title: undefined is not an object (evaluating function) in React Native
body: <p>Hi I'm new in react native and I'm working on a sample chat app.Currently I'm facing a basic problem of navigation. Any help is appreciated.</p>
  
  <p>I need to navigate from chat list to chat screen on click. Im using android emulator using Android studio. For this I wrote the script. But Im getting error when I click on a right_arrow having onPress function defined in the following code,</p>
  
  <pre><code>onContactPress = (item) =&gt;{
        Alert.alert();        
  }    
  
  renderFlatListItem({item}) {
    return (
      &lt;View style={styles.container}&gt;
        &lt;TouchableOpacity onPress={() =&gt; this.onContactPress(item)} &gt;
          &lt;Image style={styles.rightArrow}
            source={require('../../images/right_arrow.png')}/&gt; 
        &lt;/TouchableOpacity&gt;
      &lt;/View&gt;
     )  
  }
  </code></pre>
  
  <p>and the the error is </p>
  
  <pre><code>undefined is not an object (evaluating '_this3.onContactPress()')
  </code></pre>
  
  <p>What I'm doing wrong here? Is there a way to pass the contact details of the selected person to the next screen? Please help me out.</p>