javascript - 在 React 中设置标记超时
问题描述
此 Marker 组件渲染中的动画道具使用标记的数组获取一个标记，如果有一个则反弹，如果有多个则丢弃：
<Marker
key={index}
position={{lat: marker.lat, lng: marker.lng}}
onClick={() => props.handleMarkerClick(marker)}
animation={array.length === 1 ? google.maps.Animation.BOUNCE : google.maps.Animation.DROP}
>
但是，我的目标是为反弹设置 750 毫秒超时（基于对另一个 SO 问题的回答）。我不能用条件三元运算符做到这一点，所以我做了两次尝试为此创建一个函数，将 Marker 组件中的动画属性替换为animation={array.length === 1 ? bounceMarker() : google.maps.Animation.DROP}and 都有问题。
我认为这个可以工作，但使用google.maps.Animation.BOUNCE;会引发 ESLint 错误“预期分配或函数调用，而是看到一个表达式。”
const bounceMarker = () => {
google.maps.Animation.BOUNCE;
setTimeout(() => {
marker.setAnimation(null);
}, 750);
};
此函数基于谷歌的标记教程，并导致错误“marker.getAnimation is not a function”：
const bounceMarker = () => {
if (marker.getAnimation() !== null) {
marker.setAnimation(null);
} else {
marker.setAnimation(google.maps.Animation.BOUNCE);
setTimeout(() => {
marker.setAnimation(null);
}, 750);
}
};
如果有用的话，这里是我从这个文件中获得的完整代码，其中两个函数被注释掉了：
// Specifies global variable to ESLint (bundled with create-react-app), circumventing no-undef rule. See https://eslint.org/docs/user-guide/configuring#specifying-globals
/* global google */
// This component's code is from react-google-maps implementation instructions https://tomchentw.github.io/react-google-maps/#installation
import React, { Component , Fragment } from 'react';
import { withScriptjs , withGoogleMap, GoogleMap, Marker, InfoWindow } from 'react-google-maps';
const MyMapComponent = withScriptjs(
withGoogleMap(props => (
<GoogleMap
zoom={props.zoom}
defaultCenter={{ lat: 47.6093, lng: -122.3309 }}
>
{/* If there are markers, filters all visible markers (creating new array) then maps over newly created array taking the marker and marker's array index as arguments, rendering each Marker component with the marker index set as the key and the marker's lat and long as the position */}
{props.markers &&
props.markers.filter(marker => marker.isVisible)
// "Keys help React identify which items have changed, are added, or are removed. Keys should be given to the elements inside the array to give the elements a stable identity ... When you don’t have stable IDs for rendered items, you may use the item index as a key as a last resort" https://reactjs.org/docs/lists-and-keys.html
.map((marker, index, array) => {
// const bounceMarker = () => {
// if (marker.getAnimation() !== null) {
// marker.setAnimation(null);
// } else {
// marker.setAnimation(google.maps.Animation.BOUNCE);
// setTimeout(() => {
// marker.setAnimation(null);
// }, 750);
// }
// };
// const bounceMarker = () => {
// google.maps.Animation.BOUNCE;
// setTimeout(() => {
// marker.setAnimation(null);
// }, 750);
// };
const venueInfo = props.venues.find(venue => venue.id === marker.id);
return (
<Marker
key={index}
position={{lat: marker.lat, lng: marker.lng}}
// Marker click event listener, defined in App component class
onClick={() => props.handleMarkerClick(marker)}
animation={array.length === 1 ? bounceMarker() : google.maps.Animation.DROP}
>
{/* Show marker's InfoWindow when its isOpen state is set to true (set in app.js) */}
{marker.isOpen &&
<InfoWindow>
{/* If a venueInfo is not falsey and: 1) if there's a name and bestPhoto property, return the venue photo and name; 2) if there's only a name property, display the name only; 3) if there's only a photo property, display the photo only. If neither are available and/or venueInfo is falsy display text indicating no info available. See SO question about multiple ternary operators https://stackoverflow.com/questions/7757549/multiple-ternary-operators */}
{venueInfo && venueInfo.name && venueInfo.bestPhoto ?
<Fragment>
<p>{venueInfo.name}</p>
<img src={`${venueInfo.bestPhoto.prefix}200x200${venueInfo.bestPhoto.suffix}`}
// Screen readers already announce as image; don't need the word "image", "photo", etc.
alt={"Venue"}
/>
</Fragment> : venueInfo && venueInfo.name ? <p>{venueInfo.name}</p> : venueInfo && venueInfo.bestPhoto ? <img src={`${venueInfo.bestPhoto.prefix}200x200${venueInfo.bestPhoto.suffix}`}
// Screen readers already announce as image; don't need the word "image", "photo", etc.
alt={"Venue"}
/> : <p>No info available</p>}
</InfoWindow>
}
</Marker>
);
})}
</GoogleMap>
))
);
export default class Map extends Component {
render() {
return (
<MyMapComponent
// This is making the this.setState passed into Map component (as its prop) inside App's component class's render method available to MyMapComponent, which is how props from this.setState are eventually included inside MyMapComponent class (such as zoom={props.zoom})
{...this.props}
isMarkerShown
googleMapURL="https://maps.googleapis.com/maps/api/js?v=3.exp&key=AIzaSyDjl8LxY7Edfulq6t_VDaQsYY4ymPjwN0w"
// CSS declarations are placed in double curly braces because attributes accept JS objects; this is how to include an object literal. See https://stackoverflow.com/questions/22671582/what-is-the-purpose-of-double-curly-braces-in-reacts-jsx-syntax
loadingElement={<div style={{ height: `100%` }} />}
containerElement={<div style={{ height: `100%`, width: `75%` }} />}
mapElement={<div style={{ height: `100%` }} />}
/>
);
}
}
解决方案
您收到此错误
marker.getAnimation 不是函数
因为marker不是实际google.maps.Marker对象。
与其渲染标记并随后更新属性，不如使用超时渲染标记（基本上与使用 setTimeout() 的标记动画Marker.animation示例中演示的方式相同）？
为此，建议引入一种状态来保持动画标记
class MarkersAnimation extends React.Component {
constructor(props) {
super(props);
this.state = {
markers: []
};
}
render() {
return (
<GoogleMap
defaultZoom={this.props.zoom}
defaultCenter={this.props.center}
>
{this.state.markers.map((place, i) => {
return (
<Marker
animation={google.maps.Animation.BOUNCE}
id={place.id}
key={place.id}
position={{ lat: place.lat, lng: place.lng }}
/>
);
})}
</GoogleMap>
);
}
componentDidMount() {
const { markers, delay } = this.props;
this.interval = setInterval(() => {
this.setState(prev => ({
markers: prev.markers.concat([markers.shift()])
}));
if (!markers.length) clearInterval(this.interval);
}, delay);
}
componentWillUnmount() {
clearInterval(this.interval);
}
}