如何在 React Native map 中获得缩放级别

Question

I'm trying to calculate the zoom level when user zoom in or out,
I find that react native maps has a onRegionChange which has longiture, latitude, longitude delta and latitude delta which (I guess) could be used to compute zoom level
from this response I tried this way:

 Math.round(Math.log(360 / this.state.longitudeDelta) / Math.LN2);

but it return a big number (which is not the zoom level).

Answer 1

Write a function like below in the onRegionChangeComplete prop of react-native-map

changeRegion = debounce(async region => {
    console.log(
    Math.log2(360 * (metrics.screenWidth / 256 / region.longitudeDelta)) + 1
    );
  }, 1000);

or to be specific , Math.log2(360 * (metrics.screenWidth / 256 / region.longitudeDelta)) + 1); does the magic.

Answer 2

 <MapView onRegionChangeComplete={async (region) => { const coords = await ref?.current?.getCamera(); console.log('coords', coords.zoom); }} ref={ref} />

Answer 3

log2(360 * ((screenWidth/256) / region.longitudeDelta)) + 1