Broken Listview

index.ios.js

import React, {Component} from 'react';
import ReactNative from 'react-native';
import * as firebase from 'firebase';
const StatusBar = require('./components/StatusBar');
const ActionButton = require('./components/ActionButton');
const ListItem = require('./components/ListItem');
const styles = require('./styles.js');
import {
  AppRegistry,
  StyleSheet,
  Text,
  View,
  ListView
} from 'react-native';


//  Initialize firebase
const firebaseConfig = {
  apiKey: 'AIzaSyANOkbGi4gEQmzLaY4PKFea_DCM1UHs_LQ',
  authDomain: 'firereactnativedemo.firebaseapp.com',
  databaseURL: 'https://firereactnativedemo.firebaseio.com',
  storageBucket: 'firereactnativedemo.appspot.com',
  serviceAccount: 'FireReactNativeDemo-bb33587a4946.json'
};

const firebaseApp = firebase.initializeApp(firebaseConfig);

class GroceryApp extends Component {
  constructor(props) {
    super(props);
    this.itemsRef = firebaseApp.database().ref();

    this._renderItem = this._renderItem.bind(this);

    var dataSource = new ListView.DataSource({
      rowHasChanged: (r1, r2) => r1 !== r2
    });
    this.state = {
      dataSource: dataSource
    };
  }

  componentDidMount() {
    this.state = {
      dataSource: this.listenForItems(this.itemsRef)
    };
  }

  listenForItems(itemsRef) {
    itemsRef.on('value', snap => {
      // get children as an array
      var items = [];
      snap.forEach(child => {
        items.push({
          title: child.val().title,
          _key: child.key
        });
      });
      // items.push({title: "Pizza", _key: "Pizza"});

      this.state = {
        dataSource: this.state.dataSource.cloneWithRows(items)
      };
    });
  }

  _renderItem(item) {
    return (
      <ListItem item="{item}" onpress={() => {}} />
    );
  }

  render() {
    return (
      <View style={styles.container}>
        <StatusBar title="Grocery List" />
        <ListView
          style={styles.listview}
          dataSource={this.state.dataSource}
          renderRow={this._renderItem} />
        <ActionButton title="Add" onpress={() => { } }/>
      </View>
    );
  }
}

AppRegistry.registerComponent('GroceryApp', () => GroceryApp);