反应本机说,当它显然是对象时,不确定的不是对象!我对发生的事情感到困惑。
查看以下代码。浏览到render()
功能。请参阅以下... console.log(cords.coords);
console.log(cords.coords);
输出以下...
08:37:22: Object {
08:37:22: "coords": Object {
08:37:22: "accuracy": 5,
08:37:22: "altitude": 0,
08:37:22: "altitudeAccuracy": -1,
08:37:22: "heading": -1,
08:37:22: "latitude": 39.946313,
08:37:22: "longitude": -82.810829,
08:37:22: "speed": -1,
08:37:22: },
08:37:22: "timestamp": 1522413346644.865,
08:37:22: }
一个人会说要检索这些数据,您必须执行以下操作。console.log(cords.coords.coords.latitude)
获得纬度。但是它说它不确定。它说即使我做console.log(cords.coords.coords)
,它也没有定义?我在做什么错?
注意console.log(cords.coords);
是脚本中触发错误的地方
请记住,以下代码确实有效。只有当我将console.log(cords.coords);
更改为console.log(cords.coords.coords.latitude);
时,它会破坏
import React, { Component } from 'react';
import {Platform, StyleSheet, Dimensions, Text, View } from 'react-native';
import MapView, { PROVIDER_GOOGLE } from 'react-native-maps';
import { Constants, Location, Permissions } from 'expo';
export default class MapScreen extends Component<Props> {
constructor(props) {
super(props);
this.state = {
markers: [{
title: 'hello',
coordinates: {
latitude: 39.946313,
longitude: -82.810829
},
},
{
title: 'hello',
coordinates: {
latitude: 39.945838,
longitude: -82.813018
},
}
]
}
console.log("Get Geo Synce");
this._getLocationAsync();
}
_getLocationAsync = async () => {
console.log("load geo sync");
//Location.setApiKey("AIzaSyBY45685CkDPy5a4ss29IL2ZjIvTvYTMyk");
let { status } = await Permissions.askAsync(Permissions.LOCATION);
if (status !== 'granted') {
this.setState({
locationResult: 'Permission to access location was denied',
});
}
console.log("Loading Location 1");
let location = await Expo.Location.getCurrentPositionAsync({ enableHighAccuracy: true });
console.log("Retrieved Location");
this.setState({ coords: location });
};
render() {
const { params } = this.props.navigation.state;
let coords = params ? params.coords.coords : null;
let cords = this.state;
console.log(cords.coords);
//let coords = state.locationResult.coords;
return (
<View style={{flex: 1}}>
<MapView
style={ styles.container }
initialRegion={{
latitude:coords.latitude,
longitude:coords.longitude,
latitudeDelta:0.0992,
longitudeDelta:0.0421,
}}
>
{this.state.markers.map(marker => (
<MapView.Marker
coordinate={marker.coordinates}
title={marker.title}
/>
))}
</MapView>
</View>
);
}
}
const styles = StyleSheet.create({
container: {
width:'100%',
height:'100%',
},
});
最好在组件安装在componentdidmount生命周期方法中,而代码的问题是,初始渲染this.state.coords.coords是未定义的,一旦API请求,则进行了问题。解决此问题。STATE通过this.setState方法进行更新,并定义了this.state.coords。因此,为了使它工作,请尝试一下,
return this.state.coords instanceof Object ? (
<View style={{flex: 1}}>
<MapView
style={ styles.container }
initialRegion={{
latitude:coords.latitude,
longitude:coords.longitude,
latitudeDelta:0.0992,
longitudeDelta:0.0421,
}}
>
{this.state.markers.map(marker => (
<MapView.Marker
coordinate={marker.coordinates}
title={marker.title}
/>
))}
</MapView>
</View>
) : <Text>Fetching, Please wait....</Text>;