成员变量 类型: String # static readonly failed LoadStatus.failed，加载失败 Default Value: 'failed' 类型: String # static readonly loaded LoadStatus.loaded，加载完毕 Default Value: 'loaded' 类型: String # static readonly loading LoadStatus.loading，加载中 Default Value: 'loading' 类型: String # static readonly notLoaded LoadStatus.notLoaded，未加载 Default Value: 'not-loaded'
