Flutter LatLngBounds 未显示准确位置

Question

我正在尝试使用我的扑扑谷歌地图将所有标记显示到视口中。但在我的情况下似乎不起作用。我已经尝试过如下：

    _controller.animateCamera(CameraUpdate.newLatLngBounds(
            LatLngBounds(
              southwest: LatLng(23.785182, 90.330702),
              northeast: LatLng(24.582782, 88.821163),
            ),
            100
        ));

    LatLngBounds boundsFromLatLngList(List<LatLng> list) {
    assert(list.isNotEmpty);
    double x0, x1, y0, y1;
    for (LatLng latLng in list) {
      if (x0 == null) {
        x0 = x1 = latLng.latitude;
        y0 = y1 = latLng.longitude;
      } else {
        if (latLng.latitude > x1) x1 = latLng.latitude;
        if (latLng.latitude < x0) x0 = latLng.latitude;
        if (latLng.longitude > y1) y1 = latLng.longitude;
        if (latLng.longitude < y0) y0 = latLng.longitude;
      }
    }
    return LatLngBounds(northeast: LatLng(x1, y1), southwest: LatLng(x0, y0));
  }

正如我所看到的，它总是显示北大西洋的地图 是否有关于此问题的任何解决方案，或者它刚刚在 Flutter 中开发？。提前致谢

Answer 1

当我使用CameraUpdate.newLatLngBounds. 设置边界后，它立即重新定位到北太平洋，不确定是什么原因造成的，但这里有一个解决方法 -

LatLngBounds您可以计算要设置的边界的中心，而不是使用设置地图位置

// the bounds you want to set
LatLngBounds bounds = LatLngBounds(
  southwest: LatLng(23.785182, 90.330702),
  northeast: LatLng(24.582782, 88.821163),
);
// calculating centre of the bounds
LatLng centerBounds = LatLng(
  (bounds.northeast.latitude + bounds.southwest.latitude)/2,
  (bounds.northeast.longitude + bounds.southwest.longitude)/2
);

// setting map position to centre to start with
controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
  target: centerBounds,
  zoom: 17,
)));
zoomToFit(controller, bounds, centerBounds);

将地图位置设置为边界中心（并放大）后，您需要继续缩小，直到可见地图区域覆盖您要设置的边界。您可以使用 获取可见的地图区域controller.getVisibleRegion()。这是实现 -

Future<void> zoomToFit(GoogleMapController controller, LatLngBounds bounds, LatLng centerBounds) async {
  bool keepZoomingOut = true;

  while(keepZoomingOut) {
    final LatLngBounds screenBounds = await controller.getVisibleRegion();
    if(fits(bounds, screenBounds)){
      keepZoomingOut = false;
      final double zoomLevel = await controller.getZoomLevel() - 0.5;
      controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
        target: centerBounds,
        zoom: zoomLevel,
      )));
      break;
    }
    else {
      // Zooming out by 0.1 zoom level per iteration
      final double zoomLevel = await controller.getZoomLevel() - 0.1;
      controller.moveCamera(CameraUpdate.newCameraPosition(CameraPosition(
        target: centerBounds,
        zoom: zoomLevel,
      )));
    }
  }
}

bool fits(LatLngBounds fitBounds, LatLngBounds screenBounds) {
  final bool northEastLatitudeCheck = screenBounds.northeast.latitude >= fitBounds.northeast.latitude;
  final bool northEastLongitudeCheck = screenBounds.northeast.longitude >= fitBounds.northeast.longitude;

  final bool southWestLatitudeCheck = screenBounds.southwest.latitude <= fitBounds.southwest.latitude;
  final bool southWestLongitudeCheck = screenBounds.southwest.longitude <= fitBounds.southwest.longitude;

  return northEastLatitudeCheck && northEastLongitudeCheck && southWestLatitudeCheck && southWestLongitudeCheck;
}