showCupertinoModalPopup(
        context: context,
        builder: (context) {
          return CupertinoActionSheet(
            actions: <Widget>[
              CupertinoActionSheetAction(
              child: Text('保存图片'),
              onPressed: () {

              },
              isDefaultAction: true,
              ),
            ],
            cancelButton: CupertinoActionSheetAction(
              child: Text('取消'),
              onPressed: () {
                Navigator.of(context).pop();
              },
            ),
          );
        }