UI 不会在状态更改时更新 [英] UI does not update on state change

问题描述

我正在使用 react native maps 并在 componentDidMount() 上要求用户启用他们的位置.

I am using react native maps and on componentDidMount() asking user to enable their location.

componentDidMount() {
if (Platform.OS === 'android') {
  RNAndroidLocationEnabler.promptForEnableLocationIfNeeded({ interval: 20000, fastInterval: 5000 })
    .then(data => {
      console.log(data);

      this.findingLocation();
    }).catch(err => {
    });
}
else if (Platform.OS === 'ios') {
  this.findingLocation();
}

}

在 findingLocation() 中，我试图像这样获取用户的当前位置

And in findingLocation() I am trying to get the current location of user like this

 findingLocation = () => {
Geolocation.getCurrentPosition(
  position => {
    this.setState({
      region: {
        latitude: position.coords.latitude,
        longitude: position.coords.longitude,
        latitudeDelta: 0.0043,
        longitudeDelta: 0.0034,
      }
    }, () => {
      console.warn(this.state.region);
    });
  },
  error => console.warn('Error', JSON.stringify(error)),
  { enableHighAccuracy: true, timeout: 20000, maximumAge: 10000 },
);

}

在控制台中，我得到了当前位置的纬度.但有时它不会反映在 UI 上.

And in console I am getting lat long of current location. But it does not reflect on UI sometimes .

界面代码

<MapView
      provider={PROVIDER_GOOGLE}
      style={styles.map}
      region={this.state.region}
      onRegionChangeComplete={this.onRegionChange}
      zoomEnabled={true}
      showsUserLocation={true}
      zoomControlEnabled={true}
      showsMyLocationButton={true}
    />

我使用的库是 https://github.com/react-用于 MAP & 的 native-community/react-native-mapshttps://www.npmjs.com/package/@react-native-GEOLOCATION 的社区/地理位置.

请帮帮我.我哪里出错了.提前致谢.

Help me please. Where I am going wrong. Thanks in advance.

推荐答案

在 setState 函数中使用展开运算符.至于为什么，请阅读这篇文章:https://medium.com/pro-react/a-brief-talk-about-immutability-and-react-s-helpers-70919ab8ae7c

Use the spread operator in your setState function. As for why, read this article: https://medium.com/pro-react/a-brief-talk-about-immutability-and-react-s-helpers-70919ab8ae7c

this.setState(prevState => ({
  region: {
    ...prevState.region
    latitude: position.coords.latitude,
    longitude: position.coords.longitude,
    latitudeDelta: 0.0043,
    longitudeDelta: 0.0034,
  }
}), () => {
  console.warn(this.state.region);
})

这篇关于UI 不会在状态更改时更新的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！