flutter_wisetronic/lib/widgets/general/read_more_text.dart

import 'package:flutter/gestures.dart';
import 'package:flutter/material.dart';

enum TrimMode {
  Length,
  Line,
}

class ReadMoreText extends StatefulWidget {
  const ReadMoreText(
      this.data, {
        Key key,
        this.trimExpandedText = ' read less',
        this.trimCollapsedText = ' ...read more',
        this.colorClickableText,
        this.trimLength = 240,
        this.trimLines = 2,
        this.trimMode = TrimMode.Length,
        this.style,
        this.textAlign,
        this.textDirection,
        this.locale,
        this.textScaleFactor,
        this.semanticsLabel,
      })  : assert(data != null),
        super(key: key);

  final String data;
  final String trimExpandedText;
  final String trimCollapsedText;
  final Color colorClickableText;
  final int trimLength;
  final int trimLines;
  final TrimMode trimMode;
  final TextStyle style;
  final TextAlign textAlign;
  final TextDirection textDirection;
  final Locale locale;
  final double textScaleFactor;
  final String semanticsLabel;

  @override
  ReadMoreTextState createState() => ReadMoreTextState();
}

const String _kEllipsis = '\u2026';

const String _kLineSeparator = '\u2028';

class ReadMoreTextState extends State<ReadMoreText> {
  bool _readMore = true;

  void _onTapLink() {
    setState(() => _readMore = !_readMore);
  }

  @override
  Widget build(BuildContext context) {
    final DefaultTextStyle defaultTextStyle = DefaultTextStyle.of(context);
    TextStyle effectiveTextStyle = widget.style;
    if (widget.style == null || widget.style.inherit) {
      effectiveTextStyle = defaultTextStyle.style.merge(widget.style);
    }

    final textAlign =
        widget.textAlign ?? defaultTextStyle.textAlign ?? TextAlign.start;
    final textDirection = widget.textDirection ?? Directionality.of(context);
    final textScaleFactor =
        widget.textScaleFactor ?? MediaQuery.textScaleFactorOf(context);
    final overflow = defaultTextStyle.overflow;
    final locale =
        widget.locale ?? Localizations.localeOf(context);

    final colorClickableText =
        widget.colorClickableText ?? Theme.of(context).accentColor;

    TextSpan link = TextSpan(
      text: _readMore ? widget.trimCollapsedText : widget.trimExpandedText,
      style: effectiveTextStyle.copyWith(
        color: colorClickableText,
      ),
      recognizer: TapGestureRecognizer()..onTap = _onTapLink,
    );

    Widget result = LayoutBuilder(
      builder: (BuildContext context, BoxConstraints constraints) {
        assert(constraints.hasBoundedWidth);
        final double maxWidth = constraints.maxWidth;

        // Create a TextSpan with data
        final text = TextSpan(
          style: effectiveTextStyle,
          text: widget.data,
        );

        // Layout and measure link
        TextPainter textPainter = TextPainter(
          text: link,
          textAlign: textAlign,
          textDirection: textDirection,
          textScaleFactor: textScaleFactor,
          maxLines: widget.trimLines,
          ellipsis: overflow == TextOverflow.ellipsis ? _kEllipsis : null,
          locale: locale,
        );
        textPainter.layout(minWidth: constraints.minWidth, maxWidth: maxWidth);
        final linkSize = textPainter.size;

        // Layout and measure text
        textPainter.text = text;
        textPainter.layout(minWidth: constraints.minWidth, maxWidth: maxWidth);
        final textSize = textPainter.size;

        print('linkSize $linkSize textSize $textSize');

        // Get the endIndex of data
        bool linkLongerThanLine = false;
        int endIndex;

        if (linkSize.width < maxWidth) {
          final pos = textPainter.getPositionForOffset(Offset(
            textSize.width - linkSize.width,
            textSize.height,
          ));
          endIndex = textPainter.getOffsetBefore(pos.offset);
        }
        else {
          var pos = textPainter.getPositionForOffset(
            textSize.bottomLeft(Offset.zero),
          );
          endIndex = pos.offset;
          linkLongerThanLine = true;
        }

        var textSpan;
        switch (widget.trimMode) {
          case TrimMode.Length:
            if (widget.trimLength < widget.data.length) {
              textSpan = TextSpan(
                style: effectiveTextStyle,
                text: _readMore
                    ? widget.data.substring(0, widget.trimLength)
                    : widget.data,
                children: <TextSpan>[link],
              );
            } else {
              textSpan = TextSpan(
                style: effectiveTextStyle,
                text: widget.data,
              );
            }
            break;
          case TrimMode.Line:
            if (textPainter.didExceedMaxLines) {
              textSpan = TextSpan(
                style: effectiveTextStyle,
                text: _readMore
                    ? widget.data.substring(0, endIndex) +
                    (linkLongerThanLine ? _kLineSeparator : '')
                    : widget.data,
                children: <TextSpan>[link],
              );
            } else {
              textSpan = TextSpan(
                style: effectiveTextStyle,
                text: widget.data,
              );
            }
            break;
          default:
            throw Exception(
                'TrimMode type: ${widget.trimMode} is not supported');
        }

        return RichText(
          textAlign: textAlign,
          textDirection: textDirection,
          softWrap: true,
          //softWrap,
          overflow: TextOverflow.clip,
          //overflow,
          textScaleFactor: textScaleFactor,
          text: textSpan,
        );
      },
    );
    if (widget.semanticsLabel != null) {
      result = Semantics(
        textDirection: widget.textDirection,
        label: widget.semanticsLabel,
        child: ExcludeSemantics(
          child: result,
        ),
      );
    }
    return result;
  }
}