fragment 中不能和activity一样通过配置adjustresize设置来检测软键盘
mRoot = getActivity().getWindow().getDecorView();
mRoot.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
@Override
public void onGlobalLayout() {
Rect rect = new Rect();
mRoot.getWindowVisibleDisplayFrame(rect);
int rootInvisibleHeight = mRoot.getRootView().getHeight()-rect.bottom;
}
});