FloatMath is deprecated

[JackyDuong]

I have these lines when i use Proguard to signed my apk

Warning:com.handmark.pulltorefresh.library.PullToRefreshWebView: can't find referenced method 'float floor(float)' in library class android.util.FloatMath
Warning:com.handmark.pulltorefresh.library.PullToRefreshWebView$InternalWebViewSDK9: can't find referenced method 'float floor(float)' in library class android.util.FloatMath

I added the line below to my proguard but it doesn't work

-keep public class android.util.FloatMath

Does someone have a solution about that ?