you created and call setState on any events on that focusNode. Otherwise you wont see any changes.