title: Why PermissionAndroid doesn't work?
body: <p>I get this error:</p>
  
  <blockquote>
    <p>Reference Error: can't find variable PermissionsAndroid</p>
  </blockquote>
  
  <p>This is my code:</p>
  
  <p>AndroidManifest.xml:</p>
  
  <pre><code>&lt;uses-permission android:name="android.permission.CAMERA" /&gt;
  </code></pre>
  
  <p>index.android.js:</p>
  
  <pre><code>constructor(props) {
    super(props);
    this.state = {
      message: 'Hi world'
    };
    this.requestCameraPermission();
  }
  
  
  async requestCameraPermission() {
    try {
      const granted = await PermissionsAndroid.requestPermission(
        PermissionsAndroid.PERMISSIONS.CAMERA,
        {
          'title': 'Cool Photo App Camera Permission',
          'message': 'Cool Photo App needs access to your camera ' +
                     'so you can take awesome pictures.'
        }
      )
      if (granted === PermissionsAndroid.RESULTS.GRANTED) {
        console.log("You can use the camera")
      } else {
        console.log("Camera permission denied")
      }
    } catch (err) {
      console.warn(err)
    }
  }
  </code></pre>