緣由：
更新sdk，遇到了更新下載失敗問題：
Fetching https://dl-ssl.google.com/android/repository/addons_list-2.xml
Fetched Add-ons List successfully
Fetching URL: https://dl-ssl.google.com/android/repository/repository-8.xml
Done loading packages.
Fetching https://dl-ssl.google.com/android/repository/addons_list-2.xml
Failed to fetch URL https://dl-ssl.google.com/android/repository/addons_list-2.xml, reason: Connection to https://dl-ssl.google.com refused
Fetched Add-ons List successfully
Fetching URL: https://dl-ssl.google.com/android/repository/repository-8.xml
Failed to fetch URL https://dl-ssl.google.com/android/repository/repository-8.xml, reason: HttpHostConnect Connection to https://dl-ssl.google.com refused
Done loading packages.
遂百度，網上有很多文章有說到這個，但是因為大陸政策問題，像更改hosts文件等方法，我這都沒解決問題，最后還是強大的開源力量啊，開源萬歲，配置步驟如下：
1.啟動 Android SDK Manager ，打開主界面，依次選擇「Tools」、「Options...」，彈出『Android SDK Manager - Settings』窗口；
2.在『Android SDK Manager - Settings』窗口中，在「HTTP Proxy Server」和「HTTP Proxy Port」輸入框內填入mirrors.neusoft.edu.cn和80，並且選中「Force https://... sources to be fetched using http://...」復選框。設置完成后單擊「Close」按鈕關閉『Android SDK Manager - Settings』窗口返回到主界面；
3.依次選擇「Packages」、「Reload」。