ReactJS - get latitude on click and show it in input

问题

Beginner here. I have a button that gets latitude and longitude using the geolocation API. I get the location fine on my console, but I'm having trouble showing them in a input box (so that I can then post the location information later). Below is my code for the component:

export class GetLocation extends Component{
constructor(){
    super();
    this.state = {
        latitude: '',
        longitude: ''
    };
    this.getMyLocation = this.getMyLocation.bind(this);

}

ComponentDidMount(){
    this.getMyLocation();
}
getMyLocation = (e) => {
let location = null;
let latitude = null;
let longitude = null;
if (window.navigator && window.navigator.geolocation) {
    location = window.navigator.geolocation
}
if (location){
    location.getCurrentPosition(function (position) {
        latitude = position.coords.latitude;
        longitude= position.coords.longitude;
        console.log(latitude);
        console.log(longitude);
    })
}
    this.setState({latitude: latitude, longitude: longitude})

}

render(){
    return(
    <div>
        <p>Your location is </p>
        <Field name="latitude" component="input" onChange={this.getMyLocation}/>
        <button type="button" onClick={this.getMyLocation}>Get Geolocation</button>
    </div>

    );
}
}

I'm using redux-form and this component is a part of a wizard form (in case you were wondering about the Field Component)

回答1:

ComponentDidMount should be componentDidMount. I believe you have to set a value prop to your Field right?

Also, as @bennygenel mentioned, you don't need to bind getMyLocation in the constructor since you are already using arrow function (I did on my example, feel free to change it). In order to have access to this.state inside getCurrentPosition's callback, you either need to bind the success callback or make use of arrow function.

class App extends React.Component {
  constructor() {
    super()

    this.state = {
      latitude: '',
      longitude: '',
    }

    this.getMyLocation = this.getMyLocation.bind(this)
  }
  
  componentDidMount() {
    this.getMyLocation()
  }

  getMyLocation() {
    const location = window.navigator && window.navigator.geolocation
    
    if (location) {
      location.getCurrentPosition((position) => {
        this.setState({
          latitude: position.coords.latitude,
          longitude: position.coords.longitude,
        })
      }, (error) => {
        this.setState({ latitude: 'err-latitude', longitude: 'err-longitude' })
      })
    }

  }

  render() {
    const { latitude, longitude } = this.state
    
    return (
      <div>
        <input type="text" value={latitude} />
        <input type="text" value={longitude} />
      </div>
    )
  }
}

ReactDOM.render(
  <App />,
  document.getElementById('root')
)

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>

<div id="root"></div>

回答2:

Like the other answers say you need to pass longitude and latitude values to the input so you can be able to show but there is another problem. You are not setting the longitude and latitude in the right place.

if (location){
    location.getCurrentPosition(function (position) {
        latitude = position.coords.latitude;
        longitude= position.coords.longitude;
        console.log(latitude);
        console.log(longitude);
        this.setState({
           latitude: latitude, 
           longitude: longitude
        }); // you should set state when you have the values.
    }.bind(this)); // you need to bind this so you can use setState
}

来源：https://stackoverflow.com/questions/46387375/reactjs-get-latitude-on-click-and-show-it-in-input

标签

javascript

reactjs

redux-form