react-google-maps将地图缩放为圆形

Question

This is mainly a question about 'translating' JS to JSX.

I have a react-google-maps map which contains a marker, and a circle around that marker:

The Map component:

export class Map extends Component {
  render() {
    const GoogleMapInstance = withGoogleMap(props => (
      <GoogleMap
        defaultCenter = { { lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) } }
        defaultZoom = { 16 }
        defaultOptions={{ styles: mapStyles }}
      >
        <Marker position={{ lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) }}/>
        <Circle center={{ lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) }} radius={parseFloat(this.props.accuracy)} options={{ fillColor: 'red', strokeColor: 'red' }}/>
      </GoogleMap>
    ))
    return (
      <div>
        <GoogleMapInstance
          containerElement={ <div style={{ height: '600px', width: '100%' }}/> }
          mapElement={ <div style={{ height: '100%' }}/> }
        />
      </div>
    )
  }
}

I would like the map to be zoomed such that the circle takes up about 50% of the map. I understand using the Javascript API, I can just do:

map.fitBounds(circle.getBounds())

But I'm not sure how to integrate that with the JSX that I have...

Answer 1

You probably want to do something like this:

export class Map extends Component {
  constructor(props) {
    super(props)
    this.map = React.createRef()
    this.circle = React.createRef()
  }

  componentDidMount() {
    if (this.map && this.circle) {
      const bounds = this.circle.current.getBounds()
      this.map.current.fitBounds(bounds)
    }
  }

  render() {
    const GoogleMapInstance = withGoogleMap(props => (
      <GoogleMap
        defaultCenter = { { lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) } }
        defaultZoom = { 16 }
        defaultOptions={{ styles: mapStyles }}
        ref={this.map}
      >
        <Marker position={{ lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) }}/>
        <Circle ref={this.circle} center={{ lat: parseFloat(this.props.lat), lng: parseFloat(this.props.lng) }} radius={parseFloat(this.props.accuracy)} options={{ fillColor: 'red', strokeColor: 'red' }}/>
      </GoogleMap>
    ))
    return (
      <div>
        <GoogleMapInstance
          containerElement={ <div style={{ height: '600px', width: '100%' }}/> }
          mapElement={ <div style={{ height: '100%' }}/> }
        />
      </div>
    )
  }
}

The refs create a way to access the GoogleMap and Circle nodes, and the componentDidMount is a lifecycle hook that lets you run the fitBounds call when the Map component is first rendered to the DOM.

Answer 2

Indeed, you could access native Google Map and Circle objects via Ref and manipulate it. But when it comes to getting map instance, prefer Map idle event over componentDidMount() lifecycle method to guarantee the map is ready, for example:

handleMapIdle() {
   const map = this.map.current; //get Google Map instance
   //...
}

where

 <GoogleMap
        ref={this.map}
        onIdle={this.handleMapIdle}
        ...
      >
      ...
 </GoogleMap>

Here is a modified Map component:

class Map extends Component {
  constructor(props) {
    super(props);
    this.map = React.createRef();
    this.circle = React.createRef();
    this.handleMapIdle = this.handleMapIdle.bind(this);
    this.idleCalled = false;
  }

  handleMapIdle() {
    if (!this.idleCalled) {
      const bounds = this.circle.current.getBounds();
      this.map.current.fitBounds(bounds);
      this.idleCalled = true;
    }
  }

  render() {
    const GoogleMapInstance = withGoogleMap(props => (
      <GoogleMap
        ref={this.map}
        defaultCenter={{
          lat: parseFloat(this.props.lat),
          lng: parseFloat(this.props.lng)
        }}
        defaultZoom={this.props.zoom}
        onIdle={this.handleMapIdle}
      >
        <Marker
          position={{
            lat: parseFloat(this.props.lat),
            lng: parseFloat(this.props.lng)
          }}
        />
        <Circle
          ref={this.circle}
          center={{
            lat: parseFloat(this.props.lat),
            lng: parseFloat(this.props.lng)
          }}
          radius={parseFloat(this.props.accuracy)}
          options={{ fillColor: "red", strokeColor: "red" }}
        />
      </GoogleMap>
    ));
    return (
      <div>
        <GoogleMapInstance
          containerElement={<div style={{ height: "600px", width: "100%" }} />}
          mapElement={<div style={{ height: "100%" }} />}
        />
      </div>
    );
  }
}

Demo