添加了注释，完善了参数校验及空值处理

app/src/main/java/com/sw/inbound/ext/CommonExt.kt

@@ -33,26 +33,35 @@ private fun Double.roundToDouble(decimalPlaces: Int): Double {
     return kotlin.math.round(this * factor) / factor
 }
 
+fun Double?.toSafeString(unitName: String?): String {
+    if (this == null || this == 0.0) return ""
+    val decimalPlaces = getDecimalPlaces(unitName)
+    return "%.${decimalPlaces}f".format(this)
+}
+
 fun Double?.toSafeDouble(unitName: String?): Double {
     if (this == null || this == 0.0) return 0.0
 
-    val decimalPlaces = when (unitName) {
-        "斤", "克", "公斤", "升" -> 2
-        else -> 0
-    }
-
+    val decimalPlaces = getDecimalPlaces(unitName)
     return roundToDouble(decimalPlaces)
 }
 
 fun Double?.toSafeFloat(unitName: String?): Float {
     if (this == null || this == 0.0) return 0f
 
+    val decimalPlaces = getDecimalPlaces(unitName)
+    return roundToDouble(decimalPlaces).toFloat()
+}
+
+/**
+ * 通过单位判断小数
+ */
+private fun getDecimalPlaces(unitName: String?): Int {
     val decimalPlaces = when (unitName) {
         "斤", "克", "公斤", "升" -> 2
         else -> 0
     }
-
-    return roundToDouble(decimalPlaces).toFloat()
+    return decimalPlaces
 }
 
 fun BigDecimal.toFormattedString(): String {