颜色转化工具

//////////////////////////// 颜色转化工具

extension  hex on String{
  Color get color { // 将 #ff0000 转化成颜色 // 如果不满足条件则为透明颜色
    return ColorHex.fromHexString(this);
 }
}


/////////////////////////////////////////////////////////////
import 'dart:ui';
class ColorTool {
  ///直接使用 0xffffff
  static Color colorHex({required int hex,double? alpha}) {
    int r = (hex & 0xFF0000) >> 16;
    int g = (hex & 0xFF00) >> 8;
    int b = (hex & 0xFF);
    return Color.fromRGBO(r, g, b, alpha??1);
  }
 ///用于通过服务器返回颜色 #ffffff 这种颜色的转化
  static colorWithHexString({required String str,double? alpha}) {
    if (str.isEmpty) return ColorTool.clear;

    String cString = str.toUpperCase(); //转为大写

    if (cString.length < 6) return ColorTool.clear;

    var m = cString.startsWith("0X");

    var n = cString.startsWith("#");

    if (m) {
      cString = cString.substring(2);
    } else if (n) {
      cString = cString.substring(1);
    }
    if (cString.length != 6) return ColorTool.clear;
    var start = 0;
    var end = 2;
    String r = cString.substring(start, end);
    start = start + 2;
    end = start + 2;
    String g = cString.substring(start, end);
    start = start + 2;
    end = start + 2;
    String b = cString.substring(start, end);
    return Color.fromRGBO(_hexToInt(r), _hexToInt(g), _hexToInt(b) , alpha??1);
  }

  static Color clear = Color.fromRGBO(0, 0, 0, 0);

  static int _hexToInt(String hex) {
    int val = 0;
    int len = hex.length;
    for (int i = 0; i < len; i++) {
      int hexDigit = hex.codeUnitAt(i);
      if (hexDigit >= 48 && hexDigit <= 57) {
        val += (hexDigit - 48) * (1 << (4 * (len - 1 - i)));
      } else if (hexDigit >= 65 && hexDigit <= 70) {
        // A..F
        val += (hexDigit - 55) * (1 << (4 * (len - 1 - i)));
      } else if (hexDigit >= 97 && hexDigit <= 102) {
        // a..f
        val += (hexDigit - 87) * (1 << (4 * (len - 1 - i)));
      } else {
        throw new FormatException("Invalid hexadecimal value");
      }
    }
    return val;
  }
}
extension ColorHex on Color {
  static Color fromHex(int hex,{double? alpha}){ //使用拓展
    return ColorTool.colorHex(hex: hex,alpha: alpha);
  }
  static Color fromHexString(String? hexStr,{double? alpha}){
    if(hexStr == null){
      return ColorTool.clear;
    }
    return ColorTool.colorWithHexString(str: hexStr,alpha: alpha);
  }
}