Eclipse出現adt錯誤訊息

打開Eclipse出現以下訊息～

The Android SDK requires Android Developer Toolkit version 21.1.0 or above.

Please update ADT to the latest version.

接著還出現　"installing software has encountered a problem"

解決方式：

Window　→ Preferences →  Install/Update → Available Software Sites

點選 adt 按 edit

將http://dl-ssl.google.com/android/eclipse/

改成 https://dl-ssl.google.com/android/eclipse/