ScrollToEnd after update data for Flatlist

Question

I'm making a chat box with Flatlist. I want to add a new item to data then scroll to bottom of list. I use scrollToEnd method but it did not work. How can I do this?

<FlatList
        ref="flatList"
        data={this.state.data}
        extraData = {this.state}
        renderItem={({item}) => <Text style={styles.chatFlatListItem}>{item.chat}</Text>}
/>

AddChat(_chat){
    var arr = this.state.data;
    arr.push({key: arr.length, chat: _chat});
    var _data = {};
    _data["data"] = arr;
    this.setState(_data);
    this.refs.flatList.scrollToEnd();
 }

Answer 1

I found a better solution,scrollToEnd() is not working because it is triggered before the change is made to the FlatList.
Since it inherits from ScrollView the best way here is to call scrollToEnd() in onContentSizeChange like so :

<FlatList
            ref = "flatList"
            onContentSizeChange={()=> this.refs.flatList.scrollToEnd()} /> 

Answer 2

Thanks @Kernael, just add a timeout like so:

setTimeout(() => this.refs.flatList.scrollToEnd(), 200)

Answer 3

Change your code as below. The ref is modified and It's better to use getItemLayout in your FlatList according to this.

AddChat(_chat){
    var arr = this.state.data;
    arr.push({key: arr.length, chat: _chat});
    var _data = {};
    _data["data"] = arr;
    this.setState(_data);
    this.flatList.scrollToEnd();
 }

<FlatList
    ref={elm => this.flatList = elm}
    data={this.state.data}
    extraData = {this.state}
    renderItem={({item}) => <Text style={styles.chatFlatListItem}>{item.chat}</Text>}
    getItemLayout={(data, index) => (
      {length: ITEM_HEIGHT, offset: ITEM_HEIGHT * index, index}
    )}
/>

Note: Replace the ITEM_HEIGHT with the real value of height of your list items.