How do I find out the x,y position of where an element is positioned on the screen, I'm using React Native v0.14. I have tried the following but it says measure is not a function.

```
componentDidMount() {
    setTimeout(this.measurePosition);
  },
measurePosition() {
    this.refs.q.measure((a, b, width, height, px,py ) => console.log(width))
},

```