How can i limit textinput lines in flutter-CodePudding

I use TextFormField Widget, and I set the maxlines parameter to 5. But I was able to keep typing. I want to limit input when maxline is reached. what should I do?

TextFormField(
              controller: _contextController,
              cursorColor: Colors.white,
              textAlign: TextAlign.center,
              focusNode: _contextFocus,
              keyboardType: TextInputType.multiline,
              minLines: 1,
              maxLines: 5,
              inputFormatters: [F],
              decoration: InputDecoration(
                  fillColor: Color(0xBD000000),
                  filled: true,
                  enabledBorder: InputBorder.none,
                  focusedBorder: InputBorder.none,
                  border: InputBorder.none,
                  errorBorder: InputBorder.none,
                  contentPadding: EdgeInsets.all(20),
                  hintText: _contextHint,
                  hintStyle: TextStyle(color: Colors.white)),
            ),

CodePudding user response：

Max Lines property is not for that purpose. As per the official documentation, maxlines optional a maximum number of lines for the text to span, wrapping if necessary. If the text exceeds the given number of lines, it will be truncated according to overflow.

You can use the maxLength property for restrict users to exceed the specified length.

TextFormField(
   maxLength: 130,
),

CodePudding user response：

maxLines limits the height of the TextField, not the length of the content. maxLength does limit the length of the content, but by number of characters, not number of lines. There was similar question added here: How to limit the number of inputable lines in a textField

CodePudding user response：

Here is the code

class MaxLinesInputFormatters extends TextInputFormatter {
  MaxLinesInputFormatters(this.maxLines)
      : assert(maxLines == null || maxLines == -1 || maxLines > 0);

  final int maxLines;

  @override
  TextEditingValue formatEditUpdate(
    TextEditingValue oldValue,
    TextEditingValue newValue,
  ) {
    if (maxLines != null && maxLines > 0) {
      final regEx = RegExp("^.*((\n?.*){0,${maxLines - 1}})");
      String newString = regEx.stringMatch(newValue.text) ?? "";

      final maxLength = newString.length;
      if (newValue.text.runes.length > maxLength) {
        final TextSelection newSelection = newValue.selection.copyWith(
          baseOffset: math.min(newValue.selection.start, maxLength),
          extentOffset: math.min(newValue.selection.end, maxLength),
        );
        final RuneIterator iterator = RuneIterator(newValue.text);
        if (iterator.moveNext())
          for (int count = 0; count < maxLength;   count)
            if (!iterator.moveNext()) break;
        final String truncated = newValue.text.substring(0, iterator.rawIndex);
        return TextEditingValue(
          text: truncated,
          selection: newSelection,
          composing: TextRange.empty,
        );
      }
      return newValue;
    }
    return newValue;
  }
}

Usage:

         TextFormField(
                cursorColor: Colors.white,
                textAlign: TextAlign.center,
                focusNode: _contextFocus,
                keyboardType: TextInputType.multiline,
                minLines: 1,
                maxLines: 5,
                inputFormatters: [MaxLinesInputFormatters(5)],
                decoration: InputDecoration(
                  fillColor: Color(0xBD000000),
                  filled: true,
                  enabledBorder: InputBorder.none,
                  focusedBorder: InputBorder.none,
                  border: InputBorder.none,
                  errorBorder: InputBorder.none,
                  contentPadding: EdgeInsets.all(20),
                  hintText: _contextHint,
                  hintStyle: TextStyle(
                    color: Colors.white,
                  ),
                ),
              ),

CodePudding user response：

You can't limit it by lines you have to limit user by the length of the word count like this.

 inputFormatter: [
                  LengthLimitingTextInputFormatter(10),
                ],

replace 10 with your word count.