Flutter 自定义打开drawer

直接上代码：

leading: Builder(
            builder: (context) => GestureDetector(
                  child: Padding(
                    padding: EdgeInsets.all(8.0),
                    child: CircleAvatar(
                      backgroundImage: NetworkImage(
                          'http://pic75.nipic.com/file/20150821/9448607_145742365000_2.jpg'),
                    ),
                  ),
                  onTap: () => Scaffold.of(context).openDrawer(),
                ),
          ),