flutter Text文本更多和收起功能

class TextSpanShow extends StatefulWidget {
  final String text;
  final Color colorTest;
  final Color ellipsisColorTest;
  final Color moreBackgroundTest;
  final Color moreContainerColor;
  final int mMaxLine;
  final bool showColor;
  final TextStyle styleText;
  final double textSpanWidth;
  final double textSpanHeight;
  const TextSpanShow(
    this.text, {
    Key key,
    this.colorTest = Colors.black,
    this.ellipsisColorTest,
    this.mMaxLine = 3, this.styleText, this.moreBackgroundTest, this.showColor, this.textSpanWidth, this.textSpanHeight, this.moreContainerColor,
  }) : super(key: key);

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

class _TextSpanShowState extends State<TextSpanShow> {
  bool mIsExpansion = false;




  @override
  Widget build(BuildContext context) {
    return Container(
      width: widget.textSpanWidth ?? null,
      height: widget.textSpanHeight ?? null,
      color: widget.moreContainerColor ?? null,
      child: richText(widget.text,),
    );
  }

  Widget richText(String _text) {
    if (IsExpansion(_text)) {
     //如果需要截断
      if (mIsExpansion) {
        return Stack(
          children: <Widget>[
            new Text(
              _text,
              textAlign: TextAlign.left,
              style:widget.styleText?? TextStyle(color: widget.colorTest),
            ),
            Positioned(
              right: 0,
              bottom: 0,
              child: Container(
                decoration: BoxDecoration(color: Colors.red),
                child: GestureDetector(
                  onTap: () {
                    _isShowText();
                  },
                  child: Text("收起<",
                      style: TextStyleFactory.styleSubtitle3(
                          context, 12, Colors.blue)),
                ),
              ),
            ),
          ],
        );
      } else {
        return Stack(
          children: <Widget>[
            Padding(
              padding: EdgeInsets.all(0),
              child: Text(
                _text,
                maxLines: widget.mMaxLine,
                textAlign: TextAlign.left,
                overflow: TextOverflow.ellipsis,
                style:widget.styleText?? TextStyle(color: widget.ellipsisColorTest??widget.colorTest),
              ),
            ),
            Positioned(
              right: 0,
              bottom: 0,
              child: Container(
                  color: widget.moreContainerColor??Color.fromARGB(255, 250, 250, 250),
                  child: Row(
                    children: [
                      Container(
                        child: Text(
                          "...  ",
                          style:widget.styleText?? TextStyle(color: widget.moreBackgroundTest),
                        ),
                      ),
                      GestureDetector(
                        child: Text("更多>",
                            style: TextStyleFactory.styleSubtitle3(
                                context, 12, Colors.blue)),
                        onTap: () {
                          _isShowText();
                        },
                      ),
                    ],
                  )),
            ),
          ],
        );
      }
    } else {
      return Text(
        _text,
        maxLines: widget.mMaxLine,
        textAlign: TextAlign.left,
        overflow: TextOverflow.ellipsis,
        style:widget.styleText?? TextStyle(color: Colors.black),
      );
    }
  }

  bool IsExpansion(String text) {
    TextPainter _textPainter = TextPainter(
        maxLines: widget.mMaxLine,
        text: TextSpan(
            text: text, style: TextStyle(fontSize: 16.0, color: Colors.black)),
        textDirection: TextDirection.ltr)
      ..layout(maxWidth: Screen.width, minWidth: Screen.width);
    if (_textPainter.didExceedMaxLines) {
      //这里判断 文本是否截断
      return true;
    } else {
      return false;
    }
  }

  void _isShowText() {
    if (mIsExpansion) {
      //关闭了
      setState(() {
        mIsExpansion = false;
      });
    } else {
      setState(() {
        mIsExpansion = true;
      });
    }
  }
}