React Native: Getting the position of an element

Question

I am styling an Image component with flexbox to be in the center of the screen which works pretty well. Now I want a second Image component to be d

Answer 1

React Native provides a .measure(...) method which takes a callback and calls it with the offsets and width/height of a component:

myComponent.measure( (fx, fy, width, height, px, py) => {

    console.log('Component width is: ' + width)
    console.log('Component height is: ' + height)
    console.log('X offset to frame: ' + fx)
    console.log('Y offset to frame: ' + fy)
    console.log('X offset to page: ' + px)
    console.log('Y offset to page: ' + py)
})

Example...

The following calculates the layout of a custom component after it is rendered:

class MyComponent extends React.Component {
    render() {
        return  { this.myComponent = view; }} />
    }
    componentDidMount() {
        // Print component dimensions to console
        this.myComponent.measure( (fx, fy, width, height, px, py) => {
            console.log('Component width is: ' + width)
            console.log('Component height is: ' + height)
            console.log('X offset to frame: ' + fx)
            console.log('Y offset to frame: ' + fy)
            console.log('X offset to page: ' + px)
            console.log('Y offset to page: ' + py)
        })        
    }
}

---

Bug notes

• Note that sometimes the component does not finish rendering before componentDidMount() is called. If you are getting zeros as a result from measure(...), then wrapping it in a setTimeout should solve the problem, i.e.:

  setTimeout( myComponent.measure(...), 0 )