ADT无法生成R.java文件解决方法

I had the problem too. There is a new component in the Tools folder called "Android SDK Build-tools"that needs to be installed.

Step 1

Open the Android SDK Manager

Step 2

Select the newly added Build Tools and install. (If problem stays then go to Project Properties => Java Build Path => Order and Export and check Android Private Libraries, then clean and build project.

It may be necessary to repeat the process, restart the SDK Manager after the update and make sure it looks like this (all tools installed):

More info:https://groups.google.com/forum/?fromgroups=#!topic/android-developers/rCaeT3qckoE%5B1-25-false%5D