android-pulltorefresh 下拉载入中使用gif动图

效果预览：

xml布局

<com.handmark.pulltorefresh.library.PullToRefreshListView xmlns:android="https://schemas.android.com/apk/res/android"
    xmlns:ptr="https://schemas.android.com/apk/res-auto"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:divider="#00000000"
    android:cacheColorHint="#00000000"
    android:listSelector="#00000000"
    android:fastScrollEnabled="true"
     ptr:ptrHeaderTextColor="@color/gray" 
     ptr:ptrAnimationStyle="louisAnimationStyle"
    /><com.handmark.pulltorefre