fromMap static method
Implementation
static DownloadProcess fromMap(Map<dynamic, dynamic> json) {
//获取第一个值
var status = json["status"] as String;
return DownloadProcess(
current: json["current"] as int,
count: json["count"] as int,
status: ProcessState.values.firstWhere(
(element) => element.toString() == "ProcessState.$status"));
}