title: How to fetch more data when scroll up FlatList react native?
body: <p>I'm applying lazy load into flatlist. But I only fetch more data when scroll down the lasted item. How can I implement fetch more data when scroll up. I tried onRefresh I dont' know why the list didn't update but the data had changed. 
  Anyone have ideas for this issues?</p>
  
  <pre><code>   &lt;FlatList
        style={props.style}
        renderItem={renderRow}
        data={data}
        keyExtractor={(item, index) =&gt; String(index)}
        onRefresh={onRefresh}
     /&gt;
  
     function onRefresh(){
        dataFetch = fetchMoreData()
        setData([ ...dataFetch, ...data ])
     }
  </code></pre>
  
  <p>Please help me.
  Thank you</p>