React-Native : measure a View

Question

I\'m trying to measure a view using a ref, but the width returned is 0 despite the fact that I see the view displayed on the screen (and it\'s far

Answer 1

To measure view size, no need to use ref at all. You can get it from nativeEvent passed by onLayout.

measureView(event: Object) {
   console.log(`*** event: ${JSON.stringify(event.nativeEvent)}`);
   // you'll get something like this here:
   // {"target":1105,"layout":{"y":0,"width":256,"x":32,"height":54.5}}
}

render() {
    return (
        <View onLayout={(event) => {this.measureView(event)}} />
    );
}

Answer 2

You want to measure the progress bar onLayout.

var Time = React.createClass({
  getInitialState: function() {
    return({ progressMaxSize: 0 }); 
  },
  measureProgressBar: function() {
    this.progressBar.measure(this.setWidthProgressMaxSize);
  },
  setWidthProgressMaxSize: function(ox, oy, width, height, px, py) {
    this.setState({ progressMaxSize: width });
  },
  render: function() {
    return(
      <View style={listViewStyle.time} ref={(c) => { this.progressBar = c; } onLayout={this.measureProgressBar}>
        <View style={listViewStyle.progressBar} >
          <View style={[listViewStyle.progressMax, { width: this.state.progressMaxSize }]}/>
        </View>
      </View>
    );
  }
});

Answer 3

During the night some guys talked about a (hacky) solution but it solved my problem, found it here: https://github.com/facebook/react-native/issues/953

Basically the solution is to use setTimeout and everything just works magically:

componentDidMount: function() {
  setTimeout(this.measureProgressBar);
},

measureProgressBar: function() {
  this.refs.progressBar.measure((a, b, width, height, px, py) =>
    this.setState({ progressMaxSize: width })
  );
}