React-Native Image Height (Full Width)

Question

I have an image that I pull down from a url. I do not know the dimensions of this image ahead of time.

How do I style / layout the <Image/> so it is the full width of the parent view and the height is calculated so that the aspect ratio is maintained?

I have tried using onLoad in 0.34.0-rc.0 and the height / width are both 0 in event.nativeEvent.source.

The image is in a <ScrollView/>. I am not after a full screen image.

Answer 1

My use was very similar in that I needed to display an image with full screen width but maintaining its aspect ratio.

Based on @JasonGaare's answer to use Image.getSize(), I came up with the following implementation:

class PostItem extends React.Component {

  state = {
    imgWidth: 0,
    imgHeight: 0,
  }

  componentDidMount() {

    Image.getSize(this.props.imageUrl, (width, height) => {
      // calculate image width and height 
      const screenWidth = Dimensions.get('window').width
      const scaleFactor = width / screenWidth
      const imageHeight = height / scaleFactor
      this.setState({imgWidth: screenWidth, imgHeight: imageHeight})
    })
  }

  render() {

    const {imgWidth, imgHeight} = this.state

    return (
      <View>
        <Image
          style={{width: imgWidth, height: imgHeight}}
          source={{uri: this.props.imageUrl}}
        />
        <Text style={styles.title}>
          {this.props.description}
        </Text>
      </View>
    )
  }
}