react-native - 如何在 react-native-map 中放大/缩小？

Question

我正在使用 react-native 来构建地图应用程序。我正在使用的 api 来自此链接：https ://github.com/lelandrichardson/react-native-maps 。以下是我将地图带到我的应用程序的代码。我徘徊如何在该地图上给出缩放值。以及当用户单击地图上的按钮时如何更改缩放值。我应该使用什么缩放 API 来实现这一点？

import React, {


AppRegistry,
  Component,
  StyleSheet,
  Text,
  View,
  Image,
  ListView,
  TextInput,
  TouchableHighlight,
  Dimensions,
 //MapView,
} from 'react-native';

import MapView from 'react-native-maps';

const styles = StyleSheet.create({
  map: {
    position: 'absolute',
    top: 0,
    left: 0,
    right: 0,
    bottom: 0,
  },
  container: {
    flexDirection: 'row',
    justifyContent: 'space-between',
    padding: 30,
    flex: 1,
    alignItems: 'center'
  },
  inputText: {
    height: 36,
      padding: 4,
      marginRight: 5,
      flex: 4,
      fontSize: 18,
      borderWidth: 1,
      borderColor: '#48BBEC',
      borderRadius: 8,
      color: '#48BBEC'
  }
});

class MapPage extends Component{

    constructor(props){
        super(props);
        this.state = {
            region:{
                latitude: 4.21048,
                longitude: 101.97577,
            latitudeDelta: 10,
            longitudeDelta: 5
            }
        }
    }

    render() {
        return(
            <View style={styles.container}>
                <TextInput style={styles.inputText}></TextInput>
                <MapView 
                    style={ styles.map }
                    mapType={"standard"}
                    region={this.state.region}
                    zoomEnabled={true}
                    scrollEnabled={true}
                    showsScale={true}
                  ></MapView>
            </View>
            )
    }
}

module.exports = MapPage;

Answer 1

您应该使用该animateToRegion方法（请参见此处）

它需要一个具有latitudeDelta和的区域对象longitudeDelta。使用这些设置缩放级别。

更新：

在一个Region对象中latitude，longitude指定中心位置，latitudeDelta并longitudeDelta指定可视地图区域的跨度。

此博客文章 中的这张图片很好地说明了这一点（LatΔ 和 LngΔ）。

Answer 2

我能够使用Dimensions.get('window');

            const window = Dimensions.get('window');
            const { width, height }  = window
            LONGITUDE_DELTA = LATITUD_DELTA + (width / height)

并且默认设置为LATITUD_DELTA = 0.0922. 然后只需使用中的道具更新此onRegionChangeComplete值<MapView>

Answer 3

新的 React Native Maps API 为您提供了使用参数调用animateCamera方法的选项。zoom

const MapComponent= (props: any) => {

const map: LegacyRef<MapView> = useRef(null);

const onZoomInPress = () => {
    map?.current?.getCamera().then((cam: Camera) => {
        cam.zoom += 1;
        map?.current?.animateCamera(cam);
    });
};

return (
        <View>
            <MapView
                ref={map}
                provider={PROVIDER_GOOGLE}
                region={region}>
            </MapView>
            <ButtonComponent
                style={{position: 'absolute', bottom: 400, left: 0}}
                onPress={onZoomInPress}>
                Zoom In
            </MainButtonBlue>
        </View>
    );
}

Answer 4

//Example of Pinch to Zoom Image in React Native
//https://aboutreact.com/react-native-pinch-to-zoom-image/

//import React in our code
import React from 'react';

//import all the components we are going to use
import { SafeAreaView, StyleSheet, View } from 'react-native';

//import ImageViewer which will help us to zoom Image
import ImageViewer from 'react-native-image-zoom-viewer';

const App = () => {
  const images = [
    {
      url:
        'https://raw.githubusercontent.com/AboutReact/sampleresource/master/sample_img.png',
    },
    {
      url:
        'https://raw.githubusercontent.com/AboutReact/sampleresource/master/old_logo.png',
    },
  ];

  return (
    <SafeAreaView style={{ flex: 1 }}>
      <View style={styles.container}>
        <ImageViewer imageUrls={images} renderIndicator={() => null} />
      </View>
    </SafeAreaView>
  );
};

const styles = StyleSheet.create({
  container: {
    backgroundColor: '#F5FCFF',
    flex: 1,
  },
});

export default App;

Answer 5

这就是我所做的，对我来说效果很好：

function getRegion(origin, destination, zoom) {
  const oLat = Math.abs(origin.latitude);
  const oLng = Math.abs(origin.longitude);
  const dLat = Math.abs(destination.latitude);
  const dLng = Math.abs(destination.longitude);

  return {
      latitude: (origin.latitude + destination.latitude) / 2,
      longitude: (origin.longitude + destination.longitude) / 2,
      latitudeDelta: Math.abs(oLat - dLat) + zoom,
      longitudeDelta: Math.abs(oLng - dLng) + zoom,
  };                                                                                  
}