下载SDK总是会出现如下错误：
Failed to fetch URL /android/repository/addons_list-1.xml.
解决方法:修改C:\Windows\System32\drivers\etc\hosts文件。

添加一行：
74.125.237.1
这里需要注意的是hosts文件是只读的，我们没有权限修改，需要我们将hosts 文件复制到桌面或者其他地方，然后修改，代码如下：
# Copyright (c) 1993-2009 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
# 102.54.94.97 # source server
# 38.25.63.10 # x client host
# localhost name resolution is handled within DNS itself.
# 127.0.0.1 localhost
# ::1 localhost
//亲，就是增加这一句哦
74.125.237.1
然后保存，复制修改后的hosts文件到C:\Windows\System32\drivers\etc 目录，替换文件就好！我们再次下载SDK的时候就会成功了，如下图：
这样，大功告成！。