问题

Map类组件处理位置对象作为参数
```javascript
export default class Map extends React.Component {
  render() {
    const location = this.props.route.params;
    console.log("Map location is: ", JSON.stringify(location));
    return (
      <View style={{ flex: 1 }}>
        <MapView style={{ flex: 1 }} region={region}></MapView>
      </View>
    );
  }
}
const region = {
  latitude: 35.6762,
  longitude: 139.6503,
  latitudeDelta: 0.1,
  longitudeDelta: 0.1,
};

仪表板功能通过导航将位置对象传递给Map类

export default function Dashboard({ navigation }) {
  const [location, setLocation] = useState(false);

  const onGetLocation = async () => {
    const result = requestLocationPermission();
    console.log("Request location permission response: ", result);
    await result.then((res) => {
      console.log("res is:", res);
      if (res) {
        Geolocation.getCurrentPosition(
          async (position) => {
            setLocation(position);
          },
          async (error) => {
            // 查看下面的错误代码表。
            console.log(error.code, error.message);
            setLocation(false);
          },
          { enableHighAccuracy: true, timeout: 15000, maximumAge: 10000 }
        );
      }
    });
    navigation.navigate("Map", location); //位置始终为false？？
  };

  return (
    // ...
    // ...
    // ...
  );
}

为什么位置总是设置为false，即使它被设置为当前位置。
我是React Native的新手。我是不是错误地使用了async/await？任何形式的帮助或指导都将不胜感激。

<details>
<summary>英文:</summary>

Map class component handles location object as params

export default class Map extends React.Component {
render() {
const location = this.props.route.params;
console.log("Map location is: ", JSON.stringify(location));
return (
<View style={{ flex: 1 }}>
<MapView style={{ flex: 1 }} region={region}></MapView>
</View>
);
}
}
const region = {
latitude: 35.6762,
longitude: 139.6503,
latitudeDelta: 0.1,
longitudeDelta: 0.1,
};

Dashboard function passes location object to Map class using navigation

export default function Dashboard({ navigation }) {
const [location, setLocation] = useState(false);

const onGetLocation = async () => {
const result = requestLocationPermission();
console.log("Request location permission response: ", result);
await result.then((res) => {
console.log("res is:", res);
if (res) {
Geolocation.getCurrentPosition(
async (position) => {
setLocation(position);
},
async (error) => {
// See error code charts below.
console.log(error.code, error.message);
setLocation(false);
},
{ enableHighAccuracy: true, timeout: 15000, maximumAge: 10000 }
);
}
});
navigation.navigate("Map", location); //location is always false??
};

return (
...
...
...

Why does location always sets to false even though it's set to current location. 
I'm new to react native. Am i incorrectly using aync/await? Any kind of help or guidance is appreciated.

</details>


# 答案1
**得分**: 1

>为什么位置总是设置为false，即使它被设置为当前位置。

实际上它并不是被设置为`false`，而是因为在创建时它最初是`false`，这里导航发生在Promise到达之前，所以这样。

你想要在`.then`块内发生导航，因此你不需要使用状态，只需直接使用`position`或`false`：

```js
if (res) {
    Geolocation.getCurrentPosition(
      async (position) => {
        setLocation(position); // 你可能不需要更新状态，或者根本不需要它
        navigation.navigate("Map", position); // 在这里不能使用"location"，因为它还没有更新
      },
      async (error) => {
        // 请参考下面的错误代码表。
        console.log(error.code, error.message);
        setLocation(false); // 你可能不需要更新状态，或者根本不需要它
        navigation.navigate("Map", false); // 在这里不能使用"location"，因为它还没有更新
      },
      { enableHighAccuracy: true, timeout: 15000, maximumAge: 10000 }
    );
  } else {
    // ... 处理else情况
  }

如果需要进一步的帮助，请告诉我。

if (res) {
    Geolocation.getCurrentPosition(
      async (position) => {
        setLocation(position); // you may don't need to update the state or maybe don't need it at all
        navigation.navigate("Map", position); // you cannot use "location" here because it isn't updated yet
      },
      async (error) => {
        // See error code charts below.
        console.log(error.code, error.message);
        setLocation(false); // you may don't need to update the state or maybe don't need it at all
        navigation.navigate("Map", false); //you cannot use "location" here because it isn't updated yet
      },
      { enableHighAccuracy: true, timeout: 15000, maximumAge: 10000 }
    );
  } else {
    // ... hanlde the else case
  }