我已经在我的页面上实现了Google Maps API，它非常好地工作，除了当我刷新屏幕时。
一旦我点击刷新，我就会得到这种类型的错误：
Cannot read property of maps, undefined
具体来说，它发生在Map类的第28行附近。
这是我为我的API设置脚本的地方，当我检查页面时，我可以看到它是存在的(即使当我刷新页面时(：
class App extends Component {
// Render a script tag for scriptUrl in head of the HTML page
addScriptToPage(scriptUrl) {
const script = document.createElement("script");
script.src = scriptUrl;
document.head.appendChild(script);
}
componentDidMount() {
// CreateReactApp requires the REACT_APP_ prefix for env vars
let MAPS_API_KEY = process.env.REACT_APP_MAPS_API_KEY;
// place the google maps api as a script tag in the head
// this script places a google object on window.google
let mapsApiUrl = `https://maps.googleapis.com/maps/api/js?key=${MAPS_API_KEY}`;
this.addScriptToPage(mapsApiUrl);
}
render() {
return (
<div className='app-wrapper'>
<Modal />
<NavBarContainer />
<div className="app-main-content-wrapper">
<Switch>
<Route exact path='/' component={SpotIndex} />
<Route exact path='/spots/:spotId' component={SpotDetail} />
<Route exact path='/search/:find_loc' component={SearchContainer} />
</Switch>
</div>
</div>
);
}
};
这是我的地图类：
class Map extends Component {
constructor(props) {
super(props);
}
// Initially mounts the map with first search input
componentDidMount() {
this.drawMap(this.props.find_loc);
}
componentWillReceiveProps(newProps) {
this.drawMap(newProps.find_loc);
}
drawMap(address) {
// Solves problem of linting rule in ReactJS that forbids unknown global vars
const google = window.google;
const map = document.getElementById('map-container');
// Creating the map
MapUtil.setOptionsFromLocation(address)
.then(options => {
this.map = new google.maps.Map(map, options);
// before adding markers, set up bounds
let bounds = new google.maps.LatLngBounds();
// Displaying nearby spots
this.props.spots.forEach(spot => {
// Create a position from spot coordinates
const latitude = spot.latitude;
const longitude = spot.longitude;
const position = new google.maps.LatLng(latitude, longitude);
// Place markers on the map
const marker = new google.maps.Marker({
position,
map: this.map
});
// extend the bounds to fit this position
bounds.extend(position);
});
// Autozooming and autocentering if there are results
if (this.props.spots.length) {
// Autozooming
this.map.fitBounds(bounds);
// Adjust zooming value if too large
let theMap = this.map;
var listener = google.maps.event.addListener(theMap, "idle", function () {
if (theMap.getZoom() > 16) theMap.setZoom(16);
google.maps.event.removeListener(listener);
});
// Autocentering
this.map.panToBounds(bounds);
}
});
}
// Renders Map component
render() {
return <div id="map-container"></div>;
}
}
根据下面的建议，以上组件中的错误似乎是而不是。经过一些挖掘，我确实找到了另一个我称之为Map组件的地方。
这是一个通用搜索组件，用于呈现Map和SearchIndex(搜索结果(：
class Search extends React.Component {
constructor(props) {
super(props);
this.state = { find_loc: this.props.find_loc };
}
// Triggers a re-render when component receives new props
componentWillReceiveProps(newProps) {
this.setState({ find_loc: newProps.match.params.find_loc });
}
// Gets spots matching search input
getSpots(spots) {
// Library of state abbreviations
const states = {
"AL": "alabama",
"AK": "alaska",
"AS": "american samoa",
"AZ": "arizona",
"AR": "arkansas",
"CA": "california",
"CO": "colorado",
"CT": "connecticut",
"DE": "delaware",
"DC": "district of columbia",
"FL": "florida",
"GA": "georgia",
"GU": "guam",
"HI": "hawaii",
"ID": "idaho",
"IL": "illinois",
"IN": "indiana",
"IA": "iowa",
"KS": "kansas",
"KY": "kentucky",
"LA": "louisiana",
"ME": "maine",
"MD": "maryland",
"MA": "massachusetts",
"MI": "michigan",
"MN": "minnesota",
"MS": "mississippi",
"MO": "missouri",
"MT": "montana",
"NE": "nebraska",
"NV": "nevada",
"NH": "new hampshire",
"NJ": "new jersey",
"NM": "new mexico",
"NY": "new york",
"NC": "north carolina",
"ND": "north dakota",
"OH": "ohio",
"OK": "oklahoma",
"OR": "oregon",
"PA": "pennsylvania",
"PR": "puerto rico",
"RI": "rhode island",
"SC": "south carolina",
"SD": "south dakota",
"TN": "tennessee",
"TX": "texas",
"UT": "utah",
"VT": "vermont",
"VI": "virgin Islands",
"VA": "virginia",
"WA": "washington",
"WV": "west Virginia",
"WI": "wisconsin",
"WY": "wyoming"
}
// Getting lowercased location string from search input
const location = this.state.find_loc;
let locationArr;
let lowercasedLocation = [];
let foundSpots = [];
if (location) {
locationArr = location.split(' ');
locationArr.forEach(word => lowercasedLocation.push(word.toLowerCase()));
lowercasedLocation = lowercasedLocation.join(' ');
}
// Searching for spots matching location
spots.forEach(spot => {
const city = spot.city.toLowerCase();
const stateAbbr = spot.state.toLowerCase();
const stateFull = states[spot.state];
if (city === lowercasedLocation || stateAbbr === lowercasedLocation || stateFull === lowercasedLocation) {
foundSpots.push(spot);
}
});
return foundSpots;
}
// Renders Search component
render() {
const { spots } = this.props;
const foundSpots = this.getSpots(spots);
return (
<div className="search-container">
<div className="search-results-wrapper">
<SearchIndex spots={foundSpots} find_loc={this.state.find_loc} fetchSpots={this.props.fetchSpots} />
<Map spots={foundSpots} find_loc={this.state.find_loc} />
</div>
<Footer />
</div>
);
}
}
我之前在SearchIndex中遇到过类似的加载问题，因为在重新加载页面时spots没有被提取。但我通过明确地告诉SearchIndex组件在安装组件时获取所有点来解决这个问题；我想，对于Map(特别是window.google(来说，这可能是一个类似的问题？
为tilesloaded事件添加侦听器：
this.map = new google.maps.Map(map, options);
this.map.addListener('tilesloaded', function () {
...