Unable to fetch data correctly from JSON array in React Native

  showPosts = async () => {

    var userID = await AsyncStorage.getItem('userID');

    fetch(strings.baseUri+"getPostWithUserID", {
        method: 'POST',
        headers: {
           Accept: 'application/json',
           'Content-Type': 'application/json'
        },
        body: JSON.stringify({ 
            "user_id": userID
        })
        })
        .then((response) => response.json())
        .then((responseJson) => {

        let jsonObj = JSON.parse(JSON.stringify(responseJson));

        if (jsonObj.status=="true") {

            this.setState({ 
                data: responseJson.data, 
                imageSrc: responseJson.data[0].imgSrc, 
                post_type: responseJson.data[0].post_type,
                videoSrc: responseJson.data[0].video,
            });
        }        
    })
        .catch((error) => {
            console.error(error);
        });
  }

I'm fetching data from api and then using it in Flatlist.

This is what I get when I alert(responseJson.data). Now, my responseJson.data[0].imgSrc and responseJson.data[0].video iterates each object and I'm able to display it on my screen via Flatlist. But this isn't the case in responseJson.data[0].post_type. responseJson.data[0].post_type fetches only post_type of first object from the JSON array. I've also added this.state.post_type in extraData.

Please tell me how to access data from Json array and then use it in Flatlist.

UPDATED CODE

    <FlatList 
        data={this.state.data}
        renderItem={ ({item,index}) =>  this._renderItem(item,index)  }
        extraData={[ this.state.data, this.state.checked, this.state.post_type ]}
    />

_renderItem = ( item, index ) => {

return(

{ item.post_type == "image" ? 

                    <Image 
                        //source={this.props.item.image} 
                        source={image}}
                        //source={{ uri: strings.sourceUri+"userimage/"+item.imgSrc }}
                        style={styles.photo}
                    />

                    :

                    <Video 
                        source={video}
                        ref={(ref) => { this.player = ref }}   
                        style={{  width: 300,  height: 350,  }}
                    />

       }
     ); 
}