Android自定义SmartDateFormat实现下拉刷新与上拉加载动画效果

  
    
 import android.content.Context;
    
 import android.graphics.drawable.AnimationDrawable;
    
 import android.support.annotation.NonNull;
    
 import android.support.annotation.Nullable;
    
 import android.util.AttributeSet;
    
 import android.view.View;
    
 import android.widget.ImageView;
    
 import android.widget.LinearLayout;
    
  
    
 import com.scwang.smartrefresh.layout.api.RefreshHeader;
    
 import com.scwang.smartrefresh.layout.api.RefreshKernel;
    
 import com.scwang.smartrefresh.layout.api.RefreshLayout;
    
 import com.scwang.s