问为什么Flatlist中的图像有时不能渲染？

EN

renderItem = ({ item, index }) => {
  return(
    //console.log(item)
    <TouchableHighlight onPress={this.props.toggleView.bind(this, index)} > 
      <View >
      <Image source={{uri: item.images.thumbnail.url, cache:'force-cache'}} style={styles.item} resizeMode={"resize"}/>      
      </View>
      </TouchableHighlight>
   ) 
 }


render(){
return(
        <FlatList
        ref={(ref) => { this._flatList = ref; }}
        data={this.props.profileMedia}
        onScroll={this.handleScroll}
        renderItem={this.renderItem.bind(this)}
        numColumns={3}
        ListHeaderComponent={this.renderHeader}
        ListFooterComponent={this.renderFooter}
        columnWrapperStyle={{justifyContent: 'flex-start'}}
        contentOffset = {{x: 0, y:this.props.scrollPosition}}
        keyExtractor={item => item.id}
        initialNumToRender={12}
      />
  )
 }