Flutter TextField 文字颜色

问题：

Flutter 中 TextField 根据文字改变颜色

例如 “I want an apple” , “apple” 就自动变为蓝色。

解决方法：

继承TextEditingController来实现：

class FruitColorizer extends TextEditingController{
  final Map<String, TextStyle> mapping;
  final Pattern pattern;

  FruitColorizer(this.mapping) : pattern = RegExp(mapping.keys.map((key) => RegExp.escape(key)).join('|'));
  @override
  TextSpan buildTextSpan({TextStyle style, bool withComposing}) {
    List<InlineSpan> children = [];
    // splitMapJoin is a bit tricky here but i found it very handy for populating children list
    text.splitMapJoin(pattern, 
      onMatch: (Match match) {
        children.add(TextSpan(text: match[0], style: style.merge(mapping[match[0]])));
      },
      onNonMatch: (String text) {
        children.add(TextSpan(text: text, style: style));
      },
    );
    return TextSpan(style: style, children: children);
  }
}

使用时，就可以根据关键字自定义颜色：

TextField(
  style: TextStyle(fontSize: 32),
  controller: FruitColorizer({
    'apple': TextStyle(color: Colors.green, decoration: TextDecoration.underline),
    'orange': TextStyle(color: Colors.orange, shadows: kElevationToShadow[2]),
  }),
),