http://stackoverflow.com/questions/12628439/how-can-i-enable-javadoc-for-the-android-support-library/12629379#12629379
I created a file android-support-v4.jar.properties in the libs folder. It contains the lines:
在lib中新建android-support-v4.jar.properties的文件
doc=c:\\[path-to-android-sdk]\\docs\\reference
src=C:\\[path-to-android-sdk]\\extras\\android\\support\\v4\\src在文件中写入如上的内容,当然前提条件是你已经下载了对应的doc和src
Next right-click the project, select refresh, then you'll get javadoc support. You don't really need the doc entry--the src entry already contains the javadocs.
刷新或重启eclipse,你就可以看到doc的支持和查看源代码.