title: Flatlist doesn't display data from firebase
body: <p>I'm trying to display one item in the Flatlist but it's doesn't display anything. Even the items outside of Flatlist aren't displayed. I don't ussually use Class componets so maybe I have missed something?</p>
  <pre class="lang-js prettyprint-override"><code>static navigationOption = ({ navigation }) =&gt; {
          return {
            scannedkey: navigation.getParam(&quot;itemId&quot;, null)
          }
        }
       
     
      constructor(props){
          super(props);
          this.state={ 
          productlist:[],
  
          
          } }
          
      async componentDidMount(scannedkey){
          
          firebase.database().ref(`product/${scannedkey}`).on(
            &quot;value&quot;,
            (snapshot) =&gt; {
              var list = [];
              snapshot.forEach((child) =&gt; {
                list.push({
                  key: child.key,
                  title: child.title,
                  //details: child.val().details,
                  //price: child.val().price
                });
              });
          
              this.setState({ productlist: list });
            },
            (error) =&gt; console.error(error)
          );
      }
    componentWillUnmount() {
        if (this.valuelistener_) {
          this.valueRef_.off(&quot;value&quot;, this.valuelistener_)
        }}
      
    render() {
      console.log(this.state.productlist)
   return(
       &lt;View style={styles.container}&gt;
         &lt;Text&gt;Hey&lt;/Text&gt;
        &lt;Text&gt;{this.state.productlist.title}&lt;/Text&gt;
       &lt;/View&gt;
   );}}
  </code></pre>
  <p>This is what Error I get :</p>
  <pre><code>Setting a timer for a long period of time, i.e. multiple minutes, is a performance and correctness issue on Android as it keeps the timer module awake, and timers can only be called when the app is in the foreground. See https://github.com/facebook/react-native/issues/12981 for more info.
  (Saw setTimeout with duration 392608ms)
  at node_modules\react-native\Libraries\LogBox\LogBox.js:117:10 in registerWarning
  at node_modules\react-native\Libraries\LogBox\LogBox.js:63:8 in warnImpl
  at node_modules\react-native\Libraries\LogBox\LogBox.js:36:4 in console.warn
  at node_modules\expo\build\environment\react-native-logs.fx.js:18:4 in warn
  at node_modules\react-native\Libraries\Core\Timers\JSTimers.js:226:6 in setTimeout
  at node_modules\@firebase\database\dist\index.esm.js:99:8 in MemoryStorage
  </code></pre>
  <p>I would be grateful if you help me find the solution on how to fix it.</p>