话不多说直接上代码：
/**
* target 要转换的数字
* postion 要保留的位数
* isCrop true 直接裁剪 false 四舍五入
*/
String formartNum(num target, int postion, {bool isCrop = false}) {
String t = target.toString();
// 如果要保留的长度小于等于0 直接返回当前字符串
if (postion < 0) {
return t;
}
if (t.contains(".")) {
String t1 = t.split(".").last;
if (t1.length >= postion) {
if (isCrop) {
// 直接裁剪
return t.substring(0, t.length - (t1.length - postion));
} else {
// 四舍五入
return target.toStringAsFixed(postion);
}
} else {
// 不够位数的补相应个数的0
String t2 = "";
for (int i = 0; i < postion - t1.length; i++) {
t2 += "0";
}
return t + t2;
}
} else {
// 不含小数的部分补点和相应的0
String t3 = postion>0?".":"";
for (int i = 0; i < postion; i++) {
t3 += "0";
}
return t + t3;
}
}
测试：
log(formartNum(10, 0));
log(formartNum(10, 1));
log(formartNum(100.0, 2));
log(formartNum(10.999, 2, isCrop: true));
log(formartNum(10.991, 1, isCrop: true));
log(formartNum(10.001, 5));
log(formartNum(10.008, 6));
打印结果：
flutter: 10
flutter: 10.0
flutter: 100.00
flutter: 10.99
flutter: 10.9
flutter: 10.00100
flutter: 10.008000
